NEW ORLEANS—The rate of stroke has tripled among middle-aged women in the United States in less than two decades. During this period, waist circumference and BMI have also increased in middle-aged women, said Amytis Towfighi, MD, at the 2008 International Stroke Conference. Although the waistlines of middle-aged men have been increasing as well, the incidence of stroke in this group has remained essentially the same.
Waist circumference is a component of metabolic syndrome, and as Dr. Towfighi suggested, the effect of metabolic syndrome on stroke risk is greater in women than in men. Previous research, using data from 1999 to 2004, found a stroke prevalence that was twice as high among women ages 45 to 54 compared with men of similar ages.
Obesity, Age, and Stroke
Dr. Towfighi, Assistant Professor of Clinical Neurology at the University of Southern California, Los Angeles, and colleagues sought to determine if this observed disparity in stroke prevalence was a reflection of an increasing stroke rate among middle-aged women or a decreasing rate among middle-aged men. If the midlife disparity was due to an increasing stroke prevalence among women, the investigators would measure trends over time in the prevalence of historical vascular risk factors, biomarkers, and medication use among women.
The researchers assessed midlife stroke prevalence with the use of two surveys, the National Health and Nutrition Examination Survey III (NHANES III; 1988 to 1994) and the NHANES IV (1999 to 2004), looking specifically at stroke prevalence, medical histories, and biomarkers among 35- to 54-year-old men and women. The study sample included individuals who answered the question “Have you ever been told by a doctor that you have had a stroke?” for the NHANES III (n = 5,112) and the NHANES IV (n = 4,594).
Among middle-aged women, stroke prevalence increased from 0.6% in NHANES III to 1.8% in NHANES IV, whereas it changed little among men of similar ages (0.9% in NHANES III and 1.0% in NHANES IV).
The percentage of middle-aged women with abdominal obesity, defined as a waist circumference exceeding 88 cm, increased from 47% to 59% during the two survey periods. Women in NHANES IV had an average waist circumference of nearly 4 cm more than those in the earlier study, explained Dr. Towfighi. Among middle-aged men, the prevalence of abdominal obesity increased from 29% to 41%.
Mean BMI increased in both genders across the surveys—from 27.1 to 28.7 among middle-aged women, and from 27.2 to 28.4 among middle-aged men.
Medical History, Biomarkers, and Medication Usage
Most levels of key biomarkers and traditional vascular risk conditions remained stable or actually improved among the women from the earlier to the later survey, possibly due to increased use of vascular risk–reduction pharmacotherapy, noted Dr. Towfighi. For example, levels of HDL cholesterol and homocysteine improved during this time. Among middle-aged women, use of antihypertensive medications increased from 8.9% in the earlier survey to 14.8% in the later survey, and the percentage of women taking drugs to treat dyslipidemia went up from 1.4% to 4.0%.
Glycemic markers and luteinizing hormone levels, however, increased significantly in women during the two survey periods. These markers are linked to obesity and support the untoward health effect of the growing obesity epidemic, said Dr. Towfighi.