A prospective study of body mass index and mortality in Bangladesh

Background: Body mass index (BMI) (kg/m²) has a U-or J-shaped relationship with all-cause mortality in Western and East Asian populations. However, this relationship is not well characterized in Bangladesh, where the BMI distribution is shifted towards lower values. Methods: Using data on 11 445 individuals (aged 18-75 years) participating in the Health Effects of Arsenic Longitudinal Study (HEALS) in Araihazar, Bangladesh, we prospectively examined associations of BMI (measured at baseline) with all-cause mortality during ~6 years of follow-up. We also examined this relationship within strata of key covariates (sex, age, smoking, education and arsenic exposure). Cox proportional hazards models adjusted for these covariates and BMI-related illnesses were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for BMI categories defined by the World Health Organization. Results: Low BMI was strongly associated with increased mortality in this cohort (P-trend < 0.0001). Severe underweight (BMI < 16 kg/m²; HR 2.06, CI 1.53-2.77) and moderate underweight (16.0-16.9 kg/m²; HR 1.39, CI 1.01-2.90) were associated with increased all-cause mortality compared with normal BMI (18.6-22.9 kg/m²). The highest BMI category (≥23.0 kg/m²) did not show a clear association with mortality (HR 1.10, CI 0.77-1.53). The BMI-mortality association was stronger among individuals with <5 years of formal education (interaction P=0.02). Conclusions: Underweight (presumably due to malnutrition) is a major determinant of mortality in the rural Bangladeshi population.