Body mass index and stroke: overweight and obesity less often associated with stroke recurrence

Although obesity is associated with excess mortality and morbidity, mortality is lower in obese than in normal weight stroke patients (the obesity paradox). Studies now indicate that obesity is not associated with increased risk of recurrent stroke in the years after first stroke. We studied the association between body mass index (BMI) and stroke patient's risk of having a history of previous stroke (recurrent stroke).

A registry designed to collect data on all hospitalized stroke patients in Denmark 2000-2010 includes 61,872 acute stroke patients with information on BMI in 38,506. Data include age, sex, civil status, stroke severity (Scandinavian Stroke Scale), computed tomography, and cardiovascular risk factors. There were 28,382 patients with complete covariate information. We used multiple logistic regression models on this data set to compare the risk of stroke being recurrent in the 4 BMI groups: underweight (BMI<18.5), normal weight (BMI 18.5-24.9), overweight (BMI 25.0-29.9), and obese (BMI≥30.0).

Of the patients with complete covariate information, 22,811 (80.1%) had first-ever stroke; in 5571 patients (19.6%), stroke was recurrent. Multiple logistic regression analysis adjusting for age, stroke severity, sex, BMI, civil status, and cardiovascular risk factors showed that being obese and overweight in comparison with normal weight was associated with a significantly lower risk of stroke being recurrent (obese: odds ratio [OR]=.90, confidence interval [CI] .82-.98; overweight: OR=.89, CI .83-.96). Being underweight was associated with a significantly higher risk of stroke being recurrent (OR=1.23; CI 1.06-1.43).

The obesity paradox in stroke can be extended to include also stroke recurrence. Obese and overweight stroke patients had experienced less previous strokes than normal weight stroke patients.