Body mass index categories and mortality risk in US adults: the effect of overweight and obesity on advancing death

Abstract

Objectives: We examined the association of body mass index with all-cause and cardiovascular disease (CVD)-specific mortality risks among US adults and calculated the rate advancement period by which death is advanced among the exposed groups.

Methods: We used data from the Third National Health and Nutrition Examination Survey (1988-1994) linked to the National Death Index mortality file with follow-up to 2006 (n = 16 868). We used Cox proportional hazards regression to estimate the rate of dying and rate advancement period for all-cause and CVD-specific mortality for overweight and obese adults relative to their normal-weight counterparts.

Results: Compared with normal-weight adults, obese adults had at least 20% significantly higher rate of dying of all-cause or CVD. These rates advanced death by 3.7 years (grades II and III obesity) for all-cause mortality and between 1.6 (grade I obesity) and 5.0 years (grade III obesity) for CVD-specific mortality. The burden of obesity was greatest among adults aged 45 to 64 years for all-cause and CVD-specific mortality and among women for all-cause mortality.

Conclusions: These findings highlight the impact of the obesity epidemic on mortality risk and premature deaths among US adults.

FIGURE 1—

Rate advancement periods by BMI category and age group for (a) all-cause mortality and (b) cardiovascular disease–specific mortality: Third National Health and Nutrition Examination Survey (1988–1994) and National Death Index linked mortality files with follow-up to 2006. Note. BMI = body mass index; RAP = rate advancement period. BMI was categorized as < 18.5 kg/m² (underweight), 18.5 kg/m² to < 25.0 kg/m² (normal weight), 25.0 kg/m² to < 30.0 kg/m² (overweight), 30.0 kg/m² to < 35.0 kg/m² (grade I obesity), 35.0 kg/m² to < 40.0 kg/m² (grade II obesity), and ≥ 40.0 kg/m² (grade III obesity).

FIGURE 2—

All-cause mortality rate advancement periods for BMI categories by gender: Third National Health and Nutrition Examination Survey (1988–1994) and National Death Index linked mortality files with follow-up to 2006. Note. BMI = body mass index; RAP = rate advancement period. BMI was categorized as < 18.5 kg/m² (underweight), 18.5 kg/m² to < 25.0 kg/m² (normal weight), 25.0 kg/m² to < 30.0 kg/m² (overweight), 30.0 kg/m² to < 35.0 kg/m² (grade I obesity), 35.0 kg/m² to < 40.0 kg/m² (grade II obesity), and ≥ 40.0 kg/m² (grade III obesity).