Question

Classify each of the following studies as:

A. Cohort

B. case-control

C. cross-sectional

____ 1. Representative sample of residents were telephoned and asked how much they exercise each week and whether they currently have (have ever been diagnosed with) heart disease.

____ 2. Occurrence of cancer was identified between April 1991 and July 2002 for 50,000 troops who served in the first Gulf War (ended April 1991) and 50,000 troops who served elsewhere during the same period.

____ 3. Persons diagnosed with new-onset Lyme disease were asked how often they walk through woods, use insect repellant, wear short sleeves and pants, etc. Twice as many patients without Lyme disease from the same physician's practice were asked the same questions, and the responses in the two groups were compared.

Answer 1

1) This study is a cross sectional study because it is showing present exposure and disease

2) This study is a cohort study because it is showing present exposure and future disease

3) This study is a case control study became is is showing present disease and past exposure