Disparities in multimorbidity and comorbidities in rheumatoid arthritis by sex across the lifespan.

Objectives: Multimorbidity is burdensome for people with RA. We investigated differences in multimorbidity and comorbidities by sex and age in the RA population.

Methods: This cross-sectional analysis used national administrative claims (OptumLabs® Data Warehouse) from people with RA and non-RA comparators (matched on age, sex, race, census region, index year and length of baseline insurance coverage) from 2010-2019. RA was determined using a validated algorithm. Multimorbidity was defined as ≥2 (MM2+) or ≥5 (MM5+) comorbidities from a validated set of 44 chronic conditions. We used logistic regression to assess associations between characteristics and multimorbidity.

Results: The sample included 154 391 RA patients and 154 391 non-RA comparators. For people aged 18-50 years, RA women (vs RA men) had 7.5 and 4.4 (vs 3.2 and 0.9 in non-RA women vs non-RA men) percentage point increases for MM2+ and MM5+, respectively. For people aged 51+ years, RA women (vs RA men) had 2.1 and 2.5 (vs 1.2 and 0.3 in non-RA women vs non-RA men) percentage point increases for MM2+ and MM5+, respectively. Interactions revealed that differences in multimorbidity between women and men were exacerbated by RA (vs non-RA) (P < 0.05), with more pronounced effects in people aged 18-50. Men had more cardiovascular-related conditions, whereas RA women had more psychological, neurological and general musculoskeletal conditions. Other comorbidities varied by sex and age.

Conclusion: Multimorbidity disproportionately impacts women with RA. Research, clinical and policy agendas for rheumatic diseases should acknowledge and support the variation in care needs by sex and gender across the lifespan.