Abstract
Background:
The Framingham coronary heart disease risk score (FRS) estimates 10-year risk of myocardial infarction (MI) and coronary heart disease (CHD) death and is used to risk stratify individuals for vascular disease primary prevention. Since the preventive approaches to CHD and stroke are similar, a composite outcome may be more appropriate, and estimating risk of cardiac events alone may underestimate risk. We compared 10-year risk of MI or CHD death to risk of stroke, MI, or CHD death among individuals free of vascular disease, focusing on those with intermediate calculated FRS risk (10-20% over 10 years). We also used the Framingham general cardiovascular disease score (FGS), which calculates risk of a composite vascular outcome, but for which guidelines do not exist.
Methods:
The Northern Manhattan Study contains a prospective, population-based study of stroke- and CHD-free individuals ≥40 years of age, followed for a median of 10 years for MI, CHD death, and stroke. The FRS was used to calculate estimated 10-year risk of MI or CHD death. For those with intermediate estimated risk, Kaplan-Meier actual 10-year risks were calculated for 1) MI or CHD death and 2) stroke, MI, or CHD death. The cumulative risk of MI or CHD death was subtracted from risk of stroke, MI, or CHD death, and bootstrap methods produced 95% confidence intervals (CI) for the difference. This analysis was repeated using the FGS to stratify risk.
Results:
Among 2613 participants (53% Hispanic, 25% non Hispanic Black and 20% non Hispanic White), 867 had 10-20% estimated 10-year FRS risk. The actual 10-year risk of MI or CHD death was 14.2%. When stroke was added to the outcome, actual risk was 21.98% (absolute risk difference 7.78, 95% CI 5.86-9.75). For those with intermediate FGS risk, actual 10-year risk of MI or CHD death was 6.5. When stroke was added, actual risk was 10.55 (absolute difference 4.05, 95% CI 2.63-5.85).
Discussion:
In this multi-ethnic urban population, adding stroke to the risk stratification outcome cluster resulted in a 55% increase in risk and crossing of the threshold (>20% over 10 years) considered for preventive treatments such as statins. Research is needed to clarify the optimal use of primary risk stratification schemes, particularly among minority populations.