Stroke Risk Equally High in Men and Women Who Smoke

Megan Brooks

September 17, 2013

Cigarette smoking confers a similar risk for stroke in men and women, although women may be at greater risk for hemorrhagic stroke, a meta-analytic review of relevant research suggests.

The researchers admit the lack of any clear evidence of a sex difference in stroke risk related to smoking is "intriguing" given the strong evidence that smoking confers a greater excess risk for coronary heart disease in women compared with men.

"Importantly," they say, the analysis shows that both sexes benefit equally from kicking the habit.

"Cigarette smoking is a major risk factor for stroke for both men and women, but fortunately, quitting smoking is a highly effective way to lower your stroke risk," Rachel Huxley, DPhil, from the University of Minnesota in Minneapolis, said in a statement. "Tobacco control policies should be a mainstay of primary stroke prevention programs."

The meta-analysis was published online August 22 and will appear in the October issue of Stroke.

Major Independent Risk Factor Confirmed

The research team, from Australia, the Netherlands, and the United States, analyzed data from 81 prospective cohort studies that included nearly 4 million individuals and more than 42,000 strokes. Fifty-four cohorts came from Asia (31% of individuals), 12 from the United States (62%), 6 from Europe (4%), and 9 from Australia or New Zealand (3%).

Overall, the analysis "confirmed the importance of cigarette smoking as a major and independent risk factor for stroke and its major subtypes in all individuals," the researchers write.

Compared with nonsmoking, current smoking was associated with 83% (95% confidence interval [CI], 1.58 - 2.12) increased risk in women and 67% (95% CI, 1.49 - 1.88) increased risk in men. The pooled adjusted relative risk ratio (RRR) indicated a similar risk for stroke associated with smoking in men and women (RRR, 1.06; 95% CI, 0.99 - 1.13).

A regional analysis provided "some evidence" of a more harmful effect of smoking in women than in men in western (RRR, 1.10; 95% CI, 1.02 - 1.18) but not in Asian (RRR, 0.97; 95% CI, 0.87 - 1.09) populations.

There was also some evidence that smoking confers a greater risk for hemorrhagic stroke in women than in men (RRR, 1.17; 95% CI, 1.02 - 1.34; P .02). The researchers say it's possible that these findings are an artifact of the data because of the large number of comparisons performed, but they are "unable to preclude the possibility of a sex difference for this major stroke subtype entirely."

Compared with people who had never smoked, the benefits of quitting smoking on stroke risk were similar between the sexes (RRR, 1.10; 95% CI, 0.99 - 1.22).

Dr. Huxley and colleagues say their meta-analysis "provides the largest and most diverse prospective evaluation of the sex differential effects of smoking on risk of stroke."

Limitations of the analysis include the lack of standardization in study design and duration, end point definition (all strokes or fatal only), study populations, classification of the reference group of smoking, and amount of adjustment for confounders within studies.

It's estimated that more than 5 million people worldwide die each year because of smoking or other forms of tobacco use. Cigarette smoking accounts for 6.3% of the global burden of disease.

"It's importance as a major cause of ill-health is likely to continue for decades to come because smoking rates in low- and middle-income countries (where the majority of the population lives) continue to rise unimpeded," Dr. Huxley and colleagues write.

The study was funded by the Niels Stensen Fellowship. The authors have disclosed no relevant financial relationships.

Stroke. Published online August 22, 2013. Abstract

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