Download A Correlat Study

Original Article
Thai Journal of Physiological Sciences
Vol. 21 No. 2 Oct. 2008-Mar. 2009
A Correlative Study of BMI and IOP in Diabetic and Nondiabetic
South Indian Population
Sheila Pai1, Shobha Pai2, Ashwin Pai3, Ramasamy C1, Rekha D Kini1
ABSTRACT
Diabetes is a risk factor for POAG (primary open angle glaucoma), a second leading cause for legal
blindness. Elevated intraocular pressure, a main risk factor for glaucoma, is a concern in diabetics. IOP
(Intraocular pressure) has been associated with various systemic, familial, anthropometric and demographic factors by several studies. There has been no study relating these factors in diabetes in particular.
This study was undertaken to find out the effect of BMI on intraocular pressure in subjects with diabetes.
101 subjects, 65 diabetics and 36 nondiabetics, aged 40-70 yrs attending diabetes check facility at KMC
(Kasturba Medical College) hospital were included. Hypertensives, known diabetics undergoing treatment, glaucoma, or receiving IOP-lowering treatment, ocular diseases were excluded. Participants underwent standardized examinations including applanation tonometry and anthropometric indices. Intraocular pressure (IOP) was assessed in both eyes using Goldmann applanation tonometer and recorded as the
average of three measurements. Subject’s height, weight in kilograms was measured. BMI was calculated
as weight in kilogram / (height in m)2. Statistical analysis was done by Student’s t-test. The mean IOP
±3.05)
(19.7±
±1.64 mmHg) in diabetics was higher than the nondiabetics (p<0.0001). The mean BMI (23.13±
in diabetics was higher than nondiabetics (p<0.003). A significant trend in increase in IOP to increase in
BMI was observed when different grades of BMI were compared. A significant correlation was found
between BMI and IOP (p<0.0001). The diabetics have higher IOP and higher BMI. The BMI is associated with increased IOP in subjects with diabetes.
Key words:
Diabetes, Body Mass Index, Intraocular Pressure, glaucoma
INTRODUCTION
with diabetes - a number that is predicted to increase to
around 80 million by 2030. Diabetes mellitus is an important ocular risk factor. People with diabetes are 25
times more likely to become legally blind than those without diabetes. Diabetes as a pre-existing condition also
increases the risk of glaucoma, the second leading cause
of visual impairment and blindness. Many studies have
suggested an increase in the relative risk of people with
diabetes mellitus to present ocular hypertension during
the clinical course of the disease favoring the emergence
of open angle glaucoma1,2, Evidence of an association
between primary open-angle glaucoma and diabetes is
conflicting.
The potential association between diabetes and pri-
Diabetes is one of the world’s greatest health challenges and its prevalence appears to be increasing. India
is already a world leader, with over 35 million people
1
Dept.of Physiology, Kasturba Medical college, Mangalore
Dept. of Ophthalmology, KMC, Mangalore.
3
Dept. of Ophthalmology, KMC, Mangalore.
Address for Correspondence
Dr. Sheila R Pai
Department of Physiology, Center for Basic Sciences
Kasturba Medical college, Bejai, Mangalore- 575004,
Karnataka, India.
Email: [email protected]
Phone number:91 9448109840
Fax: 91 824 2428 183
2
74
Sheila Pai, et al.
A Correlative Study of BMI and IOP in Diabetic and Nondiabetic South Indian Population
mary open angle glaucoma (POAG) has been studied by
many groups3, with most studies supporting a weak association between the two diseases4,5. Some have failed
to confirm an association between diabetes mellitus and
primary open angle glaucoma and ocular hypertension.4
Elevated IOP is a major significant risk factor for the
development of POAG.5 Although the link between diabetes and POAG is not clearly understood, data show
that diabetes may increase the risk of POAG by elevating
IOP. Elevated IOP is a concern in people with diabetes
as it is one of the main risk factors for glaucoma. IOP is
the only modifiable risk factor. It needs to be assessed
concurrently with other risk factors.
Several studies have reported factors including
5-8
age , sex4, African ancestry4, blood pressure11, BMI10,
alcohol, smoking, myopia and family history of glaucoma
to be positively associated with elevated IOP in general
population. Till date there are no evidences correlating
the effect of these parameters with elevated IOP in diabetes. Hence this study was undertaken to evaluate the
effects of body mass index on elevated intraocular pressure (IOP) in diabetes, in South Indian population who
are, ethnically, prone to develop diabetes.
assessed in both eyes using Goldmann applanation
tonometer and recorded as the average of three measurements. Subject’s height, weight in kilograms, blood
pressure and pulse rate were measured. BMI was calculated as weight in kilogram / (height in m)2.
