2 - Week 3 Q-1. In a cohort study of the relationship between exogenous estrogen and the subsequent risk of breast cancer (BC), 1000 premenopausal women were followed for 10 years. 500 of these women took estrogen and 500 did not. At the end of the 10 years, 300 of those taking estrogen had developed BC compared with 100 of those who were not taking estrogen. 1. Calculate the average annual incidence of BC in the exposed and unexposed 2. What is the relative risk (RR) associated with taking estrogen in this study? 3. What is the risk difference (RD) for estrogen and BC? 4. What is the etiologic fraction (EF)? Convert this fraction into a percent (EF%) 5. For this total population of 1,000 women, what was the average annual incidence of BC (i.e. Ipopulation)? 6. What was the population risk difference (PRD) for BC in women taking estrogen in this population of women? 7. What was the population etiologic fraction (PEF) in this population? Convert the fraction to a percent (PEF%) 1 Q-2. At the start of a study of alcohol consumption and the risk of coronary heart disease (CHD), investigators recruited 10,000 people. At the first exam, 2000 of these were found to have CHD. Of the 8,000 without CHD, 3,000 were heavy consumers of alcohol (\"drinkers\") and 5,000 had low/no consumption of alcohol (\"non-drinkers\"). The investigators followed these 8,000 people for one year. During this year, 84 of the \"drinkers\" developed CHD and 90 of the \"non-drinkers\" developed CHD. (Please note that these are fictitious data!). Answer the following questions, using a base of 1,000. A. What was the prevalence of CHD in the group at baseline? B. To analyze the results of the cohort follow-up study, first draw and label a 2 x 2 table: C. Using the above data, calculate the following measures: 1. CHD incidence in the exposed (Ie) 2. CHD incidence in the unexposed (Iu); 3. The Risk Ratio (RR); 1) How would we verbalize the risk to drinkers compared to non-drinkers shown by this RR? 2) The RR is a measure of the strength of the association between exposure and outcome; do you think that an RR this size is a weak, moderate or strong evidence for the association between alcohol consumption and CHD? 4.The Risk Difference is: 5. The etiologic fraction % is: Interpret this RD Interpret this EF % 6. Using all 8,000 as the total population, calculate the incidence of CHD in this total population (Ip) 7. What is the population excess risk (PER) in this total population? 8. Calculate the population etiologic fraction %. 2 D. Suppose the investigators study the relationship between drinking and CHD in another population, also with a total of 8,000 people at risk. However, in this population, 7000 are heavy drinkers and only 1000 are not. Assume that the incidence in the exposed and in the unexposed is the same as in their first study. Calculate the PEF% for this second population; (and yes, there is enough information above to do this!) 3