BMI Risk Factors in Seniors Different Than in Younger Adults

Adults aged over 70 years who are classified as overweight are less likely to die over a ten-year period than adults who are in the "normal” weight range, according to a new study.

Researchers at the University of Western Australia (Perth, Australia) followed 4,677 men and 4,563 women (aged 70-75) who were recruited for the study in 1996 from the Australian Health in Men study and the Australian Longitudinal Study of Women's Health. The participants were followed for ten years or until their death, whichever was sooner, and factors such as lifestyle, demographics, and health were measured. The men and women were classified according to World Health Organization (WHO, Geneva, Switzerland) guidelines for body mass index (BMI) categories into underweight (BMI under 18.5), normal weight (BMI of 18.5–24.9), overweight (BMI 25–29.9), and obesity (BMI over 30). Relative risk of all-cause mortality and cause-specific (cardiovascular disease, cancer, and chronic respiratory disease) mortality were also examined.

The results showed that mortality relative risk of death for overweight participants was 13% less than for normal-weight participants. The risk of death was similar for obese and normal-weight participants. Being sedentary doubled the mortality risk for women across all levels of BMI, but resulted in only a 28% greater risk for men. In those participants who died before the conclusion of the study, the researchers concluded that the type of disease, which caused their death, did not affect the level of protection afforded by being overweight. To remove any risk of bias in participants with illnesses, which caused them to lose weight and increased their risk of dying, the researchers contrasted subjects who were relatively healthy compared with those who had major chronic diseases or smoked, and found no apparent differences in the BMI/mortality relationship. The study was published in the February 2010 issue of the Journal of the American Geriatrics Society.

"The objective of our study was to examine the major unresolved question of what level of BMI is associated with the lowest mortality risk in older people,” said lead author Professor Leon Flicker. "Our study suggests that those people who survive to age 70 in reasonable health have a different set of risks and benefits associated with the amount of body fat to younger people, and these should be reflected in BMI guidelines.”

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University of Western Australia