Overweight Elderly Have Similar Mortality to Normal-Weight Elderly

Laurie Barclay, MD

January 28, 2010

January 28, 2010 — Current body mass index (BMI) thresholds for overweight and obesity may be overly restrictive for older people, according to the authors of a cohort study published online January 27 and in the February print edition of the Journal of the American Geriatrics Society.

"Obesity is a global epidemic that is prevalent in developed and developing countries; affects people of both sexes and all ages; and has negative health consequences (ill health, disability, and mortality), economic costs, and social implications," write Leon Flicker, PhD, from the University of Western Australia in Perth, and colleagues. "In industrialized countries, the prevalence of overweight and obesity in older people is a growing public health concern, particularly because sustained aging of their populations is expected to continue for many decades, and obesity and aging represent large components of healthcare spending."

The study goal was to assess all-cause and cause-specific mortality associated with underweight (BMI, <18.5), normal weight (BMI, 18.5 - 24.9), overweight (BMI, 25.0 - 29.9), and obesity (BMI, ≥30.0) in an older population. In the Health in Men Study and the Australian Longitudinal Study of Women's Health, 4677 men and 4563 women aged 70 to 75 years were recruited in 1996 and followed up for up to 10 years. The main study outcomes were relative risk for all-cause mortality and specific mortality related to cardiovascular disease, cancer, and chronic respiratory disease.

Overweight participants had lowest mortality risk, with risk for death for overweight participants 13% less than for normal-weight participants (hazard ratio [HR], 0.87; 95% confidence interval [CI], 0.78 - 0.94). Obese and normal-weight participants had similar risk for death (HR, 0.98; 95% CI, 0.85 - 1.11).

Across all levels of BMI, being sedentary doubled the mortality risk for women (HR, 2.08; 95% CI, 1.79 - 2.41) but was associated with only a 28% greater risk for men (HR, 1.28; 95% CI, 1.14 - 1.44).

"These results lend further credence to claims that the BMI thresholds for overweight and obese are overly restrictive for older people," the study authors write. "Overweight older people are not at greater mortality risk than those who are normal weight. Being sedentary was associated with a greater risk of mortality in women than in men."

Limitations of this study include observational design, measurement of height and weight only once at study entry, use of BMI as a surrogate measure of body fat, reliance on self-reported height and weight, and lack of generalizability to older people who are frail and at risk for death.

"A greater risk was found for extreme obesity," the study authors conclude. "Mortality risk must be balanced by the potential loss of physical function associated with obesity.... Overweight older people are not at greater mortality risk, and there is little evidence that dieting in this age group confers any benefit; these findings are consistent with the hypothesis that weight loss is harmful."

The Men, Women and Ageing project is funded by a National Health and Medical Research Council of Australia/Australian Research Council Ageing Well, Ageing Productively Strategic Award. The study authors have disclosed no relevant financial relationships.

J Am Geriatr Soc. Published online January 27, 2010. Print publication 2010;58:234-241.

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