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

Abstract

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/kg(2)) 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.