Physical Functioning Better Predictor of Death than Disease Among Elderly

The July 2008 issue of the American Journal of Public Health includes a study that shows that in people 80 and older, limits on a person's physical functioning are a better predictor of death within five years, than the presence of chronic diseases. The researchers, from the San Francisco VA Medical Center, looked at data from 19,430 participants from an ongoing National Institute on Aging. For those aged 50 to 59, chronic disease conditions were better indicators of mortality than functional measures. In older participants, the results shifted and functional limitations, became a better predictor.

Sei Lee, MD, MAS, a geriatrics researcher and assistant adjunct professor at UCSF believes there are two possible causes of the change.

The first is what he calls “a selection or survival effect.” For a younger person, he explains, high blood pressure or diabetes “can be a very bad thing, with a likelihood of very bad consequences. But if you’re 80, and you’ve lived with high blood pressure for 30 years, it’s possible that it just doesn’t mean the same thing to you as it does to the average person –– that your body has adjusted to it in some way. And so it won’t have nearly as much bearing on your chances of living another five years as your ability to walk down the block unaided or manage your own medications without help.”

Another potential reason has to do with the “trajectory of decline among our oldest subjects,” he says. Younger people are more likely to have a clear single cause of decline, he says, such as a heart attack or pneumonia. Older people, by contrast, are more likely to decline slowly, not as a result of one catastrophic event but “slowly, month by month, week by week, for no clear reason that you can put your finger on. Functional measures are much more likely to capture that trajectory of decline.”

Lee notes that functional status is known to be an important component of quality of life for older people. “Most older patients will tell you that they are more afraid of losing their independence than they are of dying,” he says.

As a follow up to the current study, Lee says that “even though self-reporting is well-known to be a valid indicator of health status, it would make sense to replicate this work with a larger sample and an objective data set such as formal medical records.”

If his results are validated, he says, “I would strongly advocate that functional status become a standard component of medical records. It would be an important tool for policy makers, clinicians, and patients.”