Question 2:

Consider each of the following scenarios and state whether the variable in question is a confounder:

a.A study of the relationship between contact lens use and the risk of eye ulcers. The crude relative risk is 3.0, and the age-adjusted relative risk is 1.5. Is age a confounder in this study?

b.A case-control study of the relationship between cigarette smoking and pancreatic cancer. In this study, coffee drinking is associated with smoking and is a risk factor for pancreatic cancer among both smokers and nonsmokers. Assume that coffee drinking is not on the causal pathway between smoking and pancreatic cancer. Is coffee drinking a confounder in this study?

c. A study of the relationship between exercise and heart attacks that is conducted among men who do not smoke. Is gender a confounder in this study?

d.A cohort study of the risk of liver cirrhosis among female alcoholics. Incidence rates of cirrhosis among alcoholic women are compared to those among nonalcoholic women. Nonalcoholics are individually matched to alcoholics on month and year of birth. Is age a confounder in this study?