Rheumatic and Musculoskeletal Diseases and Risk of Dementia: A Nested Case-Control Study

Objective: To investigate the associations between rheumatic and musculoskeletal diseases (RMDs) and incident dementia using population register-based data. Methods: This nested case-control study was conducted based on a cohort of residents in the Skåne region, Sweden, aged 50 years and older in 2009 without doctor-diagnosed dementia during 1998 to 2009 (n = 402,825). Individuals with a new main diagnosis of dementia during 2010 to 2019 were identified as incident patients with dementia (n = 22,131). Controls without diagnosed dementia were randomly matched 1:1 by sex, age, and Elixhauser comorbidity index using incidence density sampling. Separate conditional logistic regression analyses adjusted for confounders were fitted for the following RMDs, diagnosed at least 2 years before dementia diagnosis as exposure: gout, osteoarthritis, rheumatoid arthritis, spondyloarthropathies (SpA), and systemic connective tissue disorders. Subgroup analyses by dementia subtype, sex, age, comorbidity, and RMDs/dementia identification were conducted. Results: Although gout (adjusted rate ratio 0.88; 95% confidence interval 0.79–0.97), osteoarthritis (0.92; 0.88–0.96), and systemic connective tissue disorders (0.91; 0.83–0.99) were associated with decreased risk of dementia, the associations for rheumatoid arthritis (1.05; 0.92–1.19) and SpA (1.17; 0.94–1.45) were inconclusive. The associations between RMDs and incident dementia were similar across sex, age, and comorbidity subgroups with a few exceptions (eg, an adjusted rate ratio of 0.99 [95% confidence interval 0.71–1.39] in males vs 1.31 [0.99–1.74] in female patients for SpA). Conclusion: Persons with diagnosed RMDs seem to have comparable or slightly lower risks of developing dementia compared with those without known RMD.