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ROBERT ADAMS
ST07002736
SCHOOL OF SPORT
UNIVERSITY OF WALES INSTITUTE, CARDIFF
THE EXTENT TO WHICH EXISTING LITERATURE AND RESEARCH
SUPPORTS HEALTHBOARD GUIDELINES ON DIFFERING EXERCISE
INTENSITIES AND TYPES AS A MEANS OF TREATING AND MANAGING
TYPE 2 DIABETES
TABLE OF CONTENTS
ACKNOWLEDGEMENTS – (i)
ABSTRACT – (ii)
CHAPTER ONE – Introduction – Page 1
CHAPTER TWO – Methodology – Page 5
CHAPTER THREE – Guidelines – Page 7
CHAPTER FOUR – The ‘FITT’ Principle – Page 11
CHAPTER FIVE – The Dose-Response Symposium – Page 13
CHAPTER SIX – Complications Of Type 2 Diabetes – Page 17
CHAPTER SEVEN – Translation Of Research Into Guidelines On Exercise –
Page 21
CHAPTER EIGHT – Discussion – Page 26
CHAPTER NINE – Conclusion – Page 29
Acknowledgements
I would like to thank Dr. Karianne Backx for her contribution in the provision of
relevant literature and research that enabled me to thoroughly conduct this study. I
would also like to thank the University of Wales Institute, Cardiff for providing me
with access to online databases through athens.ac.uk
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Abstract
Aims: The purpose of this study was to investigate the relationship between
exercise and type 2 diabetes. The specific aim of investigating the extent to which
guidelines for exercising type 2 diabetes patients are in agreement with the relevant
literature and research available on the management of type 2 diabetes through
prescribed exercise was developed. Methods: Health authority guidelines were
accessed via the individual health authority websites, while existing literature was
identified through a computerized search of an online database (athens.ac.uk). The
advice available to sufferers of type 2 diabetes from various health authorities
(Diabetes UK, National Health Service, American College of Sports Medicine) was
identified, the findings of existing research was scrutinized and the extent to which
there was continuity between the two was examined. Results: It was found that
guidelines advising low intensity exercise had their basis in relevant research and
literature. There were other areas of literature that were not covered in the guidelines
from health authorities; this was predominantly research that either concluded there
were no treatment benefits to be gained from exercise or that increased frequencies
and intensities of exercise can be used as a preventative measure against the
disease. Conclusions: It was concluded that although the guidelines from the health
authorities have their basis in relevant literature and research, there is still certain
levels of ambiguity surrounding certain modes of exercise as a treatment of type 2
diabetes due to the complications associated with the disease. Thus further
extensive research needs to be conducted to develop a definitive answer as to the
frequency, intensity, time and type of exercise that is most beneficial to type 2
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diabetes patients as well as a slight change of direction from the health boards to
direct some of their attention to prevent and not only treat type 2 diabetes.
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CHAPTER I - INTRODUCTION
Introduction
This study will be an investigation into the broad topic area of exercise and type 2
diabetes. The investigation will begin by outlining type 2 diabetes as an illness and
the resultant financial and health costs it has as one of the fastest growing illnesses
in the western world. The study will then focus in more detail on exercise as a means
of treating, managing and preventing the occurrence of the disease. Health board
guidelines will be identified and broken down into component parts relating to the
frequency, intensity, time and type of exercise that the health authorities recommend
for type 2 diabetes patients. A review of the relevant literature will identify what
current scientific recommendations are available for exercise and type 2 diabetes.
The relationship between the literature and the health authority guidelines will be
examined and conclusions made as to the relevance and effectiveness of the health
authority guidelines as a method of treating type 2 diabetes.
The increasing worldwide prevalence of type 2 diabetes, the cost of treatment and
the associated complications such as cardiovascular disease, vascular disease and
stroke, have been described as one of the most challenging health problems of the
21st century (Israili, 2009). In England alone, there are over two million people with
diabetes, with around 90% of these cases being type 2 diabetes (National Health
Service, 2009). The financial cost of the treatment and management of type 2
diabetes to health services and individuals is particularly significant. Studies have
shown that the cost of medical treatment is 1.8 times greater for patients with
diabetes than patients without and that a newly diagnosed, 50 year old type 2
diabetes patient has a medical expenditure that is US$4,174 higher than an identical
person without diabetes. Research has shown that this cost is also likely to grow
over time (Hylands and Trogdon, 2008).
Alright et al. (2001) proposed that there are both genetic and environmental, or
behavioural, factors that can predispose an individual to type 2 diabetes. The Expert
Committee on the Diagnosis and Classification of Diabetes Mellitus (1997) identified
that although there appears to be a genetic predisposition towards type 2 diabetes,
the exact genetic causes not yet well known. Hickey et al. (1995) defined old age,
obesity, minority ethnicity, family history and lower socio-economic status as the key
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environmental predisposing risk factors. The article by Albright et al. (2001) also
suggested that areas where body fat is mostly highly distributed, specifically if there
is a large amount of fat surrounding the intra-abdominal region, can be a better
predictor of type 2 diabetes than overall levels of obesity. The major behavioural risk
factors associated with type 2 diabetes were also identified by Albright et al. (2001),
with physical inactivity and poor diet being the main predisposing risk factors.
