For each of the brief study descriptions presented below, first identify the out

Question

For each of the brief study descriptions presented below, first identify the outcome and the exposure then identify whether the study is descriptive or analytic. If the study is descriptive give the study type (case report or series, or cross sectional). If the study is analytic tell whether it is experimental or observational and, if observational, its type (cohort, case-control).

A. Fifteen hundred adult males working for Lockheed Aircraft are recruited to participate in a study of heart disease. Every 3 years they are examined for new occurrences of this disease. Heart disease rates are compared among groups defined by personal characteristics as they were recorded at the beginning of the study.

B. One hundred persons with infectious hepatitis and 100 healthy neighbors were questioned regarding their history of eating raw clams or oysters within the preceding 3 months.

C. Questionnaires were mailed to every tenth person listed in the city telephone directory. Each person was asked to list his or her age, sex, smoking habits, and respiratory symptoms during the preceding 7 days. Over 90% of the questionnaires were completed and returned. The prevalence of upper respiratory symptoms was determined from the responses.

D. During an outbreak of a severe neurological disease of unknown cause, the families of the patients suggest that the cause is adulterated cooking oil of a particular brand. What study design would be suitable? At what stage would you intervene if the accumulating evidence showed that the oil might be the cause?

E. Suggest a feasible study design that might be used to test the hypothesis that oral contraceptive use increases the risk of ovarian cancer in women.

These questions are from Epidemiology class.

Explanation / Answer

a) prospective cohort

b) case-control because control were people in same population

c) Cross-sectional or prevalence study; can estimate prevalence and prevalence odds ratio.

d) These studies are observational, because the role of the investigator is merely to observe what happens, noting who is exposed or unexposed and who has or has not developed the outcome of interest.

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