Adiposity, Body Fat Distribution, and Risk of Major Stroke Types Among Adults in the United Kingdom

IMPORTANCE: Uncertainty persists regarding the independent association of general and central adiposity with major stroke types. OBJECTIVE: To determine the independent associations of general and central adiposity with risk of ischemic stroke, intracerebral hemorrhage, and subarachnoid hemorrhage. DESIGN, SETTING, AND PARTICIPANTS: Between 2006 and 2010, adults without prior stroke at recruitment in England, Scotland, and Wales were recruited into the UK Biobank prospective cohort study and were followed up through linkage with electronic medical records. Data were analyzed from September 2021 to September 2022. EXPOSURES: General adiposity (body mass index [BMI] calculated as weight in kilograms divided by height in meters squared) and central adiposity (waist circumference). MAIN OUTCOMES AND MEASURES: Incident ischemic stroke, intracerebral hemorrhage, and subarachnoid hemorrhage as recorded through record linkage with electronic hospital records. Cox regression estimated adjusted hazard ratios (HRs) by stroke type. RESULTS: Among 490 071 participants, the mean (SD) age was 56.5 (8.1) years, 267 579 (54.6%) were female, and 461 647 (94.2%) were White. During a median (IQR) of 12 (11.2-12.7) years follow-up, 7117 incident ischemic strokes, 1391 intracerebral hemorrhages, and 834 subarachnoid hemorrhages were identified. After mutual adjustment for waist circumference, BMI had no independent association with ischemic stroke (HR per 5-unit higher BMI, 1.04; 95% CI, 0.97-1.11), but was inversely associated with intracerebral hemorrhage (HR, 0.85; 95% CI, 0.74-0.96) and subarachnoid hemorrhage (HR, 0.82; 95% CI, 0.69-0.96). Waist circumference (adjusted for BMI) was positively associated with ischemic stroke (HR per 10-cm higher waist circumference, 1.19; 95% CI, 1.13-1.25) and intracerebral hemorrhage (HR, 1.17; 95% CI, 1.05-1.30), but was not associated with subarachnoid hemorrhage (HR, 1.07; 95% CI, 0.93-1.22). CONCLUSIONS AND RELEVANCE: In this large-scale prospective study, the independent and contrasting associations of BMI and waist circumference with stroke types suggests the importance of considering body fat distribution to stroke risk. Waist circumference was positively associated with the risk of ischemic stroke and intracerebral hemorrhage, while BMI was inversely associated with the risk of subarachnoid hemorrhage and intracerebral hemorrhage. This study also suggests that some adverse correlate of low BMI may be associated with an increased risk of intracerebral hemorrhage and subarachnoid hemorrhage, which warrants further investigation.