Type 2 diabetes is a form of diabetes where the pancreas is able to produce insulin,
unlike in type 1 diabetes where insulin production is restricted. In the case of type 2
diabetes, the body’s cells become unresponsive to the insulin that is produced
(Stensel and Hardman, 2003). However, the diagnosis of type 2 diabetes can be
difficult as patients can have the condition for a number of years before symptoms
begin to appear (Harris et al., 1992), thus general practitioners will usually screen
high risk patients for type 2 diabetes. Patients considered to be high risk are those
with either associated conditions (obesity, high blood pressure and hyperlipidaemia)
or complications associated with the disease such as cardiovascular disease or
retinal and renal conditions (Evans et al., 2003). The Expert Committee on the
Diagnosis and Classification of Diabetes Mellitus (1997) identified three new
diagnostic criteria that focused on microvascular complications that are specific to
type 2 diabetes. These criteria were designed to make diagnosis of type 2 diabetes
simpler for physicians. Matching only one of these criteria is considered sufficient for
a diagnosis of type 2 diabetes to be made. The criteria identified were:
1. A fasting plasma glucose level of 126mg.dL or above
2. Symptoms of diabetes, including polyuria, polydipsia and unexplained weight
loss in addition to a casual plasma glucose level of greater, or equal to
200mg.dL
3. 2 hour plasma glucose of 200mg.dL or more during an oral glucose test, using
75g of glucose
Albright et al. (2001) identified a number of diabetic complications as: retinopathy
(damage to the retina of the eye), peripheral neuropathy (nerve damage that affects
the extremities, in particular the lower legs and feet and can cause injuries or
infection), autonomic neuropathy (nerve damage that affects the autonomic nervous
system and interferes with heart rate regulation during exercise by decreasing
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maximum heart rate and blood pressure, while increasing resting heart rate),
nephropathy (kidney damage),
peripheral vascular disease, atherosclerotic
cardiovascular disease, cerebrovascular disease and hyper tension. Diabetes also
puts patients at an increased risk of contracting infections and periodontal disease.
There are a number of treatment methods for type 2 diabetes, including medication,
dietary improvements and prescribed exercise. As type 2 diabetes patients have an
increased risk of cardiovascular disease a primary concern is to control their blood
pressure. Therefore, antihypertensive drugs such as beta blockers, angiotensin
converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs)
have been recommended by the National Institute for Health and Clinical Excellence
(NICE) as medical treatment for hypertension in type 2 diabetes patients (Daly and
Purcell, 2003).
Dietary treatment for type 2 diabetes focuses on weight loss, as weight loss can
have a lessening effect on the impact of diabetes. It is recommended that diabetic
patients should minimise the amount of saturated fats, artificial trans fats, cholesterol
and sodium in their diet while increasing the amount of mono- and poly-unsaturated
fats, antioxidants and minerals such as potassium, magnesium and calcium in their
diet. It has also been suggested that a diet with a low glycemic index can be
beneficial in the management of type 2 diabetes (Melanson, 2007).
Combinations of medication and weight loss have been developed in recent years,
with anti-obesity medications being used, in conjunction with lifestyle modifications,
to aid weight loss and reduce obesity levels which are crucial factors in the
management and treatment of diabetic patients (Choussein et al., 2009).
Sibutramine is one example of anti-obesity medications, and was found to promote
satiety, thus minimising calorie intake and aiding in weight loss. Orlistat was also
found to aid weight loss and improve glycaemic status by inhibiting gastric and
pancreatic lipase production. Rimonabant was shown to have positive effects on
both weight loss and improvements in diabetic problems, such as blood glucose and
insulin levels. However, there were some side-effects noticed, with Sibutramine
having potential cardiovascular side-effects, Orlistat exhibited gastrointestinal sideeffects and Rimonabant was linked with psychiatric disorders and was temporarily
3
suspended as a commercial product. (Choussein et al. 2009). Therefore, the
prescription of anti-obesity medication needs to be carefully monitored by physicians
and healthcare professionals to avoid any side-effects, particularly from Sibutramine
developing into more serious diabetic complications.
Physical activity guidelines are also provided for type 2 diabetic patients by health
boards, organisations or charities such as the National Health Service (NHS),
American College of Sport Medicine (ACSM) and Diabetes UK and as a result, the
purpose of this paper will be to investigate the extent to which the existing literature
and research supports the physical activity guidelines that are provided for patients
with type 2 diabetes.
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CHAPTER II - METHODOLOGY
Methodology
This study involved the use of relevant journals to review the literature in the area of
exercise as a treatment of type 2 diabetes. This review of literature was then used to
critique the guidelines provided to exercising type 2 diabetes patients by various
health authorities. Peer reviewed journals were preferred to text books, as they
provide the most up to date and relevant research available.
In order to obtain the relevant literature required for this paper, a number of internet
searches were carried out to extract the information. The first internet search
involved using online databases, such as Ovid, SAGE Online, British Medical
Journal (BMJ), IngentaConnect and InformaWorld, accessed through MyAthens (an
educational service from Eduserv that allows institutions and students to access
online resources). The subscription and subsequent access to MyAthens was
provided by the University of Wales Institute, Cardiff (UWIC).
Key phrases and words relating to diabetes and the effect of exercise on diabetes
were used in the search process. As there were large numbers of results with each
search, a number of exclusion criteria needed to be applied to these results in order
to garner literature that was relevant to the topic of this review paper. Journals and
papers were only considered if they focused on the effects of exercise on the
management of type 2 diabetes, with the exception of a small number of papers
used in the introduction which focused on the cost, diagnosis, treatment (medical
and dietary) and incidence of type 2 diabetes. Articles were excluded if they were
non-English, as there was no capacity to translate into English, and if they were pre1990, due to the need for up to date and relevant literature.
The terms ‘diabetes’, ‘diabetes medication’, ‘diabetes diagnosis’ and ‘diabetes cost’
were entered into the Ovid Database which, with the help of the exclusion criteria,
yielded a total of 5 relevant journals. The keywords ‘diabetes diagnosis’, ‘diabetes
diet’ and ‘type 2 diabetes’ were entered into the SAGE Online Database, again
yielding 3 relevant journals. A search of ‘diabetes’ in the BMJ Database provided 1
journal, while one further source was provided from the reference list of an
aforementioned journal.
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The ACSM was used for a further search, which provided a Symposium on the
Dose-Response relationship between exercise and type 2 diabetes. Access to the
ACSM Database is not provided by Eduserv through MyAthens, thus permission and
access was granted by Dr. Karianne Backx, Lecturer of Physiology at UWIC. The
Dose-Response Symposium yielded a total of 5 review articles that were relevant to
the investigation. The reference list of each article was then examined for further
relevant literature, with a total of 21 further sources being deemed acceptable for use
in the study. No exclusion criteria were applied to research found through the
reference list of articles in the Dose-Response Symposium.