Statistical analysis
All data are expressed as means ± standard deviations. Statistical analysis was done by Student’s t-test
and Pearson correlation coefficients. The p-values less
than 0.05 were considered statistically significant
RESULTS
Selected characteristics of the study are shown in
Table 1. When IOP was compared between subjects
with diabetes and those without diabetes, it was found
the diabetics exhibited a statistically significant higher
IOP compared to their counter parts (p<0.0001). Comparison of BMI between diabetics and nondiabetics
showed a significant higher BMI in the diabetics to the
nondiabetics (p<0.003).
To evaluate the relation between BMI and IOP,
The subjects were categorized into 3 groups (group I
with BMI<20, group II with BMI 20-25 and group III
with BMI>25). In diabetics, IOP showed a statistically
significant increase with BMI (Table 2). There was significant increase in IOP (p<0.01) when group II was
compared with group I. Similarly, IOP was also significantly high (p<0.01) when group III was compared with
group I. A significant high IOP (p<0.05) was also observed when compared between group II and group III.
When the IOP in diabetic males and females were compared no statistically significant difference was found in
all the 3 groups. Among the diabetic male subjects a
statistically significant difference in IOP was seen only
between group III and group II (p<0.05) and group III
and group I (p<0.05). Among the diabetic female sub-
MATERIAL AND METHODS
101 subjects, aged between 40-70 years out of
which 65 were diabetics and 36 nondiabetics (control
group) who underwent comprehensive medical checkup
in a diabetes check facility at KMC hospital, Mangalore
were included in our study after obtaining their consent.
Exclusion criteria included hypertensive, known diabetics undergoing treatment, glaucoma or receiving IOPlowering treatment, ocular diseases. Participants underwent standardized examinations including applanation
tonometry, measurement of blood pressure, and anthropometric indices, Ocular examinations including visual
acuity and funduscopy. Intraocular pressure (IOP) was
Table 1. Comparison of variables between Diabetics and Nondiabetics
Variables
IOP (mmHg)
BMI
Diabetics (n=65)
Non Diabetics (n=36)
mean ± SD
mean ± SD
19.7 ± 1.64
23.13 ± 3.05
18.0 ± 1.68
21.31 ± 2.37
75
p value
p<0.0001
p<0.003
Vol. 21 No. 2 Oct. 2008-Mar. 2009
TJPS
Table 2. Correlation between BMI and IOP in diabetics
IOP (mmHg) mean ± SD
BMI
Group I
BMI <20
Group II
BMI 20-25
Group III
BMI >25
Male
Female
Total
(n=2)
18±0
(n=21)
19.43±1.57
(n=7)
20.86±1.57*§
(n=3)
16.67±2.31
(n=24)
19.58±1.44§§
(n=8)
20.25±1.28¶¶
(n=5)
17.6±2.19
(n=45)
19.6±1. **
(n=15)
20.53±1.41**,■
**p<0.01, Gr II & Gr III versus Gr I
■
P< 0.05, Gr III versus Gr II
*P<0.05, Gr III versus Gr II
§
P<0.05, Gr III versus Gr I
§§
P< 0.01, Gr II versus Gr I
¶¶
P<0.01, Gr III versus Gr I
Table 3. Correlation between BMI and IOP in diabetics and nondiabetics
IOP (mmHg)
mean ± SD
BMI
Group I
BMI <20
Group II
BMI 20-25
Group III
BMI >25
tion was more significant in diabetic females (p<0.001)
than in males (p<0.01). Contrary to this, in nondiabetics
the correlation was not significant.
Diabetics
Nondiabetics
DISCUSSION
(n=5)
17.6±2.19
(n=45)
19.6±1. 0
(n=15)
20.53±1.41
(n=10)
17.05±1.80 NS
(n=20)
18.55±1.54**
(n=6)
17.5±1.0***
Diabetes mellitus (DM) is a risk factor for openangle glaucoma, although the mechanistic interrelationship of the two is debatable. Newly diagnosed diabetes
mellitus and high levels of blood glucose are associated
with elevated IOP and high-tension glaucoma. The development of glaucomatous optic nerve damage, based
on visual field loss and/or optic disc findings, is more
likely to be associated with high intraocular pressure
(IOP).3
Diabetics seem to have higher intraocular pressures
and may have a higher rate of glaucoma than those without diabetes4. The mean intraocular pressure in maturity onset diabetes was 19.26 mm of Hg which was higher
than the normal mean intraocular pressure reported in
the general population by Becker was 16.1 mm of Hg18.
Klein et al8 and others1,3,4,8,17,20 have observed a slightly
higher mean IOP among the diabetic participants than
the no diabetic comparison group. The finding in the
present study clearly indicates a higher mean IOP (19.7
± 1.64 mmHg) in diabetics as compared to the nondiabetic population (18.0 ± 1.64 mmHg) and is consistent with these studies.
