From the descriptions provided, identify the type of study design that is being
ID: 164956 • Letter: F
Question
From the descriptions provided, identify the type of study design that is being described and explain why. 1. A study that evaluates two treatments for breast cancer. Women with stage 1 breast cancer are randomized to receive either cryotherapy or traditional lumpectomy. Women are followed for 5 years to determine if there are any differences in breast cancer recurrence and survival. (2 points) 2. A study that evaluates the relationship between breast cancer and a woman’s history of breastfeeding. The investigator selects women with breast cancer and an age-matched sample of women who live in the same neighborhoods as the women with breast cancer. Study subjects are then interviewed to determine if they breastfed any of their children. (2 points) 3. Fifteen hundred adult men who worked for Lockheed Aircraft were initially examined in 1951 and were classified by diagnostic criteria for coronary artery disease. Every three years they have been reexamined for new cases of the disease; attack rates in different subgroups have been computed annually. (2 points) Cohort. 4. A random digit dialed survey conducted in the City of Long Beach, California, reported that a greater proportion of nonsmokers endorsed a ban on smoking in alcohol serving establishments than did smokers. (2 points) 5. A study that began in 2010 of the relationship between exposure to chest irradiation and subsequent risk of breast cancer. In the study, women who received radiation therapy for postpartum mastitis in the 1950s were compared to women who received nonradiation therapy. The women were followed for 60 years to determine the incidence rates of breast cancer in each group. (2 points)
Explanation / Answer
Answer:
1. Cohort study.
The relationship between the occurrence of breast cancers and subsequent survival are investigated in relatively small cohorts in cases with conflicting results.
2. Control study, because we start with people with the outcome and look backwards in time to see exposure.
3. Cohort study
Cohort studies have the following key features:
a) Retrospectively or prospectively the investigators identify a cohort of subject who initiall did not have the diease or outcome of interest
b) Groups being compared differ in their exposure status
c) Investigators measure and compare the incidence of disease (or some outcome) among different exposure groups
4. Case control study
Two groups of people are included in this type of study. On group termed as experimental group is exposed to the specific outcome or disease, other group are kept as control. This study allows groups exposed to single or multiple outcomes.
5. Retrospective Cohort
Both the exposure and outcomes have occured by the time of study. This type of investigations studies prior outcomes and not future ones.
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