Finally, a search of health authorities was undertaken in order to find exercise
guidelines for type 2 diabetes patients that would be appropriate for the comparison
between relevant literature and health-board guidelines. The health authorities used
for their guidelines were the National Health Service, American College of Sports
Medicine and Diabetes UK. The National Health Service and Diabetes UK websites
both provided clear sections that outlined exercise guidelines for patients, while a
search of ‘diabetes exercise’ was required on the American College of Sports
Medicine website. There were no exclusion criteria, and all guidelines were
considered as relevant and acceptable.
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CHAPTER III - GUIDELINES
Guidelines
The National Health Service (2010) suggested that exercise alone may be enough to
control blood glucose levels in type 2 diabetes patients. However, it does indicate
that this is not always the case and that medical interventions may be needed and
even in cases where medicines are used as a treatment, exercise is still
recommended. Health authorities such as the National Health Service and American
College of Sports Medicine and charities including Diabetes UK provide exercise
guidelines for diabetic patients.
Diabetes UK
A recommendation of 30 minutes of exercise per day, 5 days a week was made for
adults. This was increased to a total of 60 minutes per day for children. A number of
low intensity activities were also recommended as possible ways of attaining the
required amount of exercise; these activities include walking, golf, cycling,
swimming, bowling and dancing (Diabetes UK, 2010(a)).
Furthermore, advice was provided for avoiding hypo- and hyperglycaemia (low and
high blood glucose levels respectively), which are conditions that can affect diabetes
patients as a result of exercise. This is due to excess or insufficient levels of insulin
to counterbalance the changes in blood glucose levels during, or after exercise
(Sandoval et al. 2004). Thus, adjustments may need to be made to insulin intake, in
consultation with a medical professional, before exercise (ACSM, 1995). Though it
was indicated that hypoglycaemia is a problem more associated with type 1
diabetes, it can also affect patients with type 2 diabetes.
Diabetes UK (2010(b)) recommended that to avoid hypoglycaemia patients should
direct injection sites away from the limbs that will be used in the activity, fast acting
carbohydrate snacks should be available during exercise, with slower acting
carbohydrates to be ingested during exercise that is strenuous and greater than an
hour in length.
To reduce the chance of suffering from hyperglycaemia, patients were advised not to
undertake any physical activity if blood glucose levels are above 14mmol/l before
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exercise or if there were ketones present in the urine. Diabetes UK (2010(b)) also
indicated that hyperglycaemia could be a result of not injecting enough insulin, which
means that the dominating effect of adrenalin causes an increase in the production
of glucose.
The final recommendation that was made by Diabetes UK was for patients to consult
with their General Practitioner (GP) before undertaking an exercise programme and
to take blood glucose levels more frequently, adjusting levels of medication, such as
insulin, as required.
National Health Service
Unlike Diabetes UK, the National Health Service isn’t solely focused on the
prevention and treatment of diabetes. Thus, only one section of the NHS website is
dedicated to information on diabetes, with an even smaller portion of this subsection
devoted to exercise as a treatment of diabetes.
There was congruence between guidelines from the National Health Service and
Diabetes UK, as the NHS also recommended that 30 minutes of exercise per day, 5
days a week (National Health Service, 2010). However, beyond defining exercise as
‘anything that gets you slightly out of breath and raises your heart rate’ there were no
further recommendations as to the type of exercise that a diabetic patient should
undertake.
There was also an agreement with the suggestion that patients should seek the
advice of a GP before embarking on an exercise programme and that insulin doses
may be adjusted for increased exercise levels with the help of a diabetic care team.
American College of Sports Medicine
The American College of Sports Medicine (2000) provided a set of guidelines with a
much greater level of detail than those from the National Health Service and
Diabetes UK. These guidelines made use of the Frequency, Intensity, Time and
Type (FITT) principle, splitting exercise into the categories of ‘aerobic’, ‘strength’ and
‘flexibility’.
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The recommendations made for aerobic exercise suggested that it should focus on
large muscle groups, be non-/low-weight bearing (such as swimming or using a cycle
ergometer) and involve cross training to reduce the chances of injury. Patients were
advised to exercise at an intensity of between 40-60% of their VO2 max or between
11 and 13 on the Rate of Perceived Exhaustion (RPE) scale for 40-60 minutes, 5
days a week. However, it was recommended that if the individual was taking insulin
then the intensity should be lowered and the time and frequency increased. The
American College of Sports Medicine also proposed that exercise should not
coincide with peak insulin activity.
Strength training should take the form of circuit, interval or free weight training. It was
recommended that these strength training sessions should be low resistance, high
repetitions – starting with 8-12 repetitions and progressing to a maximum of 20
repetitions per set. The ACSM also recommended limiting these sessions to 2 or 3
days per week.
The American College of Sports Medicine also advocated the use of a flexibility
regime to supplement aerobic and strength exercise. The flexibility sessions should
involve holding a stretch on a muscle group for 10-30 seconds, 2 or 3 days a week,
before or after aerobic or strength sessions.
The American College of Sports Medicine guidelines also provided precautions for
the exercising diabetic. They advised postponing exercise if blood glucose levels
were above 240mg.dL. It was also suggested that adjustments to carbohydrate or
insulin intake may be required 30-60 minutes before the start of exercise and that if
blood glucose is below 80mg.dL, then carbohydrates should be taken. It was also
noted that exercising late in the evening can result in an increased risk of nocturnal
hypoglycaemia, i.e. low blood glucose / high insulin levels at night, which can be
particularly dangerous as it isn’t possibly to rectify if the patient is asleep.
These guidelines from the ACSM provide a much more in depth description of the
exercise that a patient with type 2 diabetes needs to take, which will give the patient,
particularly one who is new to exercising, a much better idea of how they should go
about implementing an exercise regime. However, recommendations of performing
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at intensities of 40-60% VO₂ max or between 11-13 on the RPE may be unfeasible
due to a lack of appropriate equipment or physiological knowledge respectively.
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CHAPTER IV – THE ‘FITT’ PRINCIPLE
The ‘F.I.T.T’ Principle
Frontera (2007) suggested that effective exercise programmes should make use of
the F.I.T.T principle, which involves manipulating the frequency, intensity, time and
type of exercise used to maximise the effectiveness of the exercise programmes.
This principle can also be applied to the guidelines provided by health authorities to
determine the most effective exercise programme for diabetic patients from the
advice given.
