News Article
Central Adiposity Better Than BMI as Predictor of Cerebrovascular Events
Measures of abdominal adiposity appear to be better predictors of stroke or transient ischemic attack than does body mass index, based on a German study of more than 1,100 individuals.
"Three different statistical approaches uniformly showed that various markers of abdominal adiposity were superior to body mass index (BMI) in predicting risk of stroke or TIA [transient ischemic attack]. The waist-to-hip ratio served as the best predictor among the obesity markers," said Dr. Yaroslav Winter of the University of Heidelberg, Germany, in the study published online on Aug. 14 in the journal Stroke (Stroke 2008 Aug. 14 [doi:10.1161/strokeaha.108.523001).
The study involved 379 consecutive patients with ischemic stroke (301), intracerebral hemorrhage (37), or transient ischemic attacks (41), recruited from the neurology departments of two German academic facilities. Patients with a history of cerebrovascular events were not excluded. Each case patient was matched with two control subjects (758), who did not have a history of cerebrovascular disease. Each patient underwent a physical and neurologic examination, including CT or MRI of the head. Stroke was defined using World Health Organization criteria.
Control subjects were matched for age and sex from the European Investigation into Cancer and Nutrition (EPIC) Heidelberg study, which involved more than 25,000 participants. Subjects in this pool were aged between 45 and 75 years. Age groups (less than 50, 50-55, 56-60, 61-65, 66-70, and more than 70) were used for matching.
Obesity was characterized a number of ways: body mass index, waist-hip ratio (WHR), waist circumference, and waist-stature ratio (WSR). BMI was calculated as weight (kg) divided by height (m²). Waist circumference was measured in centimeters. WHR was defined as waist divided by hip circumference. WSR was defined as waist circumference divided by body height.
Men accounted for 63% of case and control groups. Controls were slightly younger on average - 65 vs. 67 years. The prevalence of obesity, defined by BMI, was significantly greater among cases (30%), compared with controls (20%) (
"The risk of stroke or TIA increased in a graded manner with increasing WHR," the researchers noted. Patients in the highest tertile for WHR (compared with the lowest tertile) had a more than sevenfold increased risk of stroke or TIA (odds ratio, 7.69;
Increased waist circumference was also associated with increased risk of stroke or TIA, with those in the highest tertile having a more than fourfold increased risk, compared with those in the lowest tertile (OR, 4.25;
When adjusted for age and sex only, BMI showed a positive association with risk of stroke or TIA, with an odds ratio of 2.34 (
The researchers also looked at the effect of a one-standard-deviation increase in the three obesity measures on stroke/TIA risk. "The increase in OR calculated for 1 SD increase in WHR was the largest among all anthropomorphic indices studied [and] the OR associated with 1 SD increase in BMI was the weakest one," they wrote.
Additionally, the researchers looked at the area under receiver operator curves for the different obesity measures. This provides a measure of the accuracy of a diagnostic test. Accordingly, WHR was a slightly better predictor of stroke/TIA than WSR. BMI was the worse predictor, with accuracy comparable to guessing.
"The redefinition of obesity based on the waist-to-hip ratio or waist circumference instead of BMI increases considerably the estimate of cerebrovascular events attributable to obesity," they wrote.
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