Nov. 6, 2007 -- Here's yet another reason to maintain a healthy weight as you age: Obesity and disability are linked. Older adults who are obese develop more disabilities that interfere with daily living than older adults who are normal weight or slightly overweight, according to a new study.
For some types of disabilities, the risk among obese people is twice as great as among normal-weight people.
"It's not just that obese people have a higher risk [of these disabilities] than normal-weight people," says researcher Dawn Alley, PhD, a postdoctoral fellow at the Robert Wood Johnson Foundation Health and Society Scholars Program at the University of Pennsylvania, Philadelphia. "What is new about this research is that the risk is actually increasing in obese people over time."
Adults aged 60 and over who are slightly overweight did not have much of an increased risk of impairment, Alley says. But in those who were obese, the risk rose at a rate she considers "concerning." The more obese, the greater the risk, she found.
While previous research has suggested that the effect of obesity on disability remained constant over time, with disability rising in both the obese and the non-obese, the new study, published in the Nov. 7 issue of The Journal of the American Medical Association, suggests otherwise.
Obesity and Disability Linked
Alley and co-researcher Virginia W. Chang, MD, PhD, looked at the association between obesity and disability by analyzing data from a large national survey at two different time points. They looked at the National Health and Nutrition Examination Surveys for 1988 to 1994 and for 1999 to 2004. In all, they evaluated the obesity-disability association for nearly 10,000 adults aged 60 and older.
Obesity became more common over time. While 23.5% of participants in the first survey were obese, 31.7% of those in the second survey were.
Participants were classified as having a functional limitation if they had much difficulty or an inability to perform any of six everyday activities. These included walking a quarter mile, walking up 10 steps without resting, lifting or carrying 10 pounds, walking between rooms on the same floor, standing up from an armless chair, and the actions of stooping, crouching, and kneeling.
They also evaluated each participant's limitations in activities of daily living and classified them as limited if they had much difficulty or couldn't perform any of three tasks: getting in and out of bed, dressing themselves, and eating.
"At time point 1, obese older people were only 50% more likely than normal-weight people to be functionally impaired," says Alley. "At time point 2, they were 98% more likely to be functionally impaired than normal-weight people."
"The risk of functional impairment among obese elderly increased 24% over time," she tells WebMD.
During the first survey, the risk of having a limitation in daily living activities wasn't significantly different between obese and normal-weight participants. But by the second survey, the risk of having such difficulty was twice as great for obese people.
The increases are concerning for a couple of reasons, Alley says.
"One is, it means obese people are experiencing more potentially preventable impairments," she tells WebMD. "Second is that it means in the future, if this trend continues, increasing obesity rates are likely to slow health improvements in the elderly," such as better cardiovascular health due to better treatment.
"The change over time [in increased disability] is what is really surprising," Alley says.
The more obese, the higher the disability risk, the researchers also found. They classified the obese people in three segments:
- Those with a body mass index of BMI of 30 to 34.9
- Those with a BMI of 35 to 39.9
- Those with a BMI of 40 and above
A 5-foot 8-inch person who weighs 164 has a BMI of 24.9 (the top of the healthy range). A person the same height who weighs 197 has a BMI of 30; one who weights 263 has a BMI of 40.
More Obese People Becoming Disabled
"We've seen evidence for a while that obesity relates to disability," says Edward W. Gregg, PhD, an epidemiologist at the CDC's Division of Diabetes Translation, who co-authored an editorial to accompany the study. What the new study shows, however, is that more obese people are disabled than in the past.
That may be due, Gregg, Alley, and her co-researcher believe, to the fact that the people studied in the second time period have spent more years being obese than those studied in the first time period when obesity was not as common. In effect, the years of obesity have caught up with them.
That explanation makes sense to Roland Sturm, PhD, senior economist at the Rand Corp. in Santa Monica, Calif., who has published predictions about obesity causing more disability. "It's long been known than obesity has a lot do to with disability," he tells WebMD after reviewing the new study. "The new wrinkle here is, the effect of obesity on disability may have increased."
He adds: "The effects of obesity, just like the effects of smoking, only show up after a while."