Normal body mass index rather than obesity predicts greater mortality in elderly people: The jerusalem longitudinal study

OBJECTIVES: To examine the association between body mass index (BMI) and mortality in older people. DESIGN: A longitudinal cohort study of an age-homogenous, representative sample born in 1920/21. SETTING: Community-based home assessments. PARTICIPANTS: West Jerusalem residents born in 1920/21 examined at baseline in 1990 (n=447), with additional recruitment waves in 1998 (n=870) and 2005 (n=1,086). MEASUREMENTS: Comprehensive assessment of health variables including BMI (m/kg²) at ages 70, 78, and 85. The primary outcome of mortality was collected from age 70 to 88 (1990-2008). Adjusted Cox proportional hazards analysis was used to calculate hazard ratios (HRs) for mortality according to unit increase in BMI. RESULTS: A unit increase in BMI in women resulted in HRs of 0.94, (95% confidence interval (CI)=0.89-0.99) at age 70, 0.95 (95% CI=0.91-0.98) at age 78, and 0.91 (95% CI=0.86-0.98) at age 85. Similarly, in men, HRs were 0.99 (95% CI=0.95-1.05) at age 70, 0.94 (95% CI=0.91-0.98) at age 78, and 0.91 (95% CI=0.86-0.98) at age 85. A time-dependent analysis of 450 subjects followed for 18 years confirmed the above findings; a unit increase in BMI resulted in HRs of 0.93 (95% CI=0.87-0.99) in women and 0.93(95% CI=0.88-0.98) in men. Eliminating the first third of follow-up mortality to account for possibility of reverse causality did not change the results. CONCLUSION: Higher BMI was associated with lower mortality from age 70 to 88.