Early and late coronary deaths in the US Railroad study predicted by major coronary risk factors

BACKGROUND: The purpose of this study was to explore the duration of the association of major coronary risk factors measured on a single occasion with coronary heart disease (CHD) deaths during 40 years in a population sample of middle-aged men. DESIGN: Measurement of age, systolic blood pressure, serum total cholesterol, and cigarette smoking was made on a single occasion in 2376 cardiovascular disease free men, aged 40-59, belonging to the US Railroad cohort of the Seven Countries Study enrolled in the late 1950s. During 40 years of follow up 627 men died from typical CHD (sudden death coronary death or definite myocardial infarction). METHODS: Eight partitioned proportional hazards models were solved, one for each independent 5-year block of follow up, to predict the risk of CHD death. Eight 5-year partitioned hazard scores, derived from the coefficients, were cumulated for each risk factor. RESULTS: The resulting curves showed a regularly increasing time trend in risk for coronary deaths as a function of serum cholesterol, systolic blood pressure and cigarette smoking, for the first 30-35 years of follow up followed by a loss of predictive power thereafter. The curves fit straight lines, with large squared correlation coefficients ranging from 0.96 to 0.99. There was a relatively constant strength in the association of risk factors levels with events, which are predicted irrespective of the distance from risk factor measurements. CONCLUSIONS: Measurement of major coronary risk factors taken on a single occasion in middle-aged men maintained a regular and almost monotonic relationship with the subsequent occurrence of CHD deaths for at least 30-35 years of follow up.