In a closed cohort study that included 2000 males age 4059 y

In a closed cohort study that included 2,000 males age 40-59 years, 400 had initial serum cholesterol levels of less than 220 mg %, 900 had levels of 220-270 mg % and 700 had levels greater than 270 mg %. Among these three cholesterol classes: (1) less than 220; (2) 220-270; and (3) greater than 270, the number of new cases of coronary heart disease during the first year of follow-up were 3, 12, and 14 respectively.

A.What was the incidence of coronary heart disease within each of the three cholesterol classes? (Assume complete follow-up).

B. Using cholesterol class 1 (<220) as the reference or unexposed group, calculate the absolute excess risk (the risk difference) of coronary heart disease for people in cholesterol class 2 (220-270). Interpret your results.

Solution

A) <220mg%=0.0075, 220-270 mg%=0.0133 and >270 mg%=0.02