Projects per year
Objective: To compare associations of body mass index (BMI) with ischaemic stroke and haemorrhagic stroke, and to review the worldwide evidence. Methods: We recruited 1.3 million previously stroke-free UK women between 1996 and 2001 (mean age 57 (sd 5)) and followed them by record linkage for hospital admissions and deaths. We used Cox regression to estimate adjusted relative risks for ischaemic and haemorrhagic (intracerebral or subarachnoid haemorrhage) stroke in relation to BMI. We conducted a meta-analysis of published findings from prospective studies on these associations. Results: During an average follow-up of 11.7 years, there were 20,549 first strokes of which 9993 were specified as ischaemic and 5852 as haemorrhagic. Increased BMI was associated with an increased risk of ischaemic stroke (relative risk 1.21 per 5 kg/m2 BMI, 95% confidence interval 1.18-1.23, P<0.0001) but a decreased risk of haemorrhagic stroke (relative risk 0.89 per 5 kg/m2 BMI, 0.86-0.92, P<0.0001). The BMI-associated trends for ischaemic and haemorrhagic stroke were significantly different (heterogeneity: P<0.0001) but were not significantly different for intracerebral and subarachnoid haemorrhage (heterogeneity: P=0.5). Published data from prospective studies showed consistently greater BMI-associated relative risks for ischaemic than haemorrhagic stroke with most evidence (prior to this study) coming from Asian populations. Conclusions: In middle-aged UK women, higher BMI is associated with increased risk of ischaemic stroke but decreased risk of haemorrhagic stroke. The totality of the available published evidence suggests that BMI-associated risks are greater for ischaemic than haemorrhagic stroke.