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Friday, July 18, 2014

Stroke Incidence and Mortality Rates Declining in the US, Study Finds

by Olga Rukovets

New research published in the Journal of the American Medical Association (JAMA) offers some good news for members of the stroke community: Stroke incidence and mortality rates in the US have decreased in recent decades (from 1987 to 2011), according to the July 16 paper by Silvia Koton, PhD, of the Stanley Steyer School of Health Professions at Tel Aviv University, and colleagues. However, the reported decreases in incidence and mortality rates were attributed to two distinct age groups.


The prospective cohort analysis included more than 14,300 participants (about 282,100 person-years) from four different US communities who were enrolled in the Atherosclerosis Risk in Communities (ARIC) study and free of stroke at baseline. Using interviews and physical examinations, the participants were recruited between 1987 and 1989; follow-up continued until 2011 with examinations, annual phone interviews, hospital discharge reports, and linkage with the National Death Index. All possible strokes were identified and classified them as definite or probable ischemic or hemorrhagic events by physician reviewers.


Dr. Koton and investigators identified 1,051 participants with incident stroke (7 percent): 929 had incident ischemic stroke, 140 had incident hemorrhagic stroke, and 18 participants had both during the study period. The stroke incidence rates were about 3.73 per 1000 person-years for total stroke: 3.29 per 1000 person-years for ischemic stroke, and 0.49 per 1000 person-years for hemorrhagic stroke, the researchers wrote.


Over time, the incidence of stroke decreased significantly in both white and black participants of both sexes (age-adjusted incidence rate ratio per 10-year period: 0.76, or an absolute decrease of 0.93 per 1000 person-years overall). However, the decrease in incidence was only evident in participants over the age of 65 (with an age-adjusted incidence rate ratio per 10-year period of 0.69, or absolute decrease of 1.35 per 1000 person-years), they said.


Mortality after stroke also decreased over time (HR, 0.80, or an absolute decrease of 8.09 per 100 strokes after 10 years). This decrease, on the other hand, was explained by the significant drop in mortality only among younger stroke patients (less than 65 years of age): HR, 0.65, the authors said.

Overall, Dr. Koton and colleagues found that stroke incidence and mortality rates decreased significantly from 1987 to 2011 in both men and women among white and black participants, due to a combination of different decreases in stroke incidence and mortality across age.


See our collection of stories on stroke research here: