Prospective study of body mass index and risk of stroke in apparently healthy women.
BACKGROUND
Obesity is an escalating pandemic in the United States, and its association with coronary heart disease is well understood. Several studies have found positive associations between body mass index (BMI) and stroke in men, but the association with stroke and its subtypes is less clear in women.


RESULTS
This was a prospective cohort study among 39 053 women participating in the Women's Health Study. BMI was measured as self-reported weight (in kilograms) divided by height (in meters) squared. Incident stroke was self-reported and confirmed by medical record review. We used the Cox proportional hazards model to evaluate the association between BMI and stroke. After a mean follow-up of 10 years, a total of 432 strokes (347 ischemic, 81 hemorrhagic, and 4 undefined) occurred. We found a statistically significant trend for increased risk of total and ischemic stroke across 7 BMI categories. With World Health Organization criteria, women who were obese (BMI > or =30 kg/m2) had hazard ratios of 1.50 (95% CI 1.16 to 1.94) for total stroke, 1.72 (95% CI 1.30 to 2.28) for ischemic stroke, and 0.82 (95% CI 0.43 to 1.58) for hemorrhagic stroke compared with women with BMI <25 kg/m2. Additional control for history of hypertension, diabetes, and elevated cholesterol substantially attenuated the hazard ratios for total and ischemic stroke. There was no effect modification for age, exercise, or smoking.


CONCLUSIONS
In this large prospective cohort study among women, BMI was a strong risk factor for total and ischemic stroke but not for hemorrhagic stroke. The association was highly mediated by hypertension, diabetes, and elevated cholesterol.
Kurth
Tobias
T
Division of Preventive Medicine, Brigham and Women's Hospital, Harvard Medical School, 900 Commonwealth Ave E, Boston, MA 02215-1204, USA. tkurth@rics.bwh.harvard.edu
Gaziano
J Michael
JM
Rexrode
Kathryn M
KM
Kase
Carlos S
CS
Cook
Nancy R
NR
Manson
Joann E
JE
Buring
Julie E
JE
D015992:Body Mass Index; D002545:Brain Ischemia / Q000209:etiology; D002543:Cerebral Hemorrhage / Q000209:etiology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008875:Middle Aged; D015999:Multivariate Analysis; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012307:Risk Factors; D020521:Stroke / Q000145:classification / Q000453:epidemiology / Q000209:etiology*