Body mass index and risk of stroke among Chinese men and women.

OBJECTIVE

The relationship between body mass index (BMI) and stroke incidence and mortality remains controversial, particularly in Asian populations.

METHODS

We conducted a prospective cohort study in a nationally representative sample of 169,871 Chinese men and women age 40 years or older. Data on body weight was obtained at baseline examination in 1991 using a standard protocol. Follow-up evaluation was conducted in 1999 to 2000, with a response rate of 93.4%.

RESULTS

After excluding those participants with missing body weight or height values, 154,736 adults were included in the analysis. During a mean follow-up of 8.3 years, 7,489 strokes occurred (3,924 fatal). After adjustment for age, gender, physical inactivity, urbanization, geographic variation, cigarette smoking, diabetes, and education, compared with participants of normal weight (BMI 18.5-24.9), relative hazard (95% confidence interval) of incident stroke was 0.86 (0.80-0.93) for participants who were underweight (BMI < 18.5), 1.43 (1.36-1.52) for those who were overweight (BMI 25-29.9), and 1.72 (1.55-1.91) for those who were obese (BMI > or = 30). The corresponding relative hazards were 0.76 (0.66-0.86), 1.60 (1.48-1.72), and 1.89 (1.66-2.16) for ischemic stroke and 1.00 (0.89-1.13), 1.18 (1.06-1.31), and 1.54 (1.27-1.87) for hemorrhagic stroke. For stroke mortality, the corresponding relative hazards were 0.94 (0.86-1.03), 1.15 (1.05-1.25), and 1.47 (1.26-1.72). Linear trends were significant for all outcomes (p < 0.0001).

INTERPRETATION

These results suggest that elevated BMI increases the risk of both ischemic and hemorrhagic stroke incidence, and stroke mortality in Chinese adults.