Disparities in multimorbidity and comorbidities in rheumatoid arthritis by sex acrossthe lifespan

Multimorbidity is burdensome for people with rheumatoid arthritis (RA). We investigated differences in multimorbidity and comorbidities by sex and age in the RA population.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.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.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.