Obesity paradox and stroke outcomes according to stroke subtype: a propensity score-matched analysis

Objective Obesity has traditionally been considered a risk factor for ischemic stroke. However, some clinical observations have reported a complex relationship between patients who are overweight or obese with paradoxically better stroke outcomes. Stroke subtypes have differing distributions of risk factors, so this study aimed to explain the relationship between body mass index (BMI) and functional prognosis according to stroke subtype. Methods A prospective institutional database on stroke was accessed between March 2014 and December 2021, and consecutive patients with ischemic stroke were retrospectively selected. BMI was categorized into five groups (underweight, normal weight, overweight, obese, and morbid obesity). The outcome of interest in this study was the modified Rankin Scale (mRS) at 90 d, which was divided into favorable (mRS = 0–2) and unfavorable (mRS ≥ 3) groups. The relationship between functional outcome and BMI was analyzed according to stroke subtype. Results Among 2779 patients with stroke, 913 (32.9%) had unfavorable outcomes. After a propensity score-matched analysis, obesity was inversely associated with unfavorable outcomes (adjusted odds ratio [aOR] = 0.61, 95% confidence interval [95% CI]: 0.46–0.80) in all patients with stroke. Among the stroke subtypes, overweight (aOR = 0.38, 95% CI: 0.20–0.74) and obese (aOR = 0.40, 95% CI: 0.21–0.76) groups were inversely associated with unfavorable outcomes in the cardioembolism subtype. Obesity (aOR = 0.55, 95% CI: 0.32–0.95) was inversely associated with unfavorable outcomes in the small vessel disease subtype. There was no significant relationship between stroke outcome and BMI classification in the large artery disease subtype. Conclusions These findings suggest that the obesity paradox in ischemic stroke outcomes might differ according to the stroke subtype.