Nonarticular indicators were more potent signs of an individuals mobility limitations.
Potentially reversible variables, such as psychosocial factors, joint symptoms, and body composition had more impact on the walking speed of rheumatoid arthritis (RA) patients than articular characteristics, according to researchers.
According to data from 132 RA patients who undertook a timed 400-meter, long-corridor walk, several significant nonarticular indicators of a slower walking speed accounted for 60% of the observed variation in walking speed, while specific articular features, such as upper/lower extremity or large/small joint involvement, accounted for just 21% of explainable variation, reported Jon T. Giles, MD, MPH, of Columbia University in New York City, and colleagues in Arthritis Care and Research.
These variables were:
- Older age
- Higher depression scores
- Higher reported pain and fatigue
- Higher numbers of swollen and replaced joints
- Higher cumulative prednisone exposure
- Lack of treatment with disease modifying antirheumatic drugs (DMARDs)
Among articular features, slower speed was primarily related to large or medium lower-extremity joint involvement. For participants with worse body composition, having any relevant characteristic was associated with a 20% lower walking speed (P <0.001) compared with only a 6% lower speed for those with better body composition (P=0.010).
"The assumption that articular features are the largest contributor to mobility limitation in RA may be unfounded, as other characteristics such as generalized pain, depression, and fatigue are also potential contributors," the authors wrote.
Gait velocity has been previously identified as a single predictor of adverse events in healthy seniors in the general population, they explained.
The study participants, ages 45 to 84, with no reported history of cardiovascular disease were enrolled in the Evaluation of Subclinical Cardiovascular Disease and Prediction of Events in Rheumatoid Arthritis (ESCAPE RA) longitudinal cohort study.
Patients were on average white and female with a median disease duration of 12 years and few depressive symptoms. Most were seropositive for rheumatoid factor (RF) and anti-cyclic citrullinated protein (CCP) antibodies, and on average had disease activity in the low to moderate range. The vast majority (87%) were on nonbiologic DMARDs and almost half were treated with biologic DMARDs (mainly anti-TNF).
Mobile patients were asked to do 10 laps up and down a 20-meter hallway course walking quickly at a maintainable pace, while staff recorded speed in meters/second. A total of 107 patients completed the full 400 meters, and among these the average walking speed was 0.95 meters/sec . About a quarter (26%) walked at a rate of <0.8 m/sec.
Patients' self-reported disability was quantified using the Stanford Health Assessment Questionnaire, the physical function domain of the Short Form 36 Health Survey, and the Valued Life Activities Questionnaire.
Other evaluations included a 44-joint articular assessment, the three-item Disease Activity Score in 28 joints with C-reactive protein (CRP), radiographs of hands and feet, current medications, depressive symptoms, fatigue, pain, chest tomography for interstitial lung disease, body mass index, and measurement of adipose and muscle tissue in the abdomen and thighs. Laboratory tests measured levels of inflammatory markers such as RF, CRP, anti-CCP, and interleukin 6.
The largest single negative indicator of walking speed was higher age, which accounted for 27% of explainable variability. The next strongest indicator was articular signs, with replaced joints accounting for double the explainable variability of swollen joints (8.7% versus 4.4%). Sex, interstitial lung disease, RA duration, autoantibody status, inflammatory markers, and radiographic scores did not independently associate with gait velocity.
The only positive indicator studied was better body composition -- in those with more lean muscle mass and density, the association of articular features with performance measures was minimal.
"Better body composition negated much of the detrimental impact of symptomatic joints on physical impairment," the authors wrote. "Lifestyle modifications to optimize body composition may be an important adjunct to intensive medical management with DMARDs, as recent investigations have shown that through structured physical training RA patients are able to alter body composition, decrease disability, and improve physical performance."
The study had some limitations including the use of a body composition propensity score, which may not have reflected individual body composition elements. The latter could be used to identify particular targets for intervention, the authors stated. They added that "investigation into the correlation between individual body composition parameters and performance is currently underway."
The study was supported by grants from the NIH/National Institute of Arthritis and Musculoskeletal and Skin Diseases and the Johns Hopkins Bayview Medical Center General Clinical Research Center.Giles disclosed a grant from the NIH/National Institute of Arthritis and Musculoskeletal and Skin Disease.
The authors disclosed no relevant relationships with industry.