Carpal Tunnel Syndrome (CTS) is an Early Underrecognized Feature of Rheumatoid Arthritis (RA): A Population-Based Study of CTS Occurrence Before and After RA Incidence.

Objective: We aimed to assess the occurrence of Carpal Tunnel Syndrome (CTS) before and after rheumatoid arthritis (RA) incidence and by serological status.

Methods: This population-based study included residents of a geographically defined area meeting the 1987 ACR classification criteria for RA in 1980-2019, matched 1:1 with non-RA individuals. At least two diagnosis codes ≥ 30 days apart were used to identify CTS. Cumulative incidence of CTS adjusting for competing risk of death was assessed. Logistic regression and Cox proportional hazard models were used, adjusting for age, sex, calendar year, smoking, obesity, diabetes, and hypothyroidism.

Results: We included 1335 patients with RA and 1331 individuals without RA. The overall prevalence of CTS prior to or on RA incidence/index was 179 (13%) and 85 (6%), respectively: OR 2.23; 95% CI 1.69-2.94. Most prior incidence of CTS occurred ≥ 2 years prior to index date (112 and 75 events, respectively). Following RA incidence/index, individuals with RA (versus without RA) had ~80%-higher risk of CTS (HR 1.78; 95%CI 1.38-2.30). The risk estimates of CTS in patients with seronegative (vs seropositive) RA were OR 1.33; 95%CI 0.96-1.84 prior to RA incidence and HR: 1.37, 95%CI 0.99-1.88 after RA incidence. In RA, obesity (HR 1.42, 95% CI 1.02-1.99) and seronegative CCP-antibody status (HR 1.79, 95% CI 1.07-2.99), but not other risk factors, were associated with increased CTS risk.

Conclusion: We found an over 2-fold increase in risk of CTS in years preceding RA, and 1.8-fold increased risk of incident CTS following RA onset.