Body mass index, blood pressure, and mortality from stroke: a nationally representative prospective study of 212,000 Chinese men.

BACKGROUND AND PURPOSE: Despite previous investigations, substantial uncertainty remains about the relation between body mass index (BMI) and stroke, especially in populations with a relatively low BMI but a high stroke rate. METHODS: A nationally representative prospective study of mortality included 212,000 Chinese men 40 to 79 years old without known cardiovascular disease in 1990 to 1991 who were followed up for 10 years. Standardized hazard ratios were calculated for stroke mortality by baseline systolic blood pressure (SBP) and BMI. RESULTS: Mean SBP and BMI were 124 mm Hg and 21.7 kg/m(2), respectively. During 10 years of follow-up, 5766 stroke deaths were recorded. There were strong, positive relations between BMI and SBP and between SBP and stroke mortality, with a 3-mm Hg higher baseline SBP associated with a 5.6% (95% CI, 5.3% to 6.0%; P<0.00001) higher stroke mortality. The association between BMI and stroke mortality was, however, not linear, with the hazard increasing substantially only for BMI >25 kg/m(2) (P<0.001 for nonlinearity). Approximately 90% of men had a baseline BMI <25 kg/m(2), and among them, BMI was not associated with stroke mortality despite its strong association with BP (which continued to a BMI <18 kg/m(2)). The relation with BMI was similar for ischemic and hemorrhagic stroke but appeared to be steeper among lifelong nonsmokers than among current smokers (P=0.01 for difference between slopes) despite similarly positive relations between BMI and SBP and between SBP and stroke risk in both smoking categories. CONCLUSIONS: High BMI was strongly associated with increased stroke mortality only among men who were overweight or obese.

Esophageal cancer and body mass index: results from a prospective study of 220,000 men in China and a meta-analysis of published studies.

Several epidemiological studies have reported on the association between body mass index (BMI) and risk of esophageal cancer, but these were mostly in Western populations where many are overweight or obese. There is little direct evidence about the relationship in China where the mean BMI is relatively low and the disease rate is high. We examined the data from a population-based prospective study of 220,000 Chinese men aged 40-79 without a previous history of cancer (mean BMI 21.7 kg/m(2)), which included 1,082 esophageal cancer deaths during 10 years of follow-up. Adjusted hazard ratios for death from esophageal cancer by baseline BMI category were calculated using Cox proportional hazards models. Even among men with good self-assessed health and BMI >or= 18.5 kg/m(2), there was a strong inverse association between BMI and death from esophageal cancer, with each 5 kg/m(2) higher BMI associated with 25% (95%CI: 11-36%) lower esophageal cancer mortality. This inverse association persisted when analysis was restricted to men who had never smoked or when the first 5 years of follow-up were excluded. The strength of the relationship was consistent with the pooled estimate for squamous cell carcinoma of the esophagus in a meta-analysis of prospective studies (31% lower relative risk per 5 kg/m(2) higher BMI; 95% CI: 25-37%), but contrasted with that for adenocarcinoma which showed a positive association with BMI. Together, these data provide reliable evidence that in many populations low BMI is associated with an increased risk of squamous cell carcinoma of the esophagus.