Newswise — Weight loss may be more effective than weight maintenance in reducing knee osteoarthritis, according to research presented this week at the American College of Rheumatology Annual Scientific Meeting in Philadelphia, Pa.
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 slippery 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.
Most commonly affected are the weight-bearing joints—the knees, hips and spine. Osteoarthritis in the knee and hip areas can generate chronic pain or discomfort during standing or walking. Deterioration of disks between spine vertebrae can cause back and neck stiffness and pain. And men and women are equally affected.
On average, adults gain weight throughout most of their life span. Weight loss is difficult to achieve, and it is possible that weight maintenance is a more attainable goal for some people. Researchers recently studied 1,480 people who were a part of the Johnston County Osteoarthritis Project (a study of Caucasian and African American residents of Johnston County, NC who were at least 45 years old) to determine if weight maintenance would reduce the risk of radiographic knee osteoarthritis, which is osteoarthritis that has been confirmed by an X-ray.
The researchers defined weight change as any change from initial weight and placed it into several different categories – ranging from greater or equal to five percent weight loss to greater or equal to five percent weight gain.
Of the 1,480 participants, 63.2 percent were female and 25.9 percent were African American with an average age of 59.4 and an average BMI of 28.6. At an average follow-up time of 5.9 years, osteoarthritis had developed in 415 of 2,788 knees (some individuals only had one of their knees examined for the study).
When compared to participants who had gained weight (which was 31.4 percent of the group), those who maintained weight (32.8 percent) were no less likely to develop knee OA, but those who had lost weight (16.7 percent) had reduced their overall risk.
“Among men and women aged 45 years or older, we estimated a reduction in the six-year risk of radiographic knee osteoarthritis from about 19 percent in those who gained or maintained their weight to about 14 percent in those who lost weight,” explains Lauren M. Abbate, MSPH, doctoral student, department of epidemiology, Thurston Arthritis Research Center, University of North Carolina, Chapel Hill, N.C., and lead investigator in the study.
“The estimated absolute risk reduction of approximately five percent corresponds to about one fewer new case of radiographic knee osteoarthritis over six years for every 20 people who lose weight. Obesity is a very strong risk factor for radiographic knee osteoarthritis, and these findings emphasize how critical weight loss is in the quest to decrease the risk of developing knee osteoarthritis.”
The ACR is an organization of and for physicians, health professionals, and scientists that advances rheumatology through programs of education, research, advocacy and practice support that foster excellence in the care of people with or at risk for arthritis and rheumatic and musculoskeletal diseases. For more information on the ACR’s annual meeting, see www.rheumatology.org/annual.
Editor’s Notes: Ms. Abbate will present this research during the ACR Annual Scientific Meeting at the Pennsylvania Convention Center at 4:30 PM on Sunday, October 18 in Room 108 B. Ms. Abbate will be available for media questions and briefing at 1:30 PM on Monday, October 19 in the on-site press conference room, 109 A.
Presentation Number: 629
The Relationship Between Weight Maintenance and Incident Radiographic Knee Osteoarthritis: The Johnston County Osteoarthritis Project
Lauren M. Abbate, MSPH, Epidemiology, The University of North Carolina, Chapel Hill, NC June Stevens, PhD, Nutrition, The University of North Carolina, Chapel Hill, NC Todd A. Schwartz, DrPH, Biostatistics, The University of North Carolina, Chapel Hill, NC Leigh F. Callahan, PhD , Thurston Arthritis Research Center, The University of North Carolina, Chapel Hill, NC Jordan B. Renner, MD, Radiology, The University of North Carolina, Chapel Hill, NC Charles G. Helmick, MD, Centers for Disease Control and Prevention, Atlanta, GA Joanne M. Jordan, MD, MPH , Thurston Arthritis Research Center, The University of North Carolina, Chapel Hill, NC
Purpose: On average, adults gain weight throughout most of their life span. Weight loss is difficult to achieve, and it is possible that weight maintenance is a more attainable goal for some individuals. The purpose of this study is to determine if weight maintenance is an effective strategy to reduce the risk of incident radiographic knee osteoarthritis (rKOA).
Methods: Data were from the Johnston County Osteoarthritis Project, a longitudinal study of African-Americans and Whites aged 45 years and older in Johnston County, NC from T0 (1990-1998) to T1 (1999- 2003 (n=1,480). Weight change was defined as change from initial weight and was coded as a 5-level variable with categories defined as: ≥5% loss, >3 to <5% loss, ± 3%, >3 to <5% gain, and ≥5% gain. Indicator variables were used to make contrasts between ≥5% loss (weight loss), ± 3% (weight maintenance), and ≥5% (weight gain) with weight gain as the referent. Incident rKOA was defined as Kellgren-Lawrence (K-L) grade of 0 or 1 at T0 and K-L ≥ 2 at T1. Knee-based Weibull proportional hazards models with adjustment for the correlation between knees were used to calculate hazard ratios and 95% confidence intervals for the association between weight change incident rKOA. All models were adjusted for age, race, sex, height, and the mean of weights from T0 and T1.
Results: Of the 1,480 individuals, 63.2% were female and 25.9% were African-American with mean (SD) age and BMI of 59.4 (9.4) years and 28.6 (5.5) kg/m2, respectively. Mean (SD) follow-up time was 5.9 (1.3) years (range 3.6 to 13.2), during which rKOA developed in 415 (14.9%) of 2,788 knees. Compared to those who gained weight (31.4%), those who maintained weight (32.8%) were no less likely to develop incident rKOA [HR=1.02 (95% CI=0.77, 1.35)], but those who lost weight (16.7%) were at reduced risk [0.71 (0.49, 1.01)].
Conclusion: Weight loss, but not weight maintenance, may be an effective strategy to reduce the risk of incident rKOA.
Disclosure: L. M. Abbate, None; J. Stevens, None; T. A. Schwartz, None; L. F. Callahan, None; J. B. Renner, None; C. G. Helmick, None; J. M. Jordan, None.
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