Midlife Strokes More Common Among Women

LOS ANGELES, June 21 -- Strokes in middle age strike women more than twice as often as they do men, researchers found.

Stroke prevalence was 2.39-fold higher for women than men at ages 45 to 54 (2.5% versus 1.0%, P=0.004), Amytis Towfighi, M.D., of the University of California at Los Angeles, and colleagues, reported online in Neurology.

In their analysis of the 1999 to 2004 National Health and Nutrition Survey (NHANES), modifiable risk factors, including heart disease and waist circumference appeared to be factors in the gender difference.

Because women are known to receive less preventive and diagnostic cardiovascular care than men, the findings reaffirm the need for improved risk factor modification among women, the researchers suggested.

"Prompt and close attention may need to be paid to the cardiovascular health of women in their mid-30s to mid-50s with a goal of mitigating this burden," they wrote.

The researchers analyzed data from a nationally representative sample of 17,061 adults in NHANES. Among the participants, 606 (4%) reported during the household interview that a physician had ever told them that they had experienced a stroke. About half were women (49%).

Respondents were not asked about transient ischemic attacks or stroke type.

The stroke rate was consistently higher among women than men in middle age, though the difference was only significant for the age range 45 to 54. The findings were:

• Similar rates between women and men at age 35 to 44 (1.2% versus 1.0%, OR 1.2142, 95% confidence interval 0.4715 to 3.1268, P=0.6876).
• Significantly higher rates among women than men at age 45 to 54 (2.5% versus 1.0%, OR 2.3903, 95% CI 1.3205 to 4.3267, P=0.0040).
• Similar rates between genders at age 55 to 64 (3.4% versus 3.0%, OR 1.1256, 95% CI 0.6218 to 2.0376, P=0.6961).

The increasing stroke rate with age-"a well-established predictor of higher stroke risk"-for both genders was not surprising, the researchers said.

Women in the 45 to 54 and 55 to 64 age groups were more likely to experience stroke than those in the 35 to 44 group (OR 2.1346, P=0.0667, and OR 2.9818, P=0.0078, respectively).

Men in the 55 to 64 age group were significantly more likely to have a stroke than those 35 to 44 (OR 3.2165, P=0.0034) or those 45 to 54 (OR 2.9665, P=0.0011).

There were also significant gender differences in the factors that contributed to stroke risk in a multivariate analysis that adjusted for race, ethnicity, waist circumference, systolic blood pressure, homocysteine, glycohemoglobin, total cholesterol, and history of hypertension, diabetes, smoking, and coronary artery disease.

For men ages 45 to 54, a history of smoking was the only independent predictor of stroke. For women, the only independent predictors were coronary artery disease (OR 12.79, P=0.0088) and waist circumference (OR 1.543, P=0.0489) after further adjustment for any use of hormone replacement therapy, which was not a significant predictor of stroke in the 45 to 54 age group.

In a separate multivariate analysis for severe headache or migraine (reported for the three months prior to the survey), this measure was an independent predictor of stroke as well among women (OR 4.859, 95% CI 1.864 to 12.669, P=0.0012).

"This sex difference in stroke predictors may not be surprising because we observed a steeper rise in several conventional vascular biomarkers over the course of midlife in women compared with men, with the biggest changes frequently occurring between 45 and 54 years," Dr. Towfighi and colleagues noted.

Blood pressure increased seven to 10 points per decade among women but four to five points with each decade among men. At age 35 to 54, the average systolic blood pressure was significantly higher among men (119.9254 versus 113.9440 mm Hg, P<0.0001). But by age 55 to 64, the opposite was true (128.6503 versus 131.9976 mm Hg, P=0.0082).

Total cholesterol levels followed the same pattern-increasing by 10 to 12 points each decade among women but remaining stable among men. Men had significantly higher levels at age 35 to 54, (208.6748 versus 197.5985 mg/dL, P<0.0001) but were overtaken by women by age 55 to 56 (208.6748 versus 197.5985 mg/dL, P<0.0001).

Likewise, homocysteine, glycohemoglobin, and triglyceride levels and the atherosclerosis biomarker ankle-brachial pulsatility index increased faster with age among women than men in midlife.

The investigators noted that these trends are in keeping with stroke trends seen over time in observational studies in the United States.

In the one study using the Swedish Hospital Discharge Register, women ages 30 to 65 had a 33% rise in strokes in 1998 to 2000 compared with 1989 to 1991, whereas men had only a 19% increase. Notably, most of the increases in this study were seen in patients younger than 60.

Dr. Towfighi and colleagues cautioned that the study's cross-sectional design "may limit any strong inferences from being drawn at this time" as to the reasons for the gender disparities in midlife stroke. Further study is needed, they said.

"In the meantime, our study suggests a substantial toll of stroke among women aged 45 to 54 years that may be amenable to optimal control of modifiable vascular risk factors," they concluded.