Frequency:
The three health authorities (National Health Service, American College of Sports
Medicine, Diabetes UK) investigated for this paper were all consistent as their
guidelines suggested the frequency of exercise should be 5 times a week.
Intensity:
Information from the American College of Sports Medicine and Diabetes UK
suggested that a moderate intensity would be most effective for diabetes patients.
Diabetes UK suggested a number of activities, such as walking, swimming, cycling
or golf that would fall into this category, while the American College of Sports
Medicine recommended that intensity should be gauged as a percentage of VO₂ max
or on the Rate of Perceived Exhaustion scale. Meanwhile, the National Health
Service guidelines didn’t make any mention of intensity beyond a simple suggestion
that the exercise undertaken by patients should be anything that raises heart rate
and breathing levels.
Time:
Frontera (2007) identified that the timing of exercise is influenced by the intensity of
the exercise, i.e. a high intensity exercise could not be maintained for long periods,
while low intensity exercise should be undertaken in long periods in order to be fully
effective. With that in mind, as the general consensus from health boards is that
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exercise should be of moderate intensity, the time periods suggested are also
moderate. The National Health Service and Diabetes UK both suggested that 30
minutes of exercise is suitable, while the American College of Sports Medicine
advocated a slightly longer, yet still attainable at a moderate intensity period of
between 40-60 minutes.
Type:
The guidelines from Diabetes UK advised patients to undertake mainly whole body
or large muscle group, aerobic activities such as walking, dancing, cycling and
swimming. Similarly, the American College of Sports Medicine guidelines indicated
that large muscle, low weight bearing aerobic activities would be beneficial. In
addition to this, small amounts of low intensity strength resistance (such as circuit,
interval and free weight training) and flexibility training was suggested. Once more,
the National Health Service failed to provide any examples of the type of activity that
could be undertaken.
Using the F.I.T.T principle, it is apparent that the health bodies are, generally, in
agreement that a generic programme of moderate intensity aerobic exercise for circa
30 minutes a day, 5 days a week would be beneficial to most patients with type 2
diabetes.
The
American
College
of
Sports
Medicine
also
recommended
incorporating some strength and flexibility elements to supplement the exercise
programme, though the general consensus is for the use of aerobic activity.
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CHAPTER V – THE DOSE-RESPONSE SYMPOSIUM
The Dose-Response Symposium
The American College of Sports Medicine conducted a symposium on the ‘doseresponse’ of health to physical activity (2001). Howley (2001) defined ‘doseresponse’ as ‘the increasing levels of Physical Activity (PA) on changes in the levels
of a defined health parameter (e.g. risk factor, disease, anxiety level and quality of
life)’. Type 2 diabetes was among the various health parameters that were
investigated and the symposium investigated the favourable effects that varying
doses of exercise (i.e. F.I.T.T principle) can have on the disease.
The first article to focus on type 2 diabetes was by Albright et al. (2001). They found
that favourable changes in glucose tolerance and insulin sensitivity diminish after 72
hours of inactivity. Therefore, continued exercise is imperative to maintain positive
results in the control and management of type 2 diabetes. With this established,
Albright et al. (2001) suggested that patients should have a minimum energy
expenditure of 1000Kcal per week from physical activities. It was also found that
patients with diabetes have a lower physical fitness, specifically a lower VO₂ max,
and thus the intensity of their exercise should be lower – an RPE of 10-12 was
advised. For aerobic activities, walking was recommended as the most convenient
low-impact activity. This study also indicated that resistance training would be
beneficial to type 2 diabetes patients, with positive side effects such as an increase
in muscle strength and endurance, improved flexibility and improved body
composition noted. Risk factors for cardiovascular disease and improvements in
glucose tolerance and insulin sensitivity were also associated with resistance
training.
A number of other articles from the dose-response symposium provided evidence of
exercise as a good means of controlling and managing the problems associated with
diabetes. Bouchard and Boisvert (1999) identified that attaining an absolute energy
expenditure above 2Mj (Mega joules) per week was beneficial to sufferers of
diabetes and subjects with obesity. Meanwhile, Mayer-Davis et al. (1998) found that
there was a positive associated with insulin sensitivity for both vigorous (>6METS)
and non-vigorous (<6METS) activity, with METS being metabolic equivalent of task,
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a measure of exertion based on the ratio of metabolic rates during the activity to the
metabolic rates at rest.
Similarly to Albright et al. (2001), Oja (2001) investigated the effect of Kcal
expenditure per week on type 2 diabetes patients. Oja (2001) used a study by
Haapanen et al. (1997) to present their findings on the dose-response to diabetes.
Haapanen et al. (1997) conducted a 10 year prospective follow up study using 1340
men and 1500 women between the ages of 35 and 63. They then calculated the
relative risk of contracting type 2 diabetes for these participants based on their
weekly energy expenditure from leisure time, household tasks and physical activities.
Their findings indicated that males who were in the lower and middle third for energy
expenditure (0-1100Kcal.wk; 1101-1900Kcal.wk) had an increased, but non
significant risk of contracting diabetes. For females, the relative risk of contracting
diabetes was significantly increased and 2 fold for those in the lower third for energy
expenditure (0-900Kcal.wk). The upper third (>1500Kcal.wk) were found to have a
decreased risk of contracting diabetes when combining their normal weekly energy
expenditure with one weekly vigorous activity. These findings therefore suggest that
an increase in the ‘dose’ of physical activity can have a positive preventative effect of
diabetes.
Other research also identified that exercise was a preventative measure. Manson et
al. (1999) found that there was a decreased risk of diabetes for individuals who
undertook 3 hours of brisk walking per week. This is at odds with the findings of
Haapanen et al. (1999) which suggested that higher intensities of exercise are the
best preventative strategies, while brisk walking would only be considered low to
moderate in intensity. Meanwhile, earlier studies by Manson et al. (1991, 1992)
found that a more vigorous activity was needed to decrease the chances of diabetes
occurring. Manson et al. (1992) conducted a 5 year follow up study on males who
were free of diabetes, cardiovascular disease, stroke or cancer. The subjects
undertook vigorous activity (defined as vigorous by causing subjects to develop a
sweat) once a week, or more than once a week. They found a relative risk (RR) of
0.70 for those engaging in >1 vigorous activity per week, i.e. increased amount of
vigorous activity equalled a decreased chance of contracting diabetes. Manson et al.
