Background: The US Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults set the body mass index (BMI; weight in kilograms divided by the square of height in meters) of 25 as the upper limit of ideal weight for all adults regardless of age. However, the prognostic importance of overweight and obesity in elderly persons (>/=65 years) is controversial. We sought to analyze the guidelines in the context of currently available evidence that is relevant to older adults.
Methods: We searched MEDLINE for all English-language studies of the association between BMI and all-cause or cardiovascular mortality or coronary heart disease events from January 1966 through October 1999. Additional pertinent articles were identified through bibliographies of the MEDLINE articles. We selected studies for detailed review if they reported on the association between BMI and mortality for nonhospitalized subjects who were 65 years or older and had been followed up for at least 3 years. We controlled for age, smoking, and baseline health status. Of the 444 screened articles, 13 were selected to assess the guidelines. We extracted information regarding publication year, study design, population, recruitment period, follow-up duration, number of subjects, sex, age range, inclusion and exclusion criteria, and statistical models, including variables and end points.
Results: These data do not support the BMI range of 25 to 27 as a risk factor for all-cause and cardiovascular mortality among elderly persons. The results were not substantially different for men and women. Most studies showed a negative or no association between BMI and all-cause mortality. Three studies indicated overweight (BMI >/=27) as a significant prognostic factor for all-cause and cardiovascular mortality among 65- to 74-year-olds, and one study showed a significant positive association between overweight (BMI >/=28) and all-cause mortality among those 75 years or older. Higher BMI values were consistent with a smaller relative mortality risk in elderly persons compared with young and middle-aged populations.
Conclusions: Federal guideline standards for ideal weight (BMI 18.7 to <25) may be overly restrictive as they apply to the elderly. Studies do not support overweight, as opposed to obesity, as conferring an excess mortality risk. Future guidelines should consider the evidence for specific age groups when establishing standards for healthy weight.