The effect of middle- and old-age body mass index on short-term mortality in older people

OBJECTIVES: To determine the effect of body mass index (BMI) at old age and at age 50 on short-term survival among persons age 65 and older. DESIGN: Cross-sectional, using the 4,791 respondents to the community interview of the 1994 National Long Term Care Survey (NLTCS). SETTING: United States of America. PARTICIPANTS: Persons age 65 and older who lived in community settings as of the 1994 NLTCS interview. MEASUREMENTS: Short-term mortality was measured from the date of the 1994 NLTCS through year-end 1995. BMI (kg/m(2)) (at three points: 1994 NLTCS, 1 year before, age 50) and all other variables, including three other modifiable risk factors known to be related to mortality-cigarette smoking, alcohol consumption, and exercise-were based on self-report. RESULTS: Both the unadjusted and adjusted nadirs of mortality in relation to BMI at old age were found in older persons with a BMI between 30 and 34.9; this was true for males and females in all age groups. The highest mortality rates were found for older persons with very low BMI (< 18.5). In contrast, BMI at age 50 was positively related to mortality, with those in the lowest BMI category (< 18.5) at age 50 having the lowest mortality. Persons who were obese at age 50 and who were no longer obese at the 1994 NLTCS had lower mortality than persons with stable weight. CONCLUSIONS: Weight reduction by middle-aged persons who are obese should be reinforced as a public health priority, because there is evidence that long-term weight loss results in better short-term survival. Further study of healthy older survivors to determine why they are not harmed by heavier weight in old age may provide useful insights into successful aging.