Increasing Physical Activity in Adults with or at Risk for Osteoarthritis May Lead to Longer, Higher- Quality of Life with Less Money Spent in Health Care

Newswise — SAN DIEGO — Osteoarthritis patients who engage in regular physical activity have higher Quality- Adjusted Life Years, a standard measurement of quality of life and cost-effectiveness of medical treatment, according to new research findings presented this week at the American College of Rheumatology Annual Meeting in San Diego.

Osteoarthritis, or OA as it is commonly called, is the most common joint disease affecting middle-age and older people. It is characterized by progressive damage to the joint cartilage—the cushioning material at the end of long bones—and causes changes in the structures around the joint. These changes can include fluid accumulation, bony overgrowth, and loosening and weakness of muscles and tendons, all of which may limit movement and cause pain and swelling.

Knee osteoarthritis is a common form of osteoarthritis and is caused by cartilage breakdown in the knee joint. Factors that increase the risk of knee osteoarthritis include being overweight, age, injury or stress to the joints, and family history.

Researchers at Northwestern University and Feinberg School of Medicine in Chicago, Il, the University of Pittsburgh, and Brown University in Providence, R.I., analyzed data on physical activity levels in adults with or at risk for knee OA and their quality of life measurements using results from the Osteoarthritis Initiative (called OAI), a nationwide research study sponsored by the National Institutes of Health. The OAI includes questionnaire, laboratory tests and imaging results from more than 4,700 adults with or at risk for knee OA. The researchers wanted to determine if increased physical activity in OA patients would correlate to better Quality-Adjusted Life Years, or QALYs. QALYs are a measure of health outcomes based on both quality of life and survival duration a particular medical intervention would add to the patient’s life. Cost effectiveness for any treatment can then be determined by the cost needed to improve QALYs by one.

“Because physical activity conveys many health benefits, the Department of Health and Human Services published physical activity guidelines in 2008 for all Americans including those with osteoarthritis,” explains Kai Sun, MD; medical resident and research trainee; Northwestern Feinberg School of Medicine; and lead investigator in the study. “The guidelines recommend 150 minutes of moderate to vigorous activity a week performed in bouts lasting at least 10 minutes. The objective of our study was to investigate if meeting the 2008 DHHS physical activity guidelines translated into better QALYs among adults with or at risk for knee OA, and to postulate whether interventions to increase physical activity could be cost effective.”

Physical activity levels in these participants were measured for one week using accelerometers, and participants fell into three groups: those meeting national physical activity guidelines, insufficiently active, and inactive. Participants meeting guidelines had 150 or more minutes per week of moderate to vigorous physical activity in bouts of 10 or more minutes. Participants who were insufficiently active had some moderate to vigorous activity, but less than 150 minutes per week, and inactive participants had no bouts of moderate to vigorous activity lasting more than 10 minutes per week. Data were stratified by gender and body-mass index. Various socioeconomic and health factors like smoking, age, education levels, co-existing diseases, and knee OA symptoms were also taken into account. Physical activity was monitored at the beginning of the study (OAI 48-month follow-up visit). Health-related utility scores used to calculate QALYs were measured at the beginning of the study and then again two years later (OAI 72-month follow-up visit).

The researchers found a significant graded relationship between higher levels of physical activity and QALYs. Over the course of two years, those who met physical activity guidelines had QALYs that were 0.11 higher than those who were inactive, and even those who were insufficiently active had QALYs that were 0.058 higher than those who were inactive after adjusting for socioeconomic and health factors. These numbers represent about 10 to 20 additional days of perfect health over a year. Interventions to encourage adults to increase their physical activity level even if guidelines are not fully met could potentially translate to better quality of life, added years of healthy life, and thereby lower overall health care costs, the study’s authors concluded. They estimated that medical intervention costing $1,450 or less that resulted in increased moderate to vigorous physical activity in those with or at risk for knee OA would be cost-effective, using a $50,000 cut-off for additional cost per QALYs gained.

