THE RELATIONSHIP BETWEEN BODY-WEIGHT AND MORTALITY - A QUANTITATIVE-ANALYSIS OF COMBINED INFORMATION FROM EXISTING STUDIES

OBJECTIVE: To estimate the relationship between body mass index (BMI, kg/m(2)) and all-cause mortality with information from the published s cientific literature. DESIGN: Meta-analysis using a hierarchical, mixe d model. The analysis included random effects for information sources and fixed effects for factors that may modify the BMI-mortality relati onship such as smoking, control for disease, and country of origin, wh ich allowed combining information from diverse studies. MAIN OUTCOME M EASURES: Predicted probability of death over a given duration of follo w-up plotted by BMI for sex-age cohorts of white race. RESULTS: An ext ensive search identified nineteen prospective cohort studies that met inclusion criteria. A U-shaped relationship between BMI and mortality was demonstrated for 50-year-old men followed for 30 years. Mortality risk increased with low and high BMI (<23 or >28) in groups of non-smo kers without evidence of disease upon study entry. Limited information from studies of women indicated that, with 10 year follow-up, there w as little relationship between BMI and mortality for (1) non-smokers a nd for (2) mixtures of smokers and non-smokers. CONCLUSION: This quant itative analysis of existing studies revealed increased mortality at m oderately low BMI for white men comparable to that observed at extreme overweight, which does not appear to be due to smoking or existing di sease, Attention to the health risks of underweight is needed, and bod y weight recommendations for optimum longevity need to be considered i n light of these risks.