Older Americans are losing as much as three-and-a-half healthy years because they are obese, have knee osteoarthritis or are dealing with both conditions, according to a study published in the February 15, 2011, Annals of Internal Medicine.

“One, two, three years – these are meaningful, especially when you get to your 60s and 70s, where every year really matters because there are fewer left,” says study author Elena Losina, PhD, co-director of the Orthopedics and Arthritis Center for Outcomes Research at Brigham and Women’s Hospital in Boston.

Quality-of-life years, or healthy years, are determined by the amount of illness, disability, pain and functional limitation a person has during any given year. Researchers created a mathematical formula to determine the impact obesity and knee OA have on quality of life years – which is different than mortality because it’s looking not at the length of life, but instead the quality of life in terms of things like functionality and activity.

Based on U.S. Census and obesity data and prevalence rates of knee OA, researchers determined that 40 percent of Americans ages 50 to 84 have both conditions. That’s about 2.9 million Americans with 3.5 fewer healthy years than those who are a healthy weight and don’t have knee OA.

The nearly 29 million older Americans who are obese but don’t have knee OA could lose about 2.5 healthy years, and another 2.8 million who have knee OA but aren’t obese will lose almost 1.9 healthy years.

“[We hope that] the fact that quality of life is diminished makes it clear that if you prevent the conditions, your years of healthy life will be increased,” Losina explains.

Researchers say data shows that 55 percent of African-American women and 50 percent of Hispanic women are either obese, have knee OA or both, compared with just 38 percent of white women. So these findings, they say, are especially important to these minority groups.

“I think everyone needs to pay attention, but African-American and Hispanic women need to pay special attention,” Losina explains. “I think it’s really critical for interventions to address the needs and aspirations of these population groups because I think it will affect the efficacy of the intervention.”

Lawrence Cheskin, MD, is the director of the Johns Hopkins Weight Management Center and a professor at Johns Hopkins Bloomberg School of Public Health in Baltimore. He says even though the numbers are based on population averages – and thus are not accurate predictors for individuals – the general findings still have value.

“Unless you want to assume you will beat the odds, you should take it seriously and assume you will be no better than average. And if you are average, you [could] lose three-and-a-half years of [healthy] life.”

Dr. Cheskin says the numbers are also helpful because they put in context how detrimental the combination of obesity and OA are. But he says the important message is also that these figures aren’t set in stone.

“We are talking about something that is potentially alterable. Getting arthritis may not be alterable. On the other hand, how it progresses and how much disability you have from it can be in your control to a certain extent if you do something positive for your lifestyle, like lose weight if you are obese,” Dr. Cheskin says. “That’s within your control. It’s not easy but it’s at least potentially something you can positively impact in terms of your health and quality of life.”

Funding for this study came from The National Institutes of Health and the Arthritis Foundation.