(1991) also conducted an 8 year follow up study on females, following the same
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participant selection criteria and same research design. The relative risk of the
female group contracting diabetes was 0.84, which showed a slight increase in the
chance of developing the condition, yet still a positive relationship between high
intensity exercise and prevention of type 2 diabetes. Helmrich et al. (1991) also
conducted a follow up study (14 years) and found a 6% decrease in the incidence
rate of type 2 diabetesfor each 2.1Mj of energy expenditure per week.
The evidence from much of the dose-response symposium tends to suggest that
there is a dose-response for the prevention of diabetes, often with the intensity of the
exercise providing a greater decrease in the chances of contracting diabetes.
However, there appears to be less evidence for a dose-response for the
management of type 2 diabetes, which suggests that dietary and medical methods
may be better used as management of diabetes for patients who already suffer from
the disease, while exercise could better served as a preventative measure. Kelley
and Goodpaster (2001) drew similar conclusions, as they stated that it was unclear
as to whether there was a dose-response for improved glucose control, but that the
research suggested that an increase in physical activity led to an increased
prevention of diabetes. Research by Uusitupa (1996) and Poirier et al. (1996)
confirmed that exercise seemed to have little or no effect on glucose control in
diabetic patients. Uusitupa (1996) found that 3-4 weekly aerobic activities of between
30 and 60 minutes in length led to a 0.5% decrease in glycated haemoglobin
(HbA1c), though Kelley and Goodpaster (2001) identified that decreased levels of
HbA1c of between 0.5 and 1% were considered modest by the Food and Drug
Administration (FDA). Uusitupa (1996) also discovered that there was a decrease in
fasting plasma glucose and fasting insulin, but no change in insulin sensitivity from
the prescribed exercise intensity. Poirier et al. (1996) used a similar intensity
exercise programme over their 6 month intervention; with 3 weekly aerobic activities,
of 60 minutes in length and at 60% of VO₂ max. However, Poirier et al. (1996) found
even fewer indications that prescribed exercise resulted in improved long term
glucose control, as only fasting insulin levels were found to have decreased. Fasting
plasma glucose, HbA1c and insulin sensitivity all encountered no changes. However,
it is the opinion of Albright et al. (2001) that physical activity may be underutilized in
the management of type 2 diabetes. They believe this could be due to a lack of
15
understanding or motivation in patients, many of whom will be obese and leading
sedentary lifestyles, or due to a lack of clear recommendations and follow up by
healthcare professionals. Despite this, there is little evidence in their article to
suggest that this is the case.
The indications that there is no dose-response for glucose control in patients
suffering from diabetes may therefore suggest that the recommendations of health
authorities such as the National Health Service and Diabetes UK are correct to
suggest low intensity exercise as the best means of controlling diabetes, while the
recommendation of the American College of Sports Medicine to include resistance
training and some higher intensity activities may not be so beneficial. It may also be
prudent to note that the focus of the National Health Service advice revolves around
dietary and medicinal methods, which may be a more effective means of glucose
control according to Kelley and Goodpaster (2001).
16
CHAPTER VI – COMPLICATIONS OF TYPE 2 DIABETES
Complications of Type 2 Diabetes
Not all type 2 diabetes patients will be able to follow the recommendations provided
by the dose-response symposium due to various complications associated with the
disease that make exercise, and particularly intensive exercise a risk. Albright et al.
(2001) identified the main complications associated with type 2 diabetes as
retinopathy, peripheral and autonomic neuropathy, nephropathy, peripheral vascular
disease,
atherosclerotic
cardiovascular
and
cerebrovascular
disease
and
hypertension. They suggested that adjustments to the type and intensity of exercise
may need to be made for those with any of these complications and also advised
that the best method of reducing the risk of long term complications and controlling
glucose levels is to implement behavioural interventions with the inclusion of a
physically active lifestyle, i.e. the focus shouldn’t be entirely on the provision of
physical activity and exercise.
Neuropathy
Autonomic neuropathy is a complication of diabetes that affects the autonomic
nervous system. With reference to exercise, it interferes with heart rate regulation by
decreasing the attainable maximum heart rate and blood pressure, while increasing
resting heart rate (Kahn et al., 1986). Vinik (1995) identified that sufferers of
autonomic neuropathy present lower levels of fitness and fatigue at lower intensity
workloads. Therefore, it was suggested by Graham and Lasko-McCarthy (1990) that
physical activity for diabetic patients with autonomic neuropathy should be of a low
intensity and daily. These activities would ideally be able to accommodate only mild
changes in heart rate and blood pressure. Albright et al. (2001) suggested that due
to the issues surrounding heart rate response to exercise the intensity of activities
should be determined by the Rate of Perceived Exertion scale, rather than as a
percentage of the maximum heart rate or VO₂ Max
Peripheral neuropathy, while also affecting the nervous system, focuses on the
extremities with problems being particularly associated with the lower legs and feet.
The nerve damage can then lead to a loss of distal sensation, which in turn can lead
17
to musculoskeletal injury or infection (Green and Stevens, 1993). Due to the issues
surrounding the lower limbs, Graham and Lasko-McCarthy (1990) identified that
patients suffering from peripheral neuropathy should perform non-weight bearing
activities in order to minimise irritation and trauma to the lower legs and feet. The
American College of Sports Medicine (1995) recommended that stationary cycling
(using an ergometer), swimming or other water based activities would be the most
effective forms of non-weight bearing exercise.
Hypoglycaemia
Although not identified by Albright et al. (2001), hypoglycaemia can be an issue for
type 2 diabetes patients. Wasserman and Zinman (1994) found that moderate
intensity exercise increases glucose uptake by 2-3mg per kilogram of body mass per
minute, while high intensity exercise increases glucose uptake by 5-6mg.kg.min
which therefore puts diabetic patients at an increased risk of hypoglycaemia,
particularly at higher intensities of exercise. The American College of Sports
Medicine (1995) produced a number of guidelines in order to minimise the risk of
hypoglycaemia. They suggested that patients intending to exercise need to
understand the relationship between exercise and the timing of medication, the preand post-exercise nutrition and their last blood glucose assessment. Patients were
advised to direct insulin injections, should they be needed, away from areas of the
body that will be active during exercise and at least an hour before exercise, which is
in accordance with the guidelines of Diabetes UK (2010). The final recommendation
of the American College of Sports Medicine is to consult with healthcare
professionals about trying to reduce medication and increase carbohydrates before
exercise, though it is noted that they suggested a decrease in medication was
preferable to an increase in calories and carbohydrates.
