Underweight and mortality

Abstract

Objective According to most prospective studies, being underweight (BMI<185 kg/m(2)) is associated with significantly higher mortality than being of normal weight, especially among smokers. We aimed to explore in a generally lean population whether being underweight is significantly associated with increased all-cause mortality. Design: Prospective cohort study. Setting: Korea Medical Insurance Corporation study with 14 years of follow-up.Subjects After excluding deaths within the first 5 years of follow-up (1993-1997) to minimize reverse causation and excluding participants without information about smoking and health status, 94 133 men and 48 496 women aged 35-59 years in 1990 were included. Results: We documented 5411 (57 %) deaths in men and 762 (16 %) in women. Among never smokers, hazard ratios (HR) for underweight individuals were not significantly higher than those for normal-weight individuals (BMI=185-229 kg/m(2)): HR=087 (95 % CI 041, 184, P=072) for underweight men and HR=112 (95 % CI 076, 165, P=058) for underweight women. Among ex-smokers, HR=086 (95 % CI 038, 193, P=072) for underweight men and HR=377 (95 % CI 042, 3229, P=024) for underweight women. Among current smokers, HR=160 (95 % CI 128, 201, P<0001) for underweight men and HR=207 (95 % CI 043, 994, P=036) for underweight women. Conclusions: The present study does not support that being underweight per se is associated with increased all-cause mortality in Korean men and women.