Overweight, Obesity, and Survival After Stroke in the Framingham Heart Study

Abstract

Background We investigated how body weight affects survival after stroke, leveraging the availability of multiple prestroke body mass index (BMI) measurements and using a nested case‐control design in a community‐based sample. Methods and Results We compared all‐cause mortality in participants stratified by prestroke weight. Separate analyses were performed for ischemic stroke and all stroke and for age‐, sex‐, and BMI category‐matched stroke‐free controls. Participants were grouped into BMI categories and followed for up to 10 years. Differences in survival were tested for interaction by case status. In sensitivity analysis, to exclude those with prestroke weight loss, we restricted the reference group to participants with 2 consistently normal BMI measurements within 10 years before stroke/matching. There were 782 stroke cases (age 71±9, 51% female participants, 87% ischemic stroke) and 2346 controls (age 72±9, 51% female participants). Overweight participants with ischemic stroke had a lower mortality compared with those with normal weight (hazard ratio [HR]=0.70, 95%CI 0.55‐0.90, P =0.005). The association of reduced mortality with BMI ≥25, compared with normal‐weight BMI 18.5 to <25, was pronounced among ischemic stroke cases but diminished with inclusion of hemorrhagic strokes (case‐control interaction P =0.051 and P =0.130, respectively). Compared with participants with stable normal weight, moderately increased weight was protective after ischemic stroke (overweight HR=0.72, 95%CI 0.53‐0.99, P =0.041). Conclusions Overweight and mildly obese participants had better 10‐year survival after ischemic stroke compared with normal‐weight participants, even after excluding persons with recent prestroke weight loss. There may be unknown protective factors associated with a moderately increased body weight before stroke.