Cardiovascular Disease
Waxman and Nesto (1995) found that patients with type 2 diabetes were also at a
significantly increased risk of contracting cardiovascular disease. Male sufferers of
diabetes were found to have a 50% increased chance of a myocardial infarction,
18
while in females this was increased to a 150% greater chance of a myocardial
infarction.
Meanwhile, the American Heart Association Writing Group (1995) made some
exercise recommendations for those with cardiovascular complications. It was
suggested that moderate intensity activities of between 60-80% maximum heart rate
or between 50-74% VO₂ Max would be the most effective form of type 2 diabetes
management.
Hornsby (1995) also provided advice on resistance training should diabetes patients
with cardiovascular complications wish to begin or continue with resistance training.
They recommended that a lower lifting intensity should be undertaken, while
avoiding the temptation to exercise to exhaustion. It was also suggested that
individuals should eliminate sustained periods of gripping and performing isometric
contractions as this may put undue stress and strain on aspects of the
cardiovascular system.
Retinopathy
In their study, Vranic and Berger (1979) concluded that despite the fact that exercise
increases systematic and retinal blood pressure, there is no evidence that physical
activity acutely worsens retinopathy occurring in diabetes patients.
However, more recent research by Hornsby (1995) recommended adjusting the
levels and intensity of exercise to minimise the risk of exacerbating the problem of
retinopathy. They provided the same recommendations for sufferers of retinopathy
as they did for those with cardiovascular complications, i.e. to have a lower lifting
intensity, to avoid exercising to exhaustion and eliminating sustained gripping and
isometric contractions.
The research tends to suggest that for those with long term complications of
diabetes, high intensity exercise puts them at increased risk and thus the amount
and intensity of prescribed exercise should be lowered and the type of exercise
19
altered to avoid the risk of problems escalating. Therefore, medical and dietary
interventions, combined with some physical activity, appear to be more effective
means of controlling type 2 diabetes for those suffering from long term
complications. This appears to be in agreement with the some of the findings of the
dose-response with regards to exercise for the management of diabetes.
20
CHAPTER VII – TRANSLATION OF RESEARCH INTO GUIDELINES ON
EXERCISE
Translation of Research into Guidelines on Exercise
Once research has been conducted, it needs to be translated into credible guidelines
on exercise and the hazards of exercise for diabetic patients. Having investigated the
dose-response symposium and the complications of diabetes in relation to the doseresponse symposium, this section will now examine the relationship between the
research, the guidelines and the way in which the guidelines have been developed
from the existing literature and research.
Diabetes UK
The first exercise guideline identified by the charity Diabetes UK (2010) was that
exercise should be undertaken for 30 minutes, 5 times a week. Research by Albright
et al. (2001) appears to be the basis for these guidelines. They recognized that there
are significant acute benefits to be had from exercise, namely improved glucose
tolerance and insulin sensitivity. However, these benefits were also found to diminish
72 hours after the completion of exercise. It was found that if exercise was continued
at regular intervals, these benefits are maintained but with the addition of chronic,
long term benefits such as weight loss, decreased body fat, decreased
cardiovascular disease risk factors and improved aerobic fitness.
Diabetes UK (2010) then went on to recommend that walking and other low to
moderate intensity activities such as swimming, cycling, golf and dance would be
beneficial. Albright et al. (2001) provided research to back up these guidelines, as
they suggested that walking may be the most convenient low impact activity for
diabetic patients. They also indicated that some patients, due to suffering from
peripheral neuropathy, may require non-weight bearing activities such as swimming
and other water based activities or stationary cycling to negate the potential lower
limb and foot problems. This suggestion of low to moderate activities that are either
low- or non-weight bearing indicates concurrence with a number of articles, including
Graham and Lasko-McCarthy (1990) and Vinik (1995), that suggested exercising at
higher intensities may not be beneficial in the treatment of diabetes and more
importantly, may even exacerbate diabetic complications.
21
The next guideline from Diabetes UK (2010) suggested that insulin injection sites, if
required, should be directed away from areas that would be the predominantly active
muscle groups during exercise. The evidence for these suggestions came from the
American College of Sports Medicine (1995) who identified injecting insulin 1 hour
before exercise and away from active areas as one of the methods of reducing the,
albeit small, risk of type 2 diabetes patients contracting hypoglycaemia.
The final recommendation of Diabetes UK (2010) was that patients should consult
with their General Practitioner before embarking on an exercise or training
programme, similarly when adjusting medication levels. Albright et al. (2001) also
provided the evidence to reinforce these guidelines by asserting that ‘any exercise
programme should be physician approved’.
National Health Service
As previously identified, the National Health Service (2010) devoted very little of their
advice to exercise as a means of treating and managing type 2 diabetes and
subsequently much of their advice was very basic. Similarly to Diabetes UK (2010),
the National Health Service (2010) suggested that exercise should be in 30 minute
blocks, 5 days a week and that a General Practitioner should be consulted before
initiating an exercise programme. Likewise, evidence for these guidelines can be
found in Albright et al. (2001).
Though no specific activities or intensities are suggested, the F.I.T.T principle would
suggest that 30 minutes of exercise would equate to low to moderate intensity. This,
like the advice from Diabetes UK (2010), may be an acknowledgement that higher
intensities of exercise are not as effective at treating diabetes (Uusitupa, 1996) and
may cause complications of the disease, such as cardiovascular disease and
neuropathy, to escalate.
The National Health Service (2010) did, however, advise that insulin, or indeed other
medication doses may be adjusted prior to exercise. As with guidelines from
Diabetes UK (2010), evidence for the adjustment of medication comes from the
American College of Sports Medicine (1995) instructions for decreasing the risk of
22
contracting hypoglycaemia; they suggested that patients should consult with
healthcare professionals to reduce medication or increase carbohydrates in order
that blood sugar levels don’t drop to dangerous levels, though the American College
of Sports Medicine (1995) indicated that decreasing the doses of medication was
preferable to ingesting an increased amount of carbohydrate before exercise that
may cause blood glucose levels to rise.
