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Incident stroke risk increases with rising BMI
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A meta-analysis of more than 4 million adults suggests there is a J-shaped association between BMI and risk for incident stroke, with each 5-unit BMI increment increasing stroke risk by 10%, according to findings published in Nutrition, Metabolism and Cardiovascular Diseases.
“Substantial evidence reported that adiposity, measured by BMI, is an independent risk factor for stroke; however, questions remain about the shape of the dose-response relation,” Dongsheng Hu, PhD, professor in the department of preventive medicine at Shenzhen University Health Sciences, Guangdong, China, and colleagues wrote in the study background. “Some studies suggested a linear association between BMI and stroke, but others suggested a J- or U-shaped relation. Although a meta-analysis of 25 cohort studies including 2 million participants reported an increased risk of ischemic stroke in overweight and obese people, this study did not investigate the dose-response association between BMI and stroke risk.”
Hu and colleagues analyzed data from 44 cohort studies published through May that assessed the relationship between BMI and stroke risk, including 102,466 incident cases of stroke among 4,432,475 participants. Studies were included if they reported risk estimates of stroke by at least three levels of BMI. Researchers used generalized least-squares regression to estimate study-specific dose-response coefficients from the natural logs of reported risk estimates across categories of BMI and calculated pooled relative risk vales for a 5-unit increment in BMI, also investigating the association between BMI and risk by stroke type (hemorrhagic and ischemic).
Across studies, 10 included men only, eight included women only and 13 presented sex-specific estimates. Mean duration of follow-up ranged from 3.4 to 44 years; mean baseline age ranged from 40 years to 72 years.
Researchers found that, for each 5-unit increment in BMI, summary relative risk was 1.1 (95% CI, 1.06-1.13), with a J-shaped dose-response relationship. There was no association between BMI and incident stroke in adults with a BMI of less than 24 kg/m²; however, risk increased steadily in those with a BMI of at least 25 kg/m², according to researchers.
When stratified by stroke subtype, summary RR for each 5-unit increment in BMI were 1.2 (95% CI, 1.15-1.26) and 0.99 (95% CI, 0.93-1.05) for ischemic and hemorrhagic stroke, respectively. In non-linear, dose-response analysis, researchers found evidence of non-linearity for ischemic stroke (P = .017 for non-linearity) with risk increasing with increasing BMI. However, in non-linear, dose-response analysis for hemorrhagic stroke, researchers observed a U-shaped relationship, with the lowest risk among those with a BMI of 24 kg/m² (P < .0001 for non-linearity). Results persisted in analyses stratified by sex, geographic location, duration of follow-up, number of cases, study quality and adjustment for confounders including age, smoking status, alcohol consumption and education.
The researchers noted that only BMI was evaluated in the analysis, which does not allow for assessing fat distribution, meaning the measurement may incorrectly estimate the association of stroke risk and adiposity in those with heavy muscle mass. – by Regina Schaffer
Disclosure: The authors report no relevant financial disclosures.
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