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

Abstract

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 ≥ 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.

Body mass index and stroke incidence in a Japanese community: the Hisayama study

“…Some cohort studies have shown an increased risk of total stroke or ischemic stroke with elevating BMI, [8][9][10][11][12][13][14] which is in accord with the findings of the risk of ischemic stroke in our male subjects. On the other hand, other studies have found no association, [15][16][17][18] an inverse or a U-shaped association.…”

“…A similar independent association has been observed in other studies of stroke. 10,12,14 These findings, together with our present results, suggest a link between overweight/obesity and ischemic stroke independent of established risk factors. Some investigators have proposed that the increase in prothrombotic factors [27][28][29] and inflammatory markers, [30][31][32][33] and the enhancement of insulin resistance and metabolic syndrome 34 observed among overweight and obese individuals may have a role in their increased risk of ischemic stroke.…”

“…9,10,[12][13][14]19,22 In our study, however, the association between BMI and ischemic stroke was not attenuated even after adjusting for these risk factors. This finding indicates an independent effect of overweight and obesity on the development of ischemic stroke.…”

“…In the literature, the associations between BMI levels and the risk of hemorrhagic stroke have been inconsistent, with some studies showing a positive association, 8,11,14 and others showing no, a negative or a U-shaped, association. 9,12,13,16,19,21,22 In the present study, we did not find a clear association between BMI levels and hemorrhagic stroke in men or women.…”

“…7 Increased body mass index (BMI) is tightly related to an increased risk of coronary heart disease, 8 but its association with stroke is less well recognized because of conflicting results reported in the literature. Some cohort studies have found a positive association between BMI and the risk of stroke, [8][9][10][11][12][13][14] whereas others have shown no apparent association [15][16][17][18] or have even reported an inverse or a U-shaped association. [19][20][21][22] In Japan, no prospective study has provided incidence data on this issue nor observed a positive association between BMI and the risk of stroke until now.…”