Joint association of adiposity and smoking with mortality among U.S. adults

Assessment of death risk for different combinations of body-mass index (BMI) and smoking status among a nationally representative cohort of U.S. adults.

A total of 210,818 participants of the National Health Interview Surveys 1987-1995 were followed through 2006. Relative risks of death from all causes, cardiovascular disease (CVD), and cancer were estimated for each joint group of smoking and BMI by age, using Cox models with the adjustment for age, gender, education, and race.

Across all the joint groups of BMI and smoking, extremely obese and underweight current smokers were the two groups having the highest risks of death from all causes, CVD, and cancer. For example, among middle-aged adults, the hazard ratios of death from all causes were 4.47 (95% confidence interval [CI], 3.59-5.57) and 5.28 (4.38-6.37) for extremely obese and underweight current smokers, respectively. Overweight was associated with a higher risk of death in middle-aged never smokers, but not in the elderly or in current smokers.

The coexistence of obesity or underweight with current smoking was associated with an especially large risk of death and the associations of BMI with mortality varied by smoking status, age, and cause of death.