Background/Purpose: Patients with RA have an increased burden of multimorbidity. Although many comorbidities vary by sex, sex differences in multimorbidity among individuals