Question

1. A cohort study was undertaken to examine the association between high lipid level and coronary heart disease. Participants were classified as having either a high lipid level (exposed) or a low or normal lipid level (unexposed). Because age is associated with both lipid level and risk of heart disease, age was considered a potential confounder, and the age of each subject was recorded. The following data describes the study participants:

                              Developed CHD     No CHD
EXPOSED (High lipid level)
                  young                 20          3980
                    old                 200             5800

UNEXPOSED (Low or normal lipid level)
                  young               18                6982
                     old                    65          2935

perform a stratified analysis and calculate the appropriate stratum-specific ratio measures of association (one for young, one for old). What are they?

Hint: You will have to combine the two tables, young and old based on exposures so that you create the standard 2x2 table with exposed and nonexposed rows.

B.Do the data provide evidence of effect measure modification? Justify your answer

Answer 1

To measure the association between high lipid level and coronary heart disease we will have to calculate Relative risk ERR) RR for young & Incidence in exposed young Incidence in non-exposed young times highes, ist low or normal 20 = 1.11 18 implies, High ugh lipid lipid level young level young are are relatively " relatively loll gisk of coronary heart disease as compared to Tipid level young. Incidence in exposed old Incidence in non-exposed old RR for old = 200 = 3·07 Implies, High lipid level old are solatively 3.07 times higher risk of coronary heart disease as compared to low or normal lipid level old. Doveloped CHO NO CHO 9780 Exposed (High lipid level) 220 83 Non-Expose 9917 (low or Normal lipid level) RR = Inådenie ined exposed Incidence in Non-exposed. 220 = 2.65 83 Implies, High lipid level are relatively 2.65 times higher risk of coronary heart disease as compared to low or normal lipid level.

Yes, the data provide eridence of effect measure modification. As we can see that the relative risk ratio is greates in old thand in youngs. So, old have to be cautious for the lipid level as it increases the chances of coronary heart disease in them. & we can also conclude that lipid association with coronary heart disease increases with the advancement of age .| people ,