Framingham stroke risk function in a large population-based cohort of elderly people: the 3C study.

BACKGROUND AND PURPOSE: External validation of the Framingham stroke risk function has been rarely performed. We assessed its predictive ability in a population-based cohort of French elderly. METHODS: The sample comprised 6913 subjects from the 3C Study, aged 65 to 84 at baseline, who were followed up to 6 years. Predictive accuracy of the original Framingham stroke risk function was assessed in a 3-step procedure: comparison between the Framingham and 3C cohorts of the prevalence of selected risk factors and the associated relative risks (RR) for stroke, comparison of the predicted to the observed number of stroke events (calibration), and ability to separate high-risk from low-risk participants (discrimination). We also compared predictive performances of the original Framingham, the recalibrated Framingham, and the local stroke risk functions. RESULTS: During follow-up, 110 incident strokes occurred. For most risk factors, RRs were comparable between the 2 cohorts, except for age in women. The original Framingham stroke risk function applied to the 3C cohort overestimated the 6-year absolute risk for stroke by a factor of 3.7 for men and 4.4 for women. However, the recalibrated Framingham and 3C functions did not show any over- or underestimation of stroke risk. The 3 stroke risk functions (original, recalibrated, and 3C) provided acceptable discrimination with areas under the ROC curve ranging from 0.67 to 0.73. CONCLUSIONS: The original Framingham stroke risk function strongly overestimated the stroke risk for 3C participants. Derived Framingham stroke score sheets should not be directly used by physicians in the French elderly population.