Context: Prior estimates of long-term trends in the incidence and severity of stroke have varied; trends in lifetime risk have not been reported.
Objective: To determine long-term trends in the incidence, lifetime risk, severity, and 30-day mortality of clinical stroke.
Design, setting, and participants: Prospective evaluation of the community-based Framingham Study original and offspring cohorts. Participants were 9152 men and women free of prevalent stroke and undergoing follow-up for up to 50 years over 3 consecutive periods (1950-1977, 1978-1989, and 1990-2004), with biennial ascertainment of stroke risk factor data and active surveillance for incident clinical stroke and cause-specific mortality.
Main outcome measures: Incidence (age-adjusted, sex-specific), severity, 30-day mortality, and mortality-adjusted 10-year and lifetime risk of stroke in each of the specified periods.
Results: There were 1030 incident clinical strokes (450 [44%] in men, 629 atherothrombotic brain infarctions [61%]) in 9152 persons 55 years or older over 174,917 person-years of follow-up. The age-adjusted incidence of first stroke per 1000 person-years in each of the 3 periods was 7.6, 6.2, and 5.3, respectively, in men (P = .02 for trend) and 6.2, 5.8, and 5.1 in women (P = .01 for trend). The lifetime risk at age 65 years decreased from 19.5% to 14.5% in men (P = .11) and from 18.0% to 16.1% in women (P = .61). Age-adjusted stroke severity did not vary across periods; however, 30-day mortality decreased significantly in men (from 23% to 14%; P = .01) but not significantly in women (from 21% to 20%; P = .32).
Conclusions: In this cohort of men and women free of prevalent clinical stroke at initial examination, incidence of stroke has decreased over the past 50 years but the lifetime risk has not declined to the same degree, perhaps due to improved life expectancy. The results of this study suggest that improved control of risk factors has lowered stroke incidence but emphasize the need for continued primary prevention efforts.