American College of Sports Medicine
The American College of Sports Medicine (2000) guidelines also begin with a
recommendation that activity needs to be undertaken 5 days a week, which once
again can be evidenced by Albright et al. (2001) who found that continued exercise
is important to maintain acute benefits and encourage the development of the
chronic benefits of exercise. There is also the suggestion that patients should focus
on exercising large muscle groups in non- or low-weight bearing activities. This can
also be supported by the article written by Albright et al. (2001) which identified
walking, swimming and stationary cycling as ideal activities to avoid exacerbating or
developing diabetic complications such as peripheral neuropathy.
The American College of Sports Medicine (2000), unlike the National Health Service
and Diabetes UK (2010) identified specific intensities that sufferers of type 2
diabetes should aim for when exercising. Specifically, patients were advised to
exercise at between 40-60% of VO₂ Max or between 11 and 13 on the Rate of
Perceived Exhaustion (RPE) scale. The American Heart Association Writing Group
(1995) devised an intensity recommendation of 50-74% VO₂ Max, which supports
the advice of the American College of Sports Medicine. However, the American
Heart Association Writing Group (1995) did identify that this intensity was best for
those with cardiovascular disease, though this is a complication that effects a large
number of type 2 diabetes patients (Evans et al., 2003). Meanwhile, Albright et al.
(2001) found that a Rate of Perceived Exhaustion of between 10 and 12 to be most
effective for patients attempting to manage their illness. They also identified that
Rate of Perceived Exhaustion may be a better indicator of intensity, as many
diabetes patients are sufferers of autonomic neuropathy which effects heart rate
23
regulation during exercise meaning that heart rate readings may not be an accurate
representation of the actual intensity of exercise. However, there were no indications
in the American College of Sports Medicine guidelines that working to the Rate of
Perceived Exhaustion would be a better option than using VO₂ Max as an indicator
of exercise intensity.
The ‘F.I.T.T’ principle is also used by the American College of Sports Medicine
(2000) guidelines, which is in agreement with the overall theme of the dose-response
symposium, which suggested that adjusting the frequency, intensity, time and type of
exercise can have positive effects on various health issues. The American College of
Sports Medicine (2000) also made the point that exercise shouldn’t coincide with
peak insulin activity, which indicates there is congruence between the three health
authorities.
The evidence for this advice can also be found in research by the
American College of Sports Medicine (1995) that discovered that insulin injections
should be made an hour before exercise, or the level of insulin reduced in
consultation with healthcare professionals in order to reduce the risk of
hypoglycaemia.
Resistance training was also recommended by the American College of Sports
Medicine (2000), with low weight and high repetitions being the preferable mode of
resistance training. It was indicated that 8-12 repetitions were ideal, building to a
maximum of 20 repetitions. This advice is taking a different direction to that of the
National Health Service and Diabetes UK (2010), neither of whom recommended
implementing resistance training. However, there is some evidence from Hornsby
(1995) that resistance training can be effective. They also identified that lower lifting
intensities were preferential, mostly due to retinal and cardiovascular complications
that patients might be suffering from and also might be irritated by heavy lifting,
working to exhaustion and sustained gripping and isometric contractions.
The final exercise guideline from the American College of Sports Medicine (2000)
was that a flexibility regime, consisting of stretching each muscle group for 10-30
seconds, 2 or 3 days a week, should be included into an exercise programme
consisting of both aerobic and strength training. There is little evidence in the dose-
24
response symposium to suggest that flexibility training can have any specific benefit
for type 2 diabetes patients. However, Nobrega et al. (2005) identified that good
levels of flexibility are required for efficient movement and optimising sports
performance, which may indicate that the American College of Sports Medicine
(2000) guidelines included a flexibility regime merely to supplement and improve the
quality of the aerobic exercise.
The majority of guidelines from the various health boards come from research
focusing on the adjustments made to exercise types and intensities for persons with
diabetic complications. This would indicate that the National Health Service,
Diabetes UK and the American College of Sports Medicine are aware that increased
intensity of exercise is better as a preventative measure and that as their existence
is to treat people who have already contracted diabetes, who may in turn suffer from
one of the numerous and dangerous health complications associated with type 2
diabetes. Thus, they have advocated decreasing intensity of exercise, adjusting the
type of exercise to account for those who suffer from peripheral neuropathy and the
use of dietary and medicinal methods in conjunction with the exercise.
25
CHAPTER VIII – DISCUSSION
Discussion
The major findings of this study suggest that there is congruence between the
guidelines of three major health authorities (National Health Service, Diabetes UK,
American College of Sports Medicine) and research into the exercise adjustments
needed for individuals exhibiting complications of type 2 diabetes, which tends to
suggest that low to moderate intensity activities provide the most benefit with the
least risk. There is little agreement between the guidelines and research that
advocates the use of high intensity exercise as a treatment of type 2 diabetes.
The majority of the suggestions for frequency, intensity, time and type of exercise
from the health authorities can be found in this research into exercise and
complications of type 2 diabetes. Though there is no explanation as to why these
guidelines have been provided, it is clear that the directive of the health authorities is
to assist all type 2 diabetes patients, thus the guidelines need to be suitable for all
diabetes patients, regardless of complications that they may or may not have. It is for
this reason that the guidelines focus mainly on low intensity, low- or non-weight
bearing exercise that will avoid exacerbating complications such as neuropathy or
cardiovascular. The guidelines also recommend consulting physicians before
embarking on exercise programmes, so there is freedom for those without
complications to undertake high intensity exercise should they wish, though it must
be noted that research indicates that higher intensity exercise is more beneficial as a
preventative measure rather than as a treatment or management strategy.