“Regular physical activity improves health and reduces mortality in the general population. Furthermore, physical activity promotes arthritis-specific health benefits including improving symptoms, function and psychosocial outcomes, as well as reduced disability,” says Dr. Sun. “Despite these benefits, the majority of adults in the U.S. do not attain the recommended amounts of physical activity. The costs associated with the treatment of inactivity-related diseases and injuries, lost productivity and diminished quality of life poses an economic burden. Therefore, promoting physical activity is an important component in promoting overall health, addressing the epidemic of obesity and other chronic illnesses, and reducing health care costs in the long term.”

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 http://www.acrannualmeeting.org/ or join the conversation on Twitter by using the official hashtag: #ACR13

Editor’s Notes: Dr. Sun will present this research during the ACR Annual Meeting at the San Deigo Convention Center at 2:30 PM on Sunday, October 27 in Hilton Room 306 A. Dr. Sun will be available for media questions and briefing at 1:30pm Monday, October 28 in the on-site press conference room, 27AB.

Abstract Number: 778

Relationship of Meeting Physical Activity Guidelines and Quality Adjusted Life Years

Kai Sun1, Jing Song1, Larry Manheim1, C. Kent Kwoh2, Rowland W. Chang3, Pamela A. Semanik1, Dorothy D. Dunlop1 and Charles Eaton4, 1Northwestern University, Chicago, IL, 2University of Pittsburgh, Pittsburgh, PA, 3Northwestern University Medical School, Chicago, IL, 4Brown University, Providence, RI

Background/Purpose: Regular physical activity is associated with reduced chronic disease burden and mortality. Recognizing the importance of physical activity, there are US federal guidelines for adults that also include persons with arthritis. Improving physical activity may be key to improving overall public health and reducing health care spending. Quality Adjusted Life Year (QALY) is a standard outcome measure used in cost-effectiveness analyses. We analyzed the data from the Osteoarthritis Initiative (OAI) to determine whether increasing levels of physical activity is correlated to larger QALY estimates.

Methods: Physical activity was measured using accelerometers and was classified as 1) Meeting Guidelines (≥150 moderate-to-vigorous [MV] minutes/week acquired in bouts ≥10 minutes); 2) Insufficiently Active (some but <150 MV bout minutes/week) or 3) Inactive (no bouts of MV activity lasting 10 minutes over the week). An SF6-D utility score (range 0-1) was derived from patient reported health status at baseline and 2 year follow-up. The QALY outcome was calculated as the area under utility curve over 2 years (range 0-2). Data were stratified by gender and body mass index (BMI). The relationship of physical activity levels to median QALY adjusted for sociodemographic factors (age, gender, race, education, income) and clinical/health factors (body mass index, medical comorbidity, smoking, presence of radiographic knee osteoarthritis, knee symptoms, and prior knee injury) was derived using median quantile regression.

Results: Median QALYs over 2 years were significantly higher with greater physical activity level in a stepwise fashion as shown by the cumulative frequency curve (figure). Relative to the Inactive group, the median QALYs of the Meeting Guidelines group was 0.162 (95% confidence interval (CI) 0.120-0.204)higher, and that of the Insufficiently Active group was 0.082 (95% CI 0.052-0.110) higher. After adjusting for sociodemographic and clinical/health factors, the differences in median QALYs continued to show a statistically significant linear trend with physical activity level. Similar findings were observed when the cohort was stratified by gender and BMI.

Conclusion: We found a strong graded relationship between greater physical activity and better QALYs. Moving individuals from the Inactive to Insufficiently Active group or from the Insufficiently Active to Meeting Guidelines group could be associated with a 0.08 increase in QALYs over 2 years. An intervention costing $4,000 or less that resulted in such physical activity gains would be cost effective using a $50,000 per QALY gain cutoff. Our analysis further supports the potential effectiveness and cost- effectiveness of interventions to promote physical activity even if recommended levels are not fully attained.

Disclosures: K. Sun, NoneJ. Song, NoneL. Manheim, None C. K. Kwoh, None R. W. Chang, NoneP. A. Semanik, None D. D. Dunlop, None C. Eaton, None