What type of study design is described in the abstract? How did the authors defi
ID: 210167 • Letter: W
Question
What type of study design is described in the abstract?
How did the authors define the primary exposure? Be specific.
Was the relative risk higher in men or women?
Which Bradford-Hill criterion of causality was cited in the abstract?
Provide 1 limitation of the selected study design.
Objective only a few prospective studies have examined the relationship between the frequency of cigarette smoking and the incidence of diabetes mellitus. The purpose of this study was to determine whether greater frequency of cigarette smoking accelerated the development of diabetes mellitus, and whether quitting reversed the effect. Methods Data were collected in the Cancer Prevention Study I, a prospective cohort study conducted from 1959 through 1972 by the American Cancer Society where volunteers recruited more than one million acquaintances in 25 US states. From these over one million original participants, 275 190 men and 434 637 women aged >30 years were selected for the primary analysis using predetermined criteria. Results As smoking increased, the rate of diabetes increased for both men and women. Among those who smoked >2 packs per day at baseline, men had a 45% higher diabetes rate than men who had never smoked; the comparable increase for women was 74%. Quitting smoking reduced the rate of diabetes to that of non-smokers after 5 years in women and after 10 years in men. Conclusions A dose-response relationship seems likely between smoking and incidence of diabetes. Smokers who quit may derive substantial benefit from doing so. Confirmation of these observations is needed through additional epidemiological and biological research.Explanation / Answer
What type of study design is described in the abstract?
The study design described in the abstract is a prospective cohort study. In this type of study, the progression of the disease under the influence of certain factors are being studied in the cohorts (individuals with similarities). Generally, the study period is long-term and the outcome of the study reveals the factors affecting the rate of disease progression. In the given abstract, the greater frequency of cigarette smoking was compared with the increase in the development of diabetes mellitus for a very long period (13 years).
How did the authors define primary exposure? Be specific.
The primary exposure in this study defines the increased development of diabetes mellitus due to the increased frequency of cigarette smoking.
Was the relative risk higher in men or women?
The relative risk was higher in women. The rate of diabetes development was found to be 74% in those women who smoked more than 2 packs per day.
Which Bradford-Hill criterion of causality was cited in the abstract?
In abstract it is mentioned that "as smoking increased, the rate of diabetes increased for both men and women". This observation matches with the Bradford-Hill criterion dose-response relationship which states that an increase in exposure increases the risk.
Provide 1 limitation of the selected study design
The number of men selected for the study is lower than the women. Men were 275190 and the women were 434637. The number of women participants were double than the men. The result showed that women are more prone to diabetes and this could be due to the increase in the number of women participants as well. So, this is one of the major limitations of the selected study design.
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