Background/Purpose: Osteoporosis, defined by Tscore < -2.5, is one of the main consequences of RA and it appears early in the disease. It is twice as prevalent in RA as it is in the general population; and low bone mineral density (BMD) in RA is associated with increased risk of hip and vertebral fractures. It is not known exactly whether this degeneration begins in pre-clinical RA and whether joint symptoms provide clinicians insight into these degenerative changes, especially in the spine. Therefore, we investigated associations between RA-specific joint symptoms and thoracic BMD in a community-based cohort free of RA.

Methods: We evaluated associations between presence of RA-specific joint symptoms and thoracic BMD (tBMD) using computed tomography (CT) in 31 individuals from the Studies of the Etiology of RA who were RA-free based on the 1987 ACR and 2010 ACR/EULAR criteria for RA. A physician confirmed joint swelling; participants self-reported stiffness and pain in the wrist, elbow, or any metacarpophalangeal, proximal interphalangeal, or metatarsophalangeal joints. Thoracic BMD on CT was measured using OsiriX 7.5 (Pixmeo, Geneva, Switzerland), and calculated using average BMD of T7-T9 vertebrae. Sex-specific Tscores were calculated as follows: T(_female) = (BMD(_{individual mean}) – 222)/36; T(_male) = (BMD(_{individual mean}) – 215)/33; where < -2.5 is considered osteoporosis and < -1.0 is considered osteopenia. Associations between joint symptoms and tBMD were evaluated using ANCOVA and adjusted for age, race, body mass index (BMI), pack-years smoking, high sensitivity c-reactive protein (CRP), number of autoantibodies (Anti-CCP, RF-IgG, RF-IgM, RF-IgA), and the source of their recruitment into SERA (as a first degree relative or health fair participant).

Results: Among 31 SERA participants, average(SD) age was 54(13), BMI was 27(5), CRP was 3(4), Tscore was -1(2), 45% were women, 94% were non-Hispanic White, and everyone had an average of 1(1) autoantibody. Joint swelling was associated with lower Tscores, although the association was marginally significant (p=0.08). Neither joint stiffness nor pain was associated with Tscores (Table).

Conclusion: In a cohort of RA-free individuals, neither joint swelling, stiffness, nor pain was significantly associated with tBMD Tscores. These preliminary data were limited by small sample size. Joint swelling was marginally associated with tBMD, thus future research with larger sample size is required to determine whether joint swelling may be linked to bone density.