Body mass index, diabetes, hypertension, and short-term mortality: a population-based observational study, 2000-2006

Abstract

Background: Published studies about the association of obesity with mortality have used body mass index (BMI) data collected more than 10 years ago, potentially limiting their current applicability, particularly given evidence of a secular decline in obesity-related mortality. The objective of this study was to examine the association between BMI and mortality in a representative, contemporary United States sample.

Methods: This was a population-based observational study of data from 50,994 adults aged 18 to 90 years who responded to the 2000 to 2005 Medical Expenditures Panel Surveys. Cox regression analyses were employed to model survival during up to 6 years of follow-up (ascertained via National Death Index linkage) by self-reported BMI category (underweight, <20 kg/m(2); normal weight, 20-<25 [reference]; overweight, 25-<30; obese, 30-<35; severely obese, ≥35), without and with adjustment for diabetes and hypertension. Survival by BMI category also was modeled for diabetic and hypertensive individuals. All models were adjusted for sociodemographics, smoking, and Medical Expenditures Panel Surveys response year.

Results: In analyses not adjusted for diabetes or hypertension, only severe obesity was associated with mortality (adjusted hazard ratio, 1.26; 95% confidence interval, 1.00-1.59). After adjusting for diabetes and hypertension, severe obesity was no longer associated with mortality, and milder obesity (BMI 30-<35) was associated with decreased mortality (adjusted hazard ratio, 0.81; 95% confidence interval, 0.68-0.97). There was a significant interaction between diabetes (but not hypertension) and BMI (F [4, 235] = 2.71; P = .03), such that the mortality risk of diabetes was lower among mildly and severely obese persons than among those in lower BMI categories.

Conclusions: Obesity-associated mortality risk was lower than estimated in studies employing older BMI data. Only severe obesity (but not milder obesity or overweight) was associated with increased mortality, an association accounted for by coexisting diabetes and hypertension. Mortality in diabetes was lower among obese versus normal weight individuals.