Body Mass Index and All-Cause Mortality Among Older Adults

Objective: To examine the association between baseline body mass index (BMI, kg/m(2)) and all-cause mortality in a well-characterized cohort of older persons. Methods: The association between BMI (both as a categorical and continuous variable) and all-cause mortality was investigated using 4,565 Geisinger Rural Aging Study participants with baseline age 74.0 +/- 4.7 years (mean +/- SD) and BMI 29.5 +/- 5.3 kg/m(2) over a mean of 10.9 +/- 3.8 years of follow-up. Results: The relationship between BMI (as a continuous variable) and all-cause mortality was found to be U-shaped (P nonlinearity <0.001). Controlling for age, sex, smoking, alcohol, laboratory values, medications, and comorbidity status, underweight (BMI <18.5 kg/m(2)) individuals had significantly greater adjusted risk of all-cause mortality than persons of BMI 18.5 to 24.9 kg/m(2) (reference range). Participants with overweight (BMI 25.0-29.9 kg/m(2)) and class I obesity (BMI 30.0-34.9 kg/m(2)) had significantly lower adjusted-risk of all-cause mortality. Those with classes II/III obesity (BMI >= 35.0 kg/m(2)) did not have significantly greater adjusted-risk of all-cause mortality. Findings were consistent using propensity score weights and among never-smokers with 2- and 5-year lag analysis and among those with no identified chronic disease. Conclusions: A U-shaped association was observed between BMI and all-cause mortality with lower risk among older persons with overweight and class I obesity in comparison with those with BMI 18.5 to 24.9 kg/m(2).