Decline in Stroke Rates Limited to Men

Nancy A. Melville

August 10, 2017

Recent encouraging declines in the overall incidence of stroke appear to be primarily driven by decreases in ischemic stroke rates among men but not women, new research suggests.

"By 2010, the rates of stroke were similar between women and men, which is different from almost all previous data showing that the rates of stroke are typically higher in men, especially after taking age into account," senior author, Tracy Madsen, MD, of the Alpert Medical School of Brown University in Providence, Rhode Island, told Medscape Medical News.

Using data from the Greater Cincinnati/Northern Kentucky Stroke Study, a population-based, biracial study including 1.3 million residents in southwest Ohio and northern Kentucky, Dr Madsen and her colleagues looked at all incident strokes among individuals aged 20 years or older between July 1993 and June 1994, and at subsequent time points of 1999, 2005, and 2010.

The results, published online August 9 in Neurology, showed that across the four time points, there were 7710 first-time strokes, of which 57.2% involved women.

While men showed a significant decline in the incidence of all strokes — from a mean of 263 per 100,000 at the beginning of the study to 192 per 100,000 at the end (P < .001) — the change over the same period in women was from 217 to 198 per 100,000, which was not statistically significant (P = .15).

Similar differences were observed in looking at ischemic stroke (per 100,000; men, 238 to 165 [P < .01]; women, 193 to 173 [P = .09]).

By 2010, the incidence of all and ischemic strokes did not differ between men and women.

"Data in recent years have shown a decrease in mortality from stroke, thought to be largely due to decreasing stroke incidence over time," the authors report.

"Our study findings, however, show that the overall decrease in stroke incidence over time is primarily driven by a decrease in ischemic stroke in men."

Rates of intracerebral and subarachnoid hemorrhages were stable over time in both sexes.

Despite the reduced rate of stroke in men compared with women, the study shows that both sexes had similar increases in rates of risk factors, such as hypertension or diabetes.

Dr Madsen noted, however, that there are important known sex differences in how those risk factors are manifested.

"Though we cannot be sure why stroke rates in women did not decrease significantly over this time period, one possibility is that stroke risk factors like diabetes, obesity, high cholesterol, and high blood pressure may be more severe or less well controlled in women compared with men," she explained.

"It is also possible that the biologic pathways by which risk factors like high blood pressure and diabetes lead to strokes differ in women compared with men, making standard prevention strategies less effective in women."

Notably, fewer women than men overall reported the use of aspirin for stroke prevention, which the authors noted was "a potentially concerning finding given knowledge that aspirin is recommended for women (but not men) 55–79 years old for primary prevention of ischemic stroke."

The mean age at the time of stroke significantly decreased in both groups over the course of the study, with women consistently older than men at each time point (overall mean age, 71.6 vs 67.3; P < .001), and there were greater decreases in functional independence, defined as a baseline modified Rankin Scale (mRS) score of 0 or 1, among women than men over time.

"If mRS is considered a surrogate for other measures of health including comorbidities or frailty, our data may indicate that our study population in 2010, especially women, were in worse health and at higher risk for stroke than in other study periods," the authors explained.

They note that the findings are consistent with recent data from the Centers for Disease Control and Prevention, which showed that stroke declined to the fifth leading cause of death for men but remained as the fourth leading cause of death for women.

In terms of case fatality, however, defined as death from any cause within 30 days of the incident stroke, the new study showed no significant difference by sex and few significant changes over time in stroke case fatality for women or men.

Limitations of the study include the higher stroke rates, in general, in the Kentucky-Ohio region, Dr Madsen noted.

"Though the population studied is representative of the greater United States with regards to race, gender, and socioeconomic status, it is important to note that the study population is part of the Stroke Belt, an area of the country with stroke mortality rates that are higher than the national average," she said.

"Future studies should evaluate whether stroke rates are decreasing over time in women living in other areas of the country."

The findings nevertheless underscore the need for stepped-up awareness of potential greater risk for stroke in women, Dr Madsen added.

"The main clinical implication of this study is that stroke prevention strategies may not be as effective in women compared with men; for example, future research should investigate the possibility that stroke risk factors like elevated blood pressure, cholesterol, and diabetes are more severe or are not as well controlled in women."

Increased Awareness

The authors of an accompanying editorial note important limitations, including the inability to assess such factors as chronic kidney disease or women-specific risk factors, such as hormonal or pregnancy complications.

They note that the study nevertheless underscores the need to increase awareness of the roles of sex in stroke risk.

"Since stroke occurs mostly in older people, the burden of stroke will most likely increase with the continuing aging of populations," conclude the authors, Silvia Koton, MD, from the Stanley Steyer School of Health Professions, Tel Aviv University, Israel, and Kathryn M. Rexrode, MD, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts.

"It is still speculative whether women will overtake men in having higher incidence rates of stroke, but if the trends reported [in the current study] continue, they might."

The study received support from the National Institute of Neurological Disorders and Stroke. The authors and editorialists have disclosed no relevant financial relationships.

Neurology. Published August 9, 2017. Abstract, Editorial

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