A PROSPECTIVE-STUDY OF BODY-MASS INDEX, WEIGHT CHANGE, AND RISK OF STROKE IN WOMEN

Objective.-To examine the associations of body mass index (BMI) and we ight change with risk of stroke in women. Setting and Design.-Prospect ive cohort study among US female registered nurses participating in th e Nurses' Health Study. Participants.-A total of 116 759 women aged 30 to 55 years in 1976 who were free from diagnosed coronary heart disea se, stroke, and cancer. Main Outcome Measure.-Incidence of ischemic st roke, hemorrhagic stroke (subarachnoid or intraparenchymal hemorrhage) , and total stroke. Results.-During 16 years of follow-up, 866 total s trokes (including 403 ischemic strokes and 269 hemorrhagic strokes) we re documented. In multivariate analyses adjusted for age, smoking, pos tmenopausal hormone use, and menopausal status, women with increased B MI (greater than or equal to 27 kg/m(2)) had significantly increased r isk of ischemic stroke, with relative risks (RRs) of 1.75 (95% confide nce interval [CI], 1.17-2.59) for BMI of 27 to 28.9 kg/m(2); 1.90 (95% CI, 1.28-2.82) for BMI of 29 to 31.9 kg/m(2); and 2.37 (95% CI, 1.60- 3.50) for BMI of 32 kg/m(2) or more (P for trend<.001), as compared wi th those with a BMI of less than 21 kg/m(2). For hemorrhagic stroke th ere was a nonsignificant inverse relation between obesity and hemorrha gic stroke, with the highest risk among women in the leanest BMI categ ory (P for trend=.20). For total stroke the RRs were somewhat attenuat ed compared with those for ischemic stroke but remained elevated for w omen with higher BMI (P for trend<.001). In multivariate analyses that also adjusted for BMI at age 18 years, weight gain from age 18 years until 1976 was associated with an RR for ischemic stroke of 1.69 (95% CI, 1.26-2.29) for a gain of 11 to 19.9 kg and 2.52 (95% CI, 1.80-3.52 ) for a gain of 20 kg or more (P for trend<.001), as compared with wom en who maintained stable weight (loss or gain <5 kg). Although weight change was not related to risk of hemorrhagic stroke (P for trend=.20) , a direct relationship was observed between weight gain and total str oke risk (P for trend<.001). Conclusions.-These prospective data indic ate that both obesity and weight gain in women are important risk fact ors for ischemic and total stroke but not hemorrhagic stroke. The rela tionship between obesity and total stroke depends on the distribution of stroke subtypes in the population.