The results of this investigation are in agreement with Albright et al. (2001) who also
investigated the effects of exercise on the treatment and management of type 2
diabetes. They found numerable benefits were to be had for the diabetic patient from
exercising regularly and at a low intensity, many of which were benefits included in
the guidelines from the health authorities. However, Albright et al. (2001) also
indicated that physical activity is underutilized in the management of type 2 diabetes,
either due to a lack of motivation on behalf of the patient or a lack of exercise
prescription and subsequent follow-ups from healthcare professionals. This may
indicate that the health authorities, particularly the National Health Service whose
exercise guidelines were minimal, should consider devoting more time and attention
26
to their advice on exercise as it may prove to be more beneficial to type 2 diabetes
patients.
There may also be alternative explanations for the reason behind the agreement
between guidelines and research. It’s not unreasonable to suggest that the health
authority guidelines are general guidelines for an improved lifestyle, rather than
specific recommendations to aid the treatment of type 2 diabetes. Certainly, the
National Health Service guidelines for diabetic patients are identical to their advice
for non-diabetic patients, i.e. 30 minutes of physical activity, 5 days a week. There is
evidence from research that this may be the case, as Kelley and Goodpaster (2001)
found that it was unclear whether there was any exercise dose-response for
improved glucose control and that many trials include both dietary and exercise
interventions, thus making it hard to determine the true effect of exercise as an
influencing factor in the improvement of type 2 diabetes. They also identified that
increased levels of physical activity are better used as a prevention of type 2
diabetes. Similarly, Uusitupa (1996) found little benefit to be had from exercise for
type 2 diabetes patients. Over the course of a 12 month intervention it was found
that diabetic patients who performed 3-4 moderate aerobic activities of between 30
and 60 minutes had only modest reductions in glycated haemoglobin, fasting plasma
glucose and fasting insulin, while there were no changes in insulin sensitivity. Poirier
et al. (1996), meanwhile, found only a modest change in fasting insulin levels and no
changes in glycated haemoglobin, fasting plasma glucose and insulin sensitivity from
3 weekly aerobic activities at 60% VO₂ Max for 60 minutes. This research may
therefore be an indication that the exercise guidelines from the health authorities are
general exercise guidelines for an overall improved healthy lifestyle, rather than
specific diabetes instructions.
The findings of this study have significant implications for type 2 diabetic patients.
There is relevant and current advice provided for type 2 diabetes patients on how
best to use exercise as a treatment method, while the findings also suggest that the
health authority guidelines aren’t unfounded pieces of advice, but have their basis in
relevant, peer reviewed literature.
27
This investigation does have some limitations with the design and way the
investigation was conducted. The initial limitation that can be observed is that there
was a narrow range of sources used as the basis of the research and literature.
There were also issues with the type of research used. Many of the studies and
papers that were examined in the investigation were vastly different in design and
implementation. There were numerous methods of measuring intensities of exercise,
as well as many different modes of exercise used in the studies which makes it hard
to draw definitive conclusions on specific exercise modes that are beneficial to
sufferers of type 2 diabetes. Finally, very few of the studies in the research on
adjusting exercise based on the complications of type 2 diabetes focused on the
same complications.
There is also an obvious need for continued research into the role that exercise can
play in the treatment and management of type 2 diabetes. The identification of the
limitations of this study provides an indication of the direction that further research
should take. New research designs, given enough time and funding may need to use
patients who are suffering from more than one diabetic complication, or failing that
use a larger participant base so that numerous complications are covered in the
study. Patients who don’t exhibit any complications may also be used as a control
group in the studies. A large number of exercise types and intensities can then be
introduced to the subjects throughout the study with variables such as glycated
haemoglobin, fasting plasma glucose, insulin sensitivity and fasting insulin levels
being monitored over the course of the activity programme to determine if there are
any permanent, positive effects from the physical activity. This would require a long
length intervention study, ideally over the course of a number of years to allow for
the effects of different exercise modes to be thoroughly documented. However the
results could determine whether there is a definitive frequency, intensity, time and
type of exercise that is beneficial to the majority of diabetic patients. If this was not
the case, there would almost certainly be evidence of the ideal exercise programme
for each type of complication, which would enable health authorities to provide
extensive and detailed guidelines, which would then in turn enable type 2 diabetes
patients to manage their disease more effectively and lead a more normal, healthy
lifestyle.
28
CHAPTER IX – CONCLUSION
Conclusion
The results of this study therefore conclude that health authority guidelines
investigated in this article are supported by some, if not all, of the relevant literature
in the field of exercise as a means of treating and managing type 2 diabetes which
can be a point of reassurance for type 2 diabetes patients that the advice they are
following is evidenced by scientific research. The recommendations of Diabetes UK,
the National Health Service and the American College of Sports Medicine all have
their basis in research, much of which has been detailed by the Dose-Response
symposium conducted by the American College of Sports Medicine (2001).
There were, however, other studies that did not endorse the claims made by the
health authorities, some of which, including studies by Uusitupa (1996), Poirier et al.
(1996) and Kelley and Goodpaster (2001), maintained that the benefits of exercise
as a treatment for type 2 diabetes patients were negligible beyond the normal
expected health benefits.
Other studies such as Oja (2001) and Haapenen et al. (1997) concluded that high
intensity exercise combined with positive changes in lifestyle and diet served as the
best means of preventing type 2 diabetes, though there is no mention of this in any
of the health authority guidelines that were investigated. The idea of aiding in the
prevention, as well as the treatment, of type 2 diabetes could be an area that the
relevant health authorities could implement in future, as reducing overall incidence of
the disease has been identified as a major health concern of the modern age (Israili,
2009) not only because of the overall cost of health but also due to the escalating
financial cost of treating type 2 diabetes ( Hylands and Trogdon, 2008).
The final conclusion of this study must be that although there is some agreement
between research and guidelines, there are areas that still provide some uncertainty,
and consequently further research needs to be undertaken to provide definitive
answers, specifically answers that allow clear and precise exercising guidelines with
regards to the frequency, intensity, time and type to be outlined for all type 2
diabetes patients. There should also be indications from the National Health Service,
Diabetes UK and American College of Sports Medicine of the benefits of adopting a
29
healthy lifestyle and undertaking high intensity activities in preventing the occurrence
of type 2 diabetes. As health authorities it should be their obligation to not only treat
type 2 diabetes as and when the illness occurs but also to educate at-risk individuals
in order to prevent the increasing incidence levels of the disease.
30
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