However it is not in agreement with the reports of
NS= Not significant, D.Gr I versus ND.Gr I
**p<0.01, D.Gr II versus ND.Gr II
***p<0.001, D.Gr III versus ND.Gr III
jects, a significant increase in IOP was observed when
group II was compared with group I (p<0.01). There
was a significant increase in IOP when group III was
compared with group I (p<0.01).
When IOP was related to BMI and compared between subjects with diabetes and without diabetes (Table
3), in group I there was no significance observed. The
IOP in group II and group III showed a significant increase (p<0.01 and p<0.001) respectively in diabetics
compared to nondiabetics. Correlative analysis showed
a very statistically significant association between BMI
and IOP in diabetic subjects (p<0.0001). The correla-
76
A Correlative Study of BMI and IOP in Diabetic and Nondiabetic South Indian Population
Palomar16, Armaly and Baloglour17 who observed low
IOP in diabetics as compared to nondiabetics. A few
early studies found no evidence of increased pressure in
diabetes13-15 and one study found evidence of lower pressures16. Although etiologic links between IOP and diabetes remain unclear, several hypotheses have been advanced. Genetic factors are likely to play a role. There is
also evidence that diabetes-related autonomic dysfunction is likely to increase IOP. A cellular basis for the
higher IOP in diabetes was related to accumulation of
fibronectin in trabecular meshwork tissue22.
When BMI was evaluated, it was found that the
mean BMI in diabetics was 23.13 ± 3.05 and the mean
BMI was 21.31 ± 2.37 in nondiabetics. The BMI was
significantly higher in diabetics than those without diabetes (p<0.003). A trend of increasing IOP with increasing BMI was observed in diabetics which was statistically significant. BMI was positively correlated with
increasing IOP (p<0.0001 ) in diabetic subjects. A significant association was also observed in both sexes. In
non diabetics there was no significance found between
BMI and IOP.
Obesity is an established determinant of diabetes
which is associated with elevated IOP. The relationship
between an increased BMI and IOP has been well established. The Barbados Eye Study found larger body size,
as measured by BMI, was associated with increasing IOP3.
Although obesity is related to diabetes, the association
between BMI and IOP was an independent factor (Barbados Eye Study). A relation between obesity and IOP
was also found in studies by Shiose et al.6,7, Klein et al.8
and Bulpitt et al.19 in their Japanese, American and British populations respectively. An association between
obesity and IOP was also found in the Japanese population by Keiko Mori4. Moreover, some epidemiological
studies examined the relationship between obesity and
IOP cross-sectionally and have found that obesity was
an independent risk factor for increase in IOP, even when
considered with age, systolic blood pressure (SBP) and
diastolic blood pressure (DBP).3,5,8,11
The results in this study are in agreement with the
above studies, suggesting a strong positive association
between BMI and IOP in diabetics. In the nondiabetics
the correlation was not so significant. This suggests that
BMI has an additive effect on the raised IOP along with
hyperglycemia in diabetic subjects.
Sheila Pai, et al.
The basis for the elevated IOP among persons with
high BMI in diabetics is less certain. Several mechanisms
could underlie an effect of overweight on IOP. Mechanically, it has been suggested that intraorbital pressure due
to excess fat may cause an increase in episcleral venous
pressure and a consequent decrease in outflow facility10.
Both increased insulin secretion and insulin resistance result from obesity. Sang Woo Oh et al20 suggest
that insulin resistance might contribute to the association between IOP and obesity. High glucose levels in
the aqueous humor of diabetics may trigger excess
fibronectin synthesis, leading to excessive accumulation
of this in the trabecular meshwork and contribute to development of higher IOP in diabetics by increasing outflow resistance21,22.
Obesity increases blood viscosity through increasing red cell count, hemoglobin and hematocrit and consequently increased outflow resistance of episcleral veins
results. Further, obesity is also a risk factor for hypertension. Elevated BP increases IOP by increasing ciliary
artery pressure and ultrafiltration of aqueous humor.
Because corticosteroid secretion is increased in
obese persons, this may also explain this relationship10.
So, by various combined effects, obesity increases resistance in outflow facility, which, in turn, may contribute
to the development of increased IOP in the diabetics.
The study showed a significantly higher IOP in diabetics than the nondiabetics. The data showed an increase in IOP with increasing BMI and there was a positive correlation between this variable and IOP in diabetics. It indicates that the increase in BMI appears to be a
positive additive determinant of raised IOP in diabetics.
Because BMI correlates with raised IOP in diabetics and
it also predicts the future increase in IOP independently
from the baseline IOP, excess weight is undoubtedly is
one of the most important risk factors for elevated IOP
in diabetics. Weight control is the most natural primary
intervention method in the inter-relation of obesity, diabetes and elevated IOP and in the prevention of subsequent development of POAG in diabetics.
REFERENCES
1. Mitchell P, Smith W, Chey T, et al. Open-angle glaucoma and
diabetes: the Blue Mountains eye study, Australia. Ophthalmology 1997; 104(4):712-8.
77
Vol. 21 No. 2 Oct. 2008-Mar. 2009
TJPS
2. Klein BEK, Klein R, Moss SE. Intraocular pressure in diabetic
persons. Ophthalmology 1984; 91:1356-60.
3. M Cristina Leske, Suh-Yuh Wu, Anselm Hennis, et al. Risk Factors for Incident Open-angle Glaucoma The Barbados Eye Studies. Ophthalmology 2007; 13:1762-3.
4. Tielsch JM, Katz J, Quigley HA, et al. Diabetes, intra-ocular pressure, and primary open-angle glaucoma in the Baltimore eye survey. Ophthalmology 1995; 102:48-53.
5. L. M. Weih, B. N. Mukesh, C. A. McCarty, et al. Taylor. Association of Demographic, Familial, Medical, and Ocular Factors With
Intraocular Pressure Arch Ophthalmol 2001; 119(6):875-80.
6. Shiose Y. The aging effect on intraocular pressure in an apparently normal population. Arch Ophthalmol 1984; 102:883-7.
7. Shiose Y, Kawase Y. A new approach to stratified normal intraocular pressure in a general population. Am J Ophthalmol 1986;
101:714-21.
8. Klein BEK, Klein R, Linton KL. Intraocular pressure in an American community: The Beaver Dam Eye Study. Invest Ophthalmol
Vis Sci 1992; 33:2224-8.
9. Wu SY, Leske MC. Associations with intraocular pressure in the
Barbados Eye Study. Arch Ophthalmol 1997; 115:1572-6.
10. K. Mori, F. Ando, H. Nomura, et al. Shimokata.Relationship between intraocular pressure and obesity in Japan. Int J Epidemiol
2000; 29(4):661-6.
11. Lee JS, Lee SH, Oum BS, et al. Relationship between intraocular
pressure and systemic health parameters in a Korean population.
Clin Experiment Ophthalmol 2002; 30:237-41.
12. Armstrong JR, Daily RK, Dobson HL, et al. The incidence of
glaucoma in diabetes mellitus. A comparison with the incidence
of glaucoma in the general population. Am J Ophthalmol 1960;
50:55-63.
13. Bouzas AG, Gragoudas ES, Balodimos MC, et al. Intraocular
14.
15.
16.
17.
18.
19.
20.
pressure in diabetes. Relationship to retinopathy and blood glucose level. Arch Ophthalmol 1971; 85:423-7.
Bankes JLK. Ocular tension and diabetes mellitus. Br J
Ophthalmol 1967; 51:557-61.
Waite JH, Beetham WP. Visual mechanisms in diabetes mellitus;
a comparative study of 2002 diabetics, and 457 non diabetics for
control. N Engl J Med 1935; 212:367-429.
Palomar-Palomar A. Manifestaciones oftalmologicas de la diabetes mellitus. Arch Soc Oftalmol Hispano-Am 1956; 16:827-1067.
Armaly MF, Baloglou JP. Diabetes mellitus and the eye. II Intraocular pressure and aqueous outflow facility. Arch Ophthalmol
1967; 77:493-502.
Becker B. Diabetes mellitus and primary angle glaucoma. The
XXVII Edward Jackson Memorial Lecture. Am J ophthalmol
1971; 71:1-16.
Bulpitt CJ, Hodes C, Everitt MG. Intraocular pressure and systemic blood pressure in the elderly. Br J Ophthalmol 1975;
59:717-20.
Sang Woo Oh, Sangyeoup Lee, Cheolyoung Park, et al. Elevated
intraocular pressure is associated with insulin resistance and metabolic syndrome. Diabetes/Metabolism Research and Reviews
2005; 21(5):434-40.
21. Dielemans I, de Jong PT, Stolk R, et al. Primary open-angle glaucoma, intraocular pressure, and diabetes mellitus in the general
elderly population. The Rotterdam Study. Ophthalmology 1996;
103(8):1271-5.
22. An-Fei Li, Nobuhiro Tane, Sayon Roy, Fibronectin overexpression
inhibits trabecular meshwork cell monolayer permeability. Molecular Vision 2004; 10:750-7.
22. Toshiyuki, Naoya Fujimoto, Katsuhiro H, et al. Effect of chronic
hyperglycemia on intraocular pressure in patients with diabetes.
Am J Ophthamol 2007; 144(2):339.
78