The incidence of stroke has declined significantly since 1987 in both blacks and whites and in both men and women, according to a prospective cohort study of residents in four U.S. communities.
Several studies have documented a decline in stroke rates in many other countries over the past decade, but there have been persistent racial, ethnic, and gender disparities in stroke rates in the United States, according to Silvia Koton, Ph.D., of Johns Hopkins University School of Public Health, Baltimore, and Tel Aviv University.
The report was published online July 15 in JAMA.
To assess long-term temporal trends, Dr. Koton and her associates analyzed data from the Atherosclerosis Risk in Communities (ARIC) study, a prospective cohort study of nearly 16,000 residents who were aged 45-64 years at baseline in 1987-1989 in Minneapolis; Washington County, Md.; Forsyth County, N.C.; and Jackson, Miss. ARIC included a comparatively large sample of black participants, and more than half the study subjects were women.
The researchers assessed 14,357 ARIC participants with 282,097 person-years. A total of 1,051 (7%) had a stroke during a median follow-up of 22.5 years for a incidence rate ratio of 3.73 per 1,000 person-years. Over time, the incidence of stroke showed an absolute decrease of 1.16 per 1,000 person-years after adjustment for age, other demographic variables, and time-varying prevalence of risk factors.
The incidence of stroke declined in blacks and whites, as well as in men and women. The incidence was 2.96 per 1,000 person-years for whites and 6.02 for blacks, with absolute, age-adjusted reductions of 0.83 per 1,000 person-years and 1.75 per 1,000 person-years, respectively. However, the decrease occurred only in people aged 65 years and older; the incidence of stroke remained steady throughout the study period in younger adults, the investigators said (JAMA 2014;312:259-68).
The risk of stroke mortality significantly declined by 20% after adjustment for age, but the reduction shrank to a nonsignificant 10% after the researchers fully adjusted for age, sex, race, center (demographic variables), hypertension, diabetes, smoking, and cholesterol-lowering medication use. In contrast to the decrease in incidence, the decrease in mortality was observed primarily among patients younger than age 65.
Stroke incidence and mortality have declined across racial groups, but the disparity between blacks and whites still persists, Dr. Ralph L. Sacco and Dr. Chuanhui Dong of the department of neurology at the University of Miami wrote in an editorial (JAMA 2014;312:237-8).
"Unless health disparities are addressed and innovative strategies to change behavior are developed and adopted, the cerebrovascular health of the population will be unlikely to improve." In particular, younger segments of the population must protect their brain health – especially by managing controllable risk factors such as diet, exercise, smoking, and obesity – to enhance the chance of successful cognitive aging, they noted.
The study was not designed to determine why these trends occurred, but it is likely that these factors played a significant role: improvements in the control of risk factors such as hypertension, smoking, diabetes, dyslipidemia, and atrial fibrillation, and the use of reperfusion therapy and improved postacute management strategies, the researchers said.
This study was supported by the National Heart, Lung, and Blood Institute and the National Institutes of Health. Dr. Koton and her associates reported no financial conflicts of interest. Dr. Sacco and Dr. Dong had nothing to disclose.