Obese young and middle-aged adults tend to have more medical problems such as diabetes, hypertension, and colon cancer, as well as increased death rates compared with their thin and normal-weight counterparts. However, a new study suggests that extra weight may be protective for the elderly. The researchers found that obese elderly people were less likely to die than those who were thin or normal weight, even after adjusting for differences in medical problems and income. Thus, weight goals appropriate for younger people may not be appropriate for the elderly, conclude David C. Grabowski, Ph.D., of the University of Alabama at Birmingham, and John E. Ellis, M.D., of the University of Chicago.
In a study supported in part by the Agency for Healthcare Research and Quality (National Research Service Award training grant T32 HS00084), they retrospectively analyzed a nationally representative sample of 7,527 community-dwelling people age 70 and older in 1984 to calculate the impact of body mass index (BMI) on their risk of death over an 8-year period. People in the lowest 10 percent of the BMI range (BMI less than 19) were termed thin, and those within the highest 165 percent of the distribution were classified as obese (BMI greater than 28). All individuals in between were considered normal weight.
The thin group had the highest mortality rate (54 percent), the obese group the lowest (33 percent), and normal-weight elderly were in the middle (37 percent). Adjustment for demographic factors, functional status, and health service use such as hospitalizations and nursing home visits, still showed that compared with normal-weight older people, obese older people were 14 percent less likely to die, and thin people were 1.5 times more likely to die. Further adjustment for income and medical conditions did not substantially alter these results. The study's biggest limitation was the inability to control for cigarette smoking, which is associated with increased mortality and lower body weight, and to separate the effects of obesity from physical inactivity and low fitness status.
See "High body mass index does not predict mortality in older people: Analysis of the longitudinal study of aging," by Drs. Grabowski and Ellis, in the July 2001 Journal of the American Geriatric Society 49, pp. 968-979.