Knee Osteoarthritis, Obesity Reduce Quality of Life

Neil Osterweil

February 14, 2011

February 14, 2011 — Americans aged 50 years and older collectively lose about 86 million quality-adjusted life-years (QALYs) to knee osteoarthritis (OA), obesity, or a combination of these conditons, with black and Hispanic women at particularly high risk for associated morbidity and mortality, investigators report in the February 15 issue of the Annals of Internal Medicine.

A computer model the researchers created that takes into account race- and sex-specific prevalence of both knee OA and obesity and its associated comorbidities indicates that nonobese Americans from the ages of 50 to 84 years who have knee OA lose an estimated 1.857 per person QALYs. Obese adults with knee OA get a double whammy, losing an estimated 3.501 per person QALYs, write Elena Losina, PhD, from Brigham & Women's Hospital in Boston, Massachusetts, and colleagues.

Black and Hispanic women who are obese but without knee OA lose about 2.6 QALYs, whereas those with both conditions have a decrement of about 3.8 QALYs compared with their leaner, OA-free counterparts, the investigators report.

"The disproportionate burden these conditions impose on black and Hispanic women suggests that future studies should investigate tailoring prevention and treatment strategies to sex and racial or ethnic subpopulations," they write.

The authors note that patients are more likely to respond to messages about health-related behavioral changes if those messages offer the possibility of a benefit to them, and if the messages are presented using people of their own race and sex.

The researchers calculated that if the prevalence of obesity could be reduced to the levels seen a decade ago, there could be significant increases in life expectancy related to reductions in coronary heart disease, diabetes, and knee replacements.

Challenging to Find Weight Loss Strategies

Finding the right weight-loss strategy can be challenging for patients with knee OA, for whom some weight-bearing exercises may be contraindicated, but the ultimate payoff in better quality of life is worth the effort, said an OA expert interviewed by Medscape Medical News.

"If patients are able to carry out the recommendations, there's no question that they're going to improve symptomatically in terms of their long-term morbidity," said Roland Moskowitz, MD, director of the Rheumatology Clinical Research Unit at Case Western Reserve University in Cleveland, Ohio.

Nortin M. Hadler, MD, professor of medicine and microbiology/immunology at the University of North Carolina at Chapel Hill, told Medscape Medical News that although he admires the "extraordinary analysis" the authors conducted, by failing to consider socioeconomic status of the cohort members, the investigators "may be missing the forest for the trees."

"What we may be measuring here is not so much your body mass index interaction with the osteophytes in your knee, but which population among us — sizable population amongst us — is faced with less longevity and more morbidity, more likelihood to have problems that they remember and complain of, and they tend to be the lower quintile of socioeconomic status," Dr. Hadler said.

4 Populations Considered

Dr. Losina and colleagues used the Osteoarthritis Policy Model, a computer simulation, to examine the effects of knee OA and obesity in 4 cohorts of adults aged 50 to 84 years: people with neither knee OA nor obesity (reference group), those with either knee OA or obesity alone, and those with both.

The cohorts were drawn from US Census data and from data on obesity from the National Health and Nutrition Examination Survey and similar sources. They estimated mean QALYs lost for each group by subtracting the respective QALY estimates from the estimates for the reference group, and stratified the results by race/ethnicity and sex.

They found that "roughly 86 million [QALYs], comprising 8.4% of remaining quality-adjusted life expectancy, were lost over the remaining lifespan of a cohort of persons aged 50 to 84 years owing to obesity, symptomatic knee osteoarthritis, or both."

Most of the estimated loss — about 88% — they attributed to obesity and its associated metabolic and cardiovascular complications. They also note, however, that although knee OA does not have a direct effect on mortality, it "considerably reduces quality of life, thereby diminishing quality-adjusted life expectancy."

Their findings suggest that if obesity prevalence in the United States could be rolled back to turn-of-the millennium levels, there would be about 178,000 fewer cases of coronary heart disease, 890,000 fewer cases of diabetes, and 111,200 fewer total knee replacements, the authors write.

They acknowledge that their study was limited by their reliance on general population life expectancy data for estimates of comorbidity incidences, which may have underestimated the incidence rates in their study cohorts.

The study was supported by the National Institutes of Health and the Arthritis Foundation. Dr. Moskowtiz and Dr. Hadler have disclosed no relevant financial relationships.

Ann Intern Med. 2011;154:217-226.

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