Adiposity and ischemic and hemorrhagic stroke: Prospective study in women and meta-analysis

Abstract

Objective: To compare associations of body mass index (BMI) with ischemic stroke and hemorrhagic stroke risk, and to review the worldwide evidence.

Methods: We recruited 1.3 million previously stroke-free UK women between 1996 and 2001 (mean age 57 years [SD 5]) and followed them by record linkage for hospital admissions and deaths. We used Cox regression to estimate adjusted relative risks for ischemic and hemorrhagic (intracerebral or subarachnoid hemorrhage) 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 9,993 were specified as ischemic and 5,852 as hemorrhagic. Increased BMI was associated with an increased risk of ischemic 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 hemorrhagic stroke (relative risk 0.89 per 5 kg/m² BMI, 0.86-0.92, p < 0.0001). The BMI-associated trends for ischemic and hemorrhagic stroke were significantly different (heterogeneity: p < 0.0001) but were not significantly different for intracerebral hemorrhage (n = 2,790) and subarachnoid hemorrhage (n = 3,062) (heterogeneity: p = 0.5). Published data from prospective studies showed consistently greater BMI-associated relative risks for ischemic than hemorrhagic stroke with most evidence (prior to this study) coming from Asian populations.

Conclusions: In UK women, higher BMI is associated with increased risk of ischemic stroke but decreased risk of hemorrhagic stroke. The totality of the available published evidence suggests that BMI-associated risks are greater for ischemic than for hemorrhagic stroke.

Figure 1. Relative risks of ischemic and hemorrhagic stroke by BMI

Estimates are adjusted for age, region, deprivation, physical exercise, alcohol intake, and smoking. Relative risk for each category is plotted against the mean measured BMI in that category. The size of each square is proportional to the amount of statistical information contained. BMI = body mass index; CI = confidence interval. Published with permission from Adrian Goodill.

Figure 2. Relative risks of intracerebral and subarachnoid hemorrhage by BMI

Estimates are adjusted for age, region, deprivation, physical exercise, alcohol intake, and smoking. Relative risk for each category is plotted against the mean measured BMI in that category. The size of each square is proportional to the amount of statistical information contained. BMI = body mass index; CI = confidence interval. Published with permission from Adrian Goodill.

Figure 3. Stratified relative risks of hemorrhagic and ischemic stroke per 5 kg/m² increase in body mass index

Estimates are adjusted for age, region, deprivation, physical exercise, alcohol intake, and smoking, where appropriate. Person-years are classified by age at risk or baseline characteristics of participants. Dotted lines represent the respective relative risks per 5 kg/m² in all women. The size of each square is proportional to the amount of statistical information contained. CI = confidence interval. Published with permission from Adrian Goodill.

Figure 4. Meta-analysis of findings from this study and other published studies

Relative risks of hemorrhagic and ischemic stroke per 5 kg/m² increase in body mass index. Estimates are adjusted for at least age, sex, and smoking, where appropriate, but not for potential mediators (high blood pressure, high cholesterol, or diabetes). Dotted lines represent the respective relative risks per 5 kg/m² in all women. The size of each square is proportional to the amount of statistical information contained. 45 and up = 45 and Up Study; CNHS = China National Hypertension Survey; FS = Finland survey; JALS-EEC = Japan Arteriosclerosis Longitudinal Study–Existing Cohorts Combine; Jood = Swedish record linkage study; Kailuan = Kailuan study; KNHS = Korean National Health System; NHIC = National Health Insurance Corporation; NHS = Nurses' Health Study; PHS = Physicians' Health Study; SPP = Stroke Prevention Project; SWHS = Shanghai Women's Health Study. CI = confidence interval. Published with permission from Adrian Goodill.