Race and Gender: Key Factors in Lifetime Knee Osteoarthritis RiskAfrican-American Women Most at Risk

Newswise — WASHINGTON – Race and ethnicity, along with gender, are important factors in determining both short-term and lifetime risk of developing symptomatic knee osteoarthritis, according to new research findings presented this week at the American College of Rheumatology Annual Meeting in Washington, D.C.

Knee osteoarthritis is caused by cartilage breakdown in the knee joint. Factors that increase the risk of knee osteoarthritis include obesity, age, prior injury to the knee, extreme stress to the joints, and family history. In 2005, 27 million Americans suffered from osteoarthritis, and one in two people will have symptomatic knee arthritis by age 85.

Researchers at Brigham and Women’s Hospital in Boston used a validated computer simulation model (the Osteoarthritis Policy model) with data from published studies to project short-term and lifetime risk of diagnosed symptomatic knee osteoarthritis based on gender, as well as race and ethnicity.

“We know that osteoarthritis of the knee is a very prevalent and disabling condition. We also know that the only definitive, curative treatment for knee OA right now is total knee replacement surgery,” says Elena Losina, PhD, co-director of Orthopedic and Arthritis Center for Outcomes Research at Brigham and Women’s Hospital in Boston, and lead investigator in the study. Dr. Losina and her colleagues sought data to show what segments of the population were most at risk of developing knee OA and most likely to need total knee replacement over their lifespan.

The study’s results showed that in people free of knee OA at age 40, the lifetime risk of developing knee OA ranged from 10 percent in white men to 17 percent in African-American women. While the risk for developing symptomatic knee OA increases with age, the disease can develop in relatively young individuals: 11.3 percent of African-American, 10.5 percent of Hispanic and 10 percent of white women free of the disease at age 40 will develop it by age 65.

“It is often perceived that osteoarthritis is a disease of older age. So if you’re 40, you are not worried about it. Our analyses indicated that three of 100 African American women are likely to be diagnosed with symptomatic knee osteoarthritis by age 50 and five of 100 by age 65,” Dr. Losina says. “We need people to start thinking about prevention earlier. We don’t want to send prevention messages at 50 or 60. We need to promote awareness of osteoarthritis risk much earlier so that prevention can work.”

“Higher rates of obesity among African-American and Hispanic women may contribute to the higher rates of knee OA risk seen in the study,” says Jeffrey N. Katz, MD, professor of medicine and Orthopedic Surgery at Harvard Medical School, a senior author of the study.

“We know that obesity is a risk factor for developing knee osteoarthritis. Reducing obesity is likely to reduce the risk of knee osteoarthritis and the need for total knee replacement,” Dr. Losina says. Prevention messages about increasing physical activity and managing weight may be more effective if they are targeted to each unique population group, Dr. Losina added.

Funding for this study was provided in part by the National Institute of Arthritis and Musculoskeletal and Skin Diseases of the National Institutes of Health.

The American College of Rheumatology is an international professional medical society that represents more than 9,000 rheumatologists and rheumatology health professionals around the world. Its mission is to advance rheumatology. The ACR/ARHP Annual Meeting is the premier meeting in rheumatology. For more information about the meeting, visit www.acrannualmeeting.org or join the conversation on Twitter by using the official hashtag: #ACR2012.

Editor’s Notes: Elena Losina, PhD, MSc will present this research during the ACR Annual Meeting at the Walter E. Washington Convention Center at 9:00 - 11:00 AM on Monday, November 12 in Poster Hall (Hall B). Dr. Losina will present this research during the ACR Annual Meeting at the Walter E. Washington Convention Center at 8:30 AM on Tuesday, November 13 in the on-site press conference room, Room 203 A-B.

Presentation Number: 911

Race- and Sex-Specific Estimates of 10-, 20-, 30-Year, and Lifetime Risk of Diagnosed Symptomatic Knee Osteoarthritis and the Need for TKR in the US

Elena Losina (Brigham and Women's Hospital, Boston, Mass.)Meghan E. Daigle(Brigham and Women's Hospital, Boston, Mass.)Sara A. Burbine (Brigham and Women's Hospital, Boston, Mass.) Jeffrey N. Katz (Brigham and Women's Hospital, Boston, Mass.)

Background/Purpose: A growing body of evidence suggests that females are more likely to be diagnosed with knee osteoarthritis (OA) and that obesity increases the risk of knee OA. Population-based studies suggest that Black and Hispanic females have a greater likelihood of being obese than White females. Sex- and race/ethnicity-specific risks of diagnosed symptomatic knee OA and the need for TKR have not been estimated.

Methods: We combined the OAPol Model – a validated state-transition, computer simulation model – with published data on the incidence of OA, stratified by sex and obesity. Obesity prevalence, stratified by sex and race/ethnicity, was derived from published literature and ranged from 19% for White males to 34% for Black females. The increased risk of symptomatic knee OA conferred by obesity was derived from published studies (RR = 1.7). Rates of progression of knee OA were derived from the Johnston County Osteoarthritis Project and calibrated to published data. The annual incidence of TKR among persons with advanced knee OA (Kellgren-Lawrence grade 3 or 4) was derived using data from two national longitudinal studies of persons with knee OA (Multicenter Osteoarthritis Study and Osteoarthritis Initiative). Input parameters related to mortality, obesity, comorbidities, non-surgical OA treatments, and implant failure were obtained from national survey data and published literature. Using the OAPol Model we estimated the 10-year, 20-year, 30-year and lifetime risks of diagnosed symptomatic knee OA and TKR from age 40, stratified by race and sex.

Results: In persons free of knee OA at age 40, the lifetime risk of diagnosed symptomatic knee OA ranged from 10% among White males to 17% among Black females (Figure). The 20-year risk of diagnosed symptomatic knee OA ranged from about 6% in males (race/ethnicity did not affect the rate meaningfully) to 8% in Black females. By age 65, 11.3%, 10.5%, and 10% of Black, Hispanic, and White females, free of knee OA at age 40, will be diagnosed with symptomatic knee OA (Figure). Lifetime need for TKR ranged from 3.8% for Hispanic males to 6.8% for Black females.

Conclusion: Lifetime risk of diagnosed symptomatic knee OA varies by age and race/ethnicity. Black females are more likely to be obese, which corresponds with their having the greatest lifetime risk of being diagnosed with knee OA and needing TKR. Race- and sex-tailored weight management programs may reduce the lifetime risk of knee OA. Disclosure: E. Losina, None; M. E. Daigle, None; S. A. Burbine, None; J. N. Katz, None.