MONDAY, Feb. 14 (HealthDay News) -- Obesity and osteoarthritis of the knee are robbing millions of older Americans of an average of 3.5 years of life in which they might otherwise be feeling healthy and free of chronic pain, new research finds.
Some 40 percent of older Americans are either obese and/or have osteoarthritis of the knee, an often painful and potentially disabling condition that can be exacerbated by carrying around extra weight.
To determine the toll of both conditions on those aged 50 to 84, researchers created a mathematical model to calculate "quality-adjusted life-year losses," or years of good health lost. This is different from mortality -- researchers did not focus on overall lifespan, but instead on quality of life.
"You take two people, one who doesn't have knee osteoarthritis and the other who does," said study author Elena Losina, an associate professor of orthopedic surgery at Harvard Medical School. "It makes him unable to walk more than one block. He has a hard time getting up in the morning and going to the bathroom. It really, really puts limitations on what he can do."
About 3.3 percent, or some 2.9 million Americans, are both obese and have knee osteoarthritis, which occurs when the cartilage between the joints deteriorates. As a result, they are projected to enjoy 3.5 years less of pain-free good health than those who are neither obese nor have osteoarthritis.
About 33.4 percent, or nearly 29 million older Americans, are obese and do not have osteoarthritis. They're projected to lose, on average, about 2.5 healthy, pain-free life-years, according to the study.
About 3.3 percent are not obese but have knee osteoarthritis anyway. They're projected to lose nearly 1.9 years of good health.
The study is published in the Feb. 15 issue of the Annals of Internal Medicine.
Simply telling people to lose weight to avoid knee osteoarthritis, or even warning that 3.3 percent of obese people have knee osteoarthritis, doesn't necessarily convey risk very well, Losina said.
"But if you say, 'There is a likelihood your lifespan will be 3.5 healthy life-years less than if you were not obese,' it's easier to understand," Losina said. "We hope that by using this matrix it would create more incentives for people to live a healthy lifestyle, control their weight and exercise now [that] they know what's at stake."
Even reducing obesity levels to where they were about 10 years ago would help hundreds of thousands of people aged 50 to 84 avoid osteoarthritis of the knee and eventual knee replacement surgery, according to the study.
And the knees wouldn't be the only body part feeling better. Rolling back obesity even slightly (say, a reduction of 3.74 pounds in a person about 5 feet, 7 inches tall) would also avert 178,000 cases of coronary heart disease and 890,000 cases of diabetes, the researchers reported.
In the study, black and Hispanic women were the hardest hit by obesity and knee osteoarthritis, with some 55 percent of black women and 50 percent of Hispanic women being either obese and/or suffering from knee osteoarthritis, compared to 38 percent of white women.
Osteoarthritis is a common cause of disability, and the knee is the most common place people are afflicted, according to background information in the article.
Dr. Evan McDevitt, an orthopedic surgeon at Bay Area Orthopaedics & Sports Medicine in Arnold, Md., said it's often knee pain that brings patients to see him. When he X-rays their knees, he also notices plaques in the artery that runs behind the knee.
"They want the knee replacement, but I tell them, it's not the osteoarthritis that's going to kill you," McDevitt said. "They have vascular disease. I tell them, 'You have to go get your cholesterol and lipids checked. Lower your blood pressure. Your obesity may be causing osteoarthritis of the knee, but it's also causing plaque formation that can lead to death.'"
The American Academy of Family Physicians has more on knee osteoarthritis.