Cumulative incidence and risk factors of myocardial infarction during 20 years of follow-up: comparing two cohorts of middle-aged men born 30 years apart.

Objective: To study cumulative incidence and predictors of myocardial infarction (MI) in two random general population samples consisting of middle-aged Swedish men born 30 years apart.

Method: Results from the "Study of Men Born In 1913" and the "Study of Men Born In 1943", two longitudinal cohort studies performed in the same geographic area and using the same methodology were compared. Both cohorts were followed prospectively from 50 to 70 years of age. MI was defined as first myocardial infarction, fatal or non-fatal.

Results: Men born in 1943 had a 34% lower cumulative risk of first MI [HR 0.66 (0.50-0.88), p = 0.0051] during follow-up as compared to men born in 1913. Interaction analysis showed that hypertension had a significantly higher impact on risk of MI in cohort 1943 than in cohort 1913 [HR 2.33 (95% CI 1.41-3.83)] and [HR 1.10 (0.74-1.62)], p = 0.0009 respectively. The population attributable risk for hypertension was 2.5-fold higher in the cohort of men born in 1943 as compared to men born in 1913, and diabetes mellitus and sedentary lifestyle attributed more to MI risk in cohort 1943 than in cohort 1913. On the contrary, smoking and total cholesterol have less attributable risk to MI in cohort 1943 than in cohort 1913.

Conclusion: Despite declining incident MI and improved cardiovascular prevention in general, hypertension remains an increasingly important attributable risk factor to MI together with diabetes mellitus and sedentary lifestyle over time.