Women Face Surge in Stroke Risk at Midlife

Susan Jeffrey

June 21, 2007

June 21, 2007 — A new study using data from the National Health And Nutrition Examination Survey (NHANES) shows the risk for stroke among US women between the ages of 45 and 54 years is more than double that of men the same age.

Independent predictors of stroke risk in this age group included the presence of coronary artery disease and increased waist circumference, suggesting that poor risk-factor control in these women may be to blame for the increased risk.

"Women aged 45 to 54 had twice the odds of having experienced stroke compared with men of the same age, and the transition from age 35 to 44 to 45 to 54 marks the steepest rise in stroke prevalence for women," lead author Amytis Towfighi, MD, from the Stroke Center and department of neurology at the University of California, Los Angeles, told Medscape.

Their study also showed that from 1999 to 2004, stroke prevalence rates rose in women while they declined in men.

The results are published online June 20 in Neurology. Their findings were presented earlier this year at the American Stroke Association International Stroke Conference 2007 and reported by Medscape at that time.

Poor Risk-Factor Control?

Although the majority of strokes occur in older age groups, those in midlife, between the ages of 35 and 64 years, are still at risk, Dr. Towfighi pointed out. Women under the age of 65 years have risk factors particular to their gender, including risks associated with pregnancy, the use of oral contraceptives and hormone replacement therapy, and a higher prevalence of migraines.

"Understanding gender-specific differences in the frequency and predictors of stroke in midlife years is important, which is what prompted us to look into this," Dr. Towfighi said.

For this study, they used NHANES data from 1999 to 2004 on 17,061 men and women to look at sex differences in stroke prevalence and identify independent risk predictors among middle-aged individuals. Stroke was identified through the in-home interview portion of the survey, where subjects were asked if they had ever been told by a physician that they'd had a stroke.

Of the 17,061 men and women surveyed, 15,309 responded to the question about stroke (90%). Of these, 606, or 4%, reported having experienced a stroke, 51% of whom were men and 49% women.

Based on these data, they found that women between 45 and 54 years had significantly higher odds of having had a stroke compared with men of the same age group.

Stroke Risk Among Individuals 45 to 54 Years of Age: Women vs Men

End Point
Odds Ratio (95% CI)
P
Risk for stroke
2.39 (1.32 – 4.32)
.0040

No other significant differences in stroke risk were found for the other midlife age groups. A trend toward higher stroke risk was seen for women aged 45 to 54 vs those aged 35 to 44, but no difference was seen between that age group and those aged 55 to 64.

In terms of stroke trends between 1999 and 2004, the prevalence in men and women was similar in 1999 but increased significantly in women, while it decreased in men, Dr. Towfighi noted, "so that by 2004, women were more than 4 times as likely to have had a stroke than men."

Independent predictors of stroke risk in women aged 45 to 54 were the presence of coronary artery disease and increasing waist circumference.

Independent Predictors of Stroke Risk in Women Aged 45 to 54 Years
Factor
Odds Ratio (95% CI)
P
History of coronary artery disease
12.790 (1.901 – 86.063)
.009
Waist circumference (∆ = 15 cm)
1.543 (1.002 – 2.376)
.049

In addition, several vascular risk factors, including systolic blood pressure and total cholesterol levels, increased at higher rates for women vs men for each of the 3 midlife age groups between 35 and 64 years. For example, she noted, blood pressure increased by 8 to 10 mm Hg with each decade among women, whereas in men it increased only 4 to 5 mm Hg.

"Our thoughts are that the greater rise in vascular risk factors in women over their midlife years vs men could account for this increase in stroke prevalence," Dr. Towfighi noted. For example, waist circumference was an independent predictor of stroke in women, suggesting the current epidemic in obesity in the United States may be playing a role. "Both the general public and healthcare practitioners tend to underestimate women's cardiovascular risk and think of middle-aged men as being at higher risk," she added.

Dr. Towfighi pointed to some limitations of their study, including the fact that it was cross-sectional in design, was not able to distinguish the type of stroke, and relied on self-report of stroke. However, in terms of strengths, it used data from a nationally representative sample and had rigorous and standardized biomarker assessments for all parameters.

"Additional study is certainly needed, and calls for a nationwide, systematic mechanism for tracking the incidence of heart disease and stroke in the United States may help facilitate a prompt and more in-depth understanding of burgeoning public health issues like the one raised in this study," the authors conclude in their paper.

"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 risk factors. 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."

Neurology . 2007. Published online June 20, 2007.

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