The Impact of Body Mass Index on Mortality After Stroke

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Abstract
Little is known about the contribution of obesity to the higher mortality risk among stroke survivors. We assessed the independent association between body mass index (BMI) and mortality among stroke survivors. Cross-sectional and prospective data from a nationally representative survey of noninstitutionalized civilian U.S. population aged 25 or older (n=20 050) with a baseline history of stroke (n=644) followed up from survey participation (1988-1994) through mortality assessment in 2000. Relationships between BMI and mortality attributable to all causes or cardiovascular causes were examined after adjusting for established prognosticators after stroke. Stroke survivors were more likely to be overweight (BMI 25 to 29 kg/m2) or obese (BMI > or =30 kg/m2 than those without stroke (64.3% versus 53.2%, P=0.003). In multivariable analysis, overall risk for all-cause mortality increased per kg/m2 of higher BMI (P=0.030), but an interaction between age and BMI (P=0.009) revealed that the association of higher BMI with mortality risk was strongest in younger individuals and declined linearly with increasing age, such that in the elderly, overweightness and obesity had a protective effect. The results were similar for the cardiovascular mortality outcome. Higher BMI after stroke is associated with a greater risk of all-cause and cardiovascular death among younger individuals. Younger stroke survivors may especially benefit from more vigorous efforts to monitor and treat obesity.