The incidence of stroke in the U.S. over the past 50 years has declined, although the severity of stroke has not, according to a study.

Stroke continues to be a major public health concern, with more than 750,000 new strokes occurring each year in the United States. It is the third leading cause of death behind heart disease and cancer and the leading neurologic cause of long-term disability, according to background information in the article. Prior estimates of long-term trends in the incidence and severity of stroke have varied. Determining trends could help guide health programs, public policy, and the allocation of research funding.

Raphael Carandang, M.D., of Boston University, and colleagues examined data from the Framingham Study (health study, with participants initially recruited in 1948) to determine long-term trends in the incidence, lifetime risk, severity, and 30-day risk of death from clinical stroke. This study included 9,152 Framingham Study original participants and offspring undergoing follow-up for up to 50 years over three consecutive time-periods (1950-1977, 1978-1989, and 1990-2004), with ascertainment of stroke risk factor data every 2 years and active surveillance for occurrence of stroke or death.

The researchers found that the age-adjusted annual incidence of clinical stroke and atherothrombotic brain infarctions (ABI) in participants age 55 to 94 years decreased over the 3 periods. The incidence of clinical stroke decreased significantly. Across the 3 periods, the lifetime risk of clinical stroke (by age 90 years) decreased from 19.5 percent to 14.5 percent in men age 65 years and from 18.0 percent to 16.1 percent in women. Age-adjusted stroke severity did not vary across periods; however, death within 30 days of stroke decreased significantly in men (from 23 percent to 14 percent) but not significantly in women (from 21 percent to 20 percent).

"The severity of stroke has not decreased and 30-day mortality has decreased significantly only in men, perhaps due to an older age at onset of stroke and more severe strokes in women. These sobering trends emphasize that while improved control of risk factors has lowered incidence of stroke, there is a need for greater primary prevention efforts to reduce the lifetime risk, severity, and 30-day mortality following stroke," the authors conclude.