Diabetes and hypertension attenuated the relationship between obesity and stroke, suggesting that these factors may explain much of the risk.
The degree of obesity, as defined by BMI, waist circumference, or waist-to-hip ratio, is a significant risk factor for ischemic stroke, regardless of sex or race, according to a study in the January 21 online issue of Stroke. Thus, the prevention and control of obesity has the potential to reduce the incidence of stroke through its effect on known predictors of stroke, reported lead author Hiroshi Yatsuya, MD, PhD, visiting Associate Professor at the Division of Epidemiology and Community Health, School of Public Health, University of Minnesota, in Minneapolis, and colleagues.
The researchers obtained data regarding BMI, waist circumference, and waist-to-hip ratio from 13,549 black and white men and women (ages 45 to 65), who were enrolled in the Atherosclerosis Risk in Communities Study. No participants had cardiovascular disease or cancer at baseline. A total of 598 incident strokes occurred during a median follow-up of 16.9 years.
Race, Sex, Obesity, and Stroke
Crude incidence rates varied more than threefold by race and sex, from 1.2 per 1,000 person-years in white women to 4.3 in black women in the lowest BMI category and 2.2 in white women to 8.0 in black men in the highest BMI category. “The absolute difference in incidence rates for being in the highest BMI quintile compared with the lowest quintile ranged from 1.9 per 1,000 person-years in white women to 5.6 per 1,000 person-years in black women,” stated Dr. Yatsuya and coauthors.
Overall, blacks had about two to three times higher incidence rates of ischemic stroke than whites in each obesity quintile. “However, hazard ratios for the highest versus lowest quintile of BMI, waist circumference, and waist-to-hip ratio ranged from 1.43 to 3.19, indicating increased stroke risk associated with obesity, regardless of the measure, without statistical evidence for differences by race or sex,” stated Dr. Yatsuya’s group. Also, significant positive associations of obesity measures with ischemic stroke incidence were largely explained by mediators related to obesity among all race-sex groups.
From a public health point of view, they estimated population-attributable-fraction values and suggested that 18% to 20% of ischemic stroke occurrence may be accounted for by BMI greater than or equal to 28.1 kg/m2, waist circumference greater than or equal to 100 cm, or waist-to-hip ratio greater than or equal to 0.95.
Hypertension did not modify the relationship between obesity measures and the incidence of ischemic stroke. “In other words, in subjects both with and without hypertension, there were significant positive associations between obesity measures and ischemic stroke incidence,” commented Dr. Yatsuya and colleagues. “These associations were, however, significantly attenuated with additional adjustment for systolic blood pressure. Given the strong association between obesity and hypertension and other risk factors, including diabetes mellitus, obesity would be an important target for the prevention of ischemic stroke.”
—Colby Stong