Download Case Study Week 5

Diana Pinney
Case Study Week 5
1. The first study is a case study because it was relatively small,
compromising around 20 hospitals. Also, the cases were chosen as
individuals that had been diagnosed with lung cancer and the controls
where chosen from patients occupying the hospital at the same time but
diagnosed with a different disease.
2. The second study is a cohort study because a population group (doctors
in England) was chosen to self-report on smoking habits via
questionnaire and this reporting was followed each physician who
smoked until they turned into a death certificate.
3. It is more feasible to perform a case control study on a population that is
fixed or has something in common, such as patients in hospital. Hospital
settings also provide quick access to subjects for interview or study,
which saves time and money.
4. Other sources of controls in the case control study could have been
nuclear family members of the lung cancer patient whom did not smoke.
5. The advantages of selecting controls from the same hospital as the cases
include efficiency and willingness to participate.
6. Lung cancer patients in the hospital are significantly representative of all
patients with lung cancer. It would not be a stretch to generalize that
hospitalized lung cancer patients are indicative of the exposure and future
that most people with lung cancer in this era would face.
7. People without lung cancer that are hospitalized are not very
representative of the general population without lung cancer. A majority
of the general population does not have lung cancer, while a majority of
the population is not hospitalized. Hospitalized people without lung
cancer to represent the general population because both are less likely to
be smokers.
8. There is an issue of external validity and representativeness between the
cases and control group because it is easy to seethe control group is much
more likely to not to be smokers. This glaring fact may influence bias.
9. Proportion smoked, cases: 1350/1357 or 99%
Proportion smoked, controls: 1296/1357 or 96%
10.I infer that the population of cases had 4% more smokers than the
population of controls.
11a. 99%
11b. 96%
12.The odds ratio = 9.6. The cases are 9.6 times more likely to be smokers
than the controls.
The cross product of the ratio is the relative risk, which is 5.2. The
smokers in the case population have more than 5 times more risk in
getting lung cancer than the controls.
13. I would infer than lung cancer is made 9.6 times more likely to occur in
smokers than non-smokers and that smokers have 5 times more risk of
getting lung cancer than non-smokers.
14.
Daily # of cigarettes
0
1-14
15-24
25+
All smokers
OR
x
7
9.5
16.3
9.6
15. All smoking holds a higher risk than not for lung cancer, but the more
cigarettes that are smoked per day, the higher the odds of developing lung
cancer are.
16. I would assume that someone that has the time to smoke 25+ cigarettes
in a day is failing in other areas of personal wellbeing. Perhaps heavy
smokers get less exercise and have an improper diet.
17. Even though this study’s questionnaire may have been anonymous, it
might not be easy for a physician (even in the name of health and science) to
fill out a survey admitting to being a smoker. Only 6,192 of the respondents
were female, which may be an accurate ratio of female physicians, but is not
an accurate ratio of females in the general population.
18.
# Cigs Daily
0
1-14
15-24
25+
All smokers
Total
MR/1,000 yrs.
0.07
0.6
1.4
2.2
1.3
0.9
RR
x
8.6
20
31.4
18.6
12.9
Rate difference
X
0.53
1.33
2.13
1.23
0.83
Mortality rate calculates the disease ratio. For example, 1.4 cases of lung
cancer will arise (in people who smoke 15-24 cigarettes per day) per 1,000
people per year.
Rate ratio calculates the risk that cases have of developing a disease per
exposure.
Rate difference calculates disease burden.
19. This is called a cause specific mortality rate. The proportion of lung
cancer deaths among all smokers that can be attributed to smoking is
133/136.
20. Assuming that every case of cancer in smokers was due to them
smoking, if no one had smoked, 133 deaths would have been prevented.
21. Death from cardiovascular disease has a stronger association with
smoking. The actual mortality rate and deaths due to cardiovascular disease
are higher than lung cancer. Risks associated with smoking and lung cancer
are higher than heart disease, but more actual deaths come from heart
disease.
22. PAR% Lung Cancer: 92%
PAR % Cardiovascular Disease: 17%
These 2 measures vary greatly, but are similar to the Attributable risk
percent.
23.
Lung Cancer: 1.3 deaths
Cardiovascular disease: 9.51 deaths
24. These data imply that the sooner one quits smoking, the less chance they
have of dying from lung cancer. It implies that the field of public health and
preventative medicine could benefit the population greatly by instating as
many tobacco cessation programs as possible.
25. It appears that the cohort study makes smoking seem the most
dangerous. This is a more accurate study design for this kind of query as it
has followed a cohort through time for a more accurate picture of an
exposure association.
26.
Case Control
Advantages
Sample size
Cost
Study time
Rare disease
Disease rates
Disadvantages
Multiple outcomes
Recall bias
Cohort
Advantages
Rare exposure
Progression, spectrum of illness
Multiple exposures
Disadvantages
Sample size
Cost
Study time
Selection bias
Loss to follow-up
27. I would have done a case control study first. Completing a quick and
cheap study could be a first step in finding an association with a disease and
exposure. A strong association could lead an investigator to completing a
longer and more accurate study such as the cohort study.
28.
Strong association: yes
Consistency among studies: yes
Exposure precedes disease: yes
Dose-response effect: yes
Biologic plausibility: yes