Body mass index is inversely related to mortality in elderly subjects

PURPOSE: To study the long-term effect of being overweight on mortality in very elderly subjects. METHODS: The medical records of 470 inpatients (226 males) with a mean age of 81.5±7 years and hospitalized in an acute geriatric ward between 1999 and 2000 were reviewed for this study. Body mass index (BMI) at admission day was subdivided into quartiles: <22, 22-25, 25.01-28, and ≥28 kg/m². Patients were followed-up until August 31, 2004. Mortality data were taken from death certificates. RESULTS: During a mean follow-up of 3.46±1.87 years (median 4.2 years [range 1.6 to 5.34 years]), 248 patients died. Those who died had lower baseline BMI than those who survived (24.1±4.2 vs 26.3±4.6 kg/m²; p<.0001). The age-adjusted mortality rate decreased from 24 to 9.6 per 100 patient-years from the highest to lowest BMI quartile (p<.001). BMI was associated with all-cause and cause-specific mortality even after controlling for sex. A multivariate Cox proportional hazards model identified that even after controlling for male gender, age, renal failure, and diabetes mellitus, which increased the risk of all-cause mortality, elevated BMI decreased the all-cause mortality risk. CONCLUSIONS: In very elderly subjects, elevated BMI was associated with reduced mortality risk.