Carpal Tunnel Syndrome as an Early Underrecognized Feature of Rheumatoid Arthritis: A Population-Based Study of Carpal Tunnel Syndrome Occurrence Before and After Rheumatoid Arthritis Incidence.

Objective: We aimed to assess the occurrence of carpal tunnel syndrome (CTS) before and after rheumatoid arthritis (RA) incidence and by serologic status.

Methods: This population-based study included residents of a geographically defined area meeting the 1987 American College of Rheumatology classification criteria for RA in 1980 to 2019 matched 1:1 with individuals without RA. 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 mellitus, and hypothyroidism.

Results: We included 1,335 patients with RA and 1,331 individuals without RA. The overall prevalence of CTS before or on RA incidence or index was 179 patients with RA (13%) and 85 individuals without RA (6%), respectively (odds ratio [OR] 2.23; 95% confidence interval [CI] 1.69-2.94). Most previous incidences of CTS occurred ≥2 years before the index date (112 events in patients with RA and 75 events in individuals without RA, respectively). Following RA incidence or index, individuals with RA (vs those without RA) had ~80%-higher risk of CTS (hazard ratio [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) before 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 cyclic citrullinated peptide 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 a more than two-fold increase in risk of CTS in the years preceding RA and a 1.8-fold increased risk of incident CTS following RA onset.