A previous analysis of stroke prevalence rates in the United States from 1999 to 2004 revealed that women in their midlife years were more than twice as likely as men of similar age to report having had a stroke, said Amytis Towfighi, an assistant professor in the Department of Neurology at the Keck School of Medicine of USC.
To determine if this was a new phenomenon and to explore the potential contributions of vascular risk factors to stroke prevalence rates, researchers analyzed data from the National Health and Nutrition Surveys 1988-1994 (NHANES III) and 1999-2004.
Researchers found that while 1.79 percent of women ages 35 to 54 who participated in NHANES reported having stroke, only 0.63 percent of women the same ages who participated in the earlier survey (NHANES III) reported stroke.
The analysis compared medical history variables (including smoking, diabetes mellitus, heart attack, high blood pressure), medication usage and clinical markers among women in NHANES III and 1999-2004.
Clinical markers evaluated included waist circumference, body mass index (BMI), total cholesterol, low density lipoprotein cholesterol (LDL), also known as bad cholesterol, and blood pressure.
“We did not find significant differences in presence of conventional cardiovascular risk factors, such as blood pressure, total cholesterol, LDL, smoking, heart disease, high blood pressure or diabetes, when we compared the two groups,” said Towfighi, lead author of the study.
Instead, women in the more recent survey were more likely to be using medications to control blood pressure and cholesterol. In fact, 14.8 percent of women in NHANES 1999-2004 reported using medications to lower blood pressure, compared to 8.9 percent in the earlier survey. Nearly 4 percent of women in NHANES 1999-2004 used medications to lower cholesterol, versus 1.4 percent in NHANES III.
“Women in NHANES 1999-2004 were significantly more obese than women a decade prior, with an average BMI of 28.67 kg/m2 versus 27.11 kg/m2 the decade prior,” Towfighi said. Body mass index of 25.0 to 30.0 is considered overweight, while an index of 30.1 or more is considered obese.
“In addition, women in NHANES 1999-2004 had an average waist circumference of nearly 4 centimeters more than women in the earlier study,” Towfighi said. Women in NHANES 1999-2004 also had higher average glycated hemoglobin (an indicator of poor blood sugar control).
The researchers concluded that although key traditional risk factors, such as high blood pressure, may not be higher today than in the 1990s, obesity and blood sugar markers are on the increase.
“Abdominal obesity is a known predictor of stroke in women and may be a key factor in the midlife stroke surge in women,” Towfighi said. “This study highlights the need to intensify efforts in curbing the obesity epidemic in the United States.”
UCLA researchers Rita Engelhardt and Bruce Ovbiagele were co-authors of the study.