Background/Purpose: Physical activity in RA patients is significantly less than in counterparts without RA, and many live just above the muscle strength threshold needed for activities of daily living. It is not known whether physical activity declines prior to the onset of RA, potentially because of joint swelling and tenderness or because of the inflammatory processes associated with preclinical autoimmunity. Therefore, we first sought to determine whether RA-related autoantibodies, and joint tenderness and swelling, were associated with physical activity in first-degree relatives (FDRs) of RA patients, a population at increased risk for future RA.

Methods: In the Studies of the Etiology of RA (SERA) (a multicenter prospective study of preclinical RA), we evaluated associations between RA-related autoantibodies (Abs), swollen and tender joint count (SJC, TJC) and hours of physical activity in 233 FDRs. We defined RA-related autoantibody positivity as being positive (+) for any of 5 RA-related Abs: rheumatoid factor (RF), RF isotypes – IgM, IgG, IgA, or anti-cyclic citrullinated peptide (anti-CCP2). Positivity for a High-Risk Profile (HRP) was defined as being (+) for anti-CCP2 and/or 2 or more RF isotypes (IgM, IgG, IgA), which has been shown to be 96% specific for future RA. Hours sleeping, sitting, and engaging in slight, moderate, or heavy activity during a typical 24-hour day were obtained through questionnaire, weighted to reflect metabolic expenditure, and calculated as follows: PA score = (1.0*h_sleep + 1.1*h_sedentary + 1.5*h_slight + 2.4*h_moderate + 5.0*h_heavy). ANCOVA was used to evaluate associations between continuous PA score and Ab and HRP positivity, adjusting for age, sex, race, body mass index (BMI), smoking, and TJC. These same methods were used to evaluate associations between SJC and TJC and PA score. Logistic regression was used to evaluate associations between the dichotomous median-and-above (versus < median) PA score and Ab and HRP positivity adjusted for these same covariates.

Results:

Mean age was 47±17 years. 70% were female, 67% were White, 25% were Ab+, and 7% were HRP(+). Mean SJC was 0.3±1 and mean TJC was 1±2 for all FDRs. Average PA score was 37.4. Neither Ab(+) status nor HRP(+) status were associated with PA score or median-and-above PA score in fully adjusted analysis (PA Score: β_Ab(+)=0.20±1.3, p=88; β_HRP(+)=-0.27±0.6, p=0.66) (Median-and-above PA Score Odds Ratios (ORs): OR_Ab(+)=1.33, 95% CI=0.67-2.67; OR_HRP(+)=0.43, 95% CI=0.14-1.30)

Neither SJC nor TJC were significantly associated with PA score in fully adjusted analysis (PA Score: β_SJC= -0.54±0.6, p=0.38 β_TJC= 0.03±0.3, p=0.91).

Conclusion:

In FDRs of RA patients, neither the number of swollen and tender joints nor autoantibody status was associated with physical activity in cross-sectional analysis.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/associations-between-rheumatoid-arthritis-ra-related-autoimmunity-joint-symptoms-and-physical-activity-in-first-degree-relatives-without-ra-in-a-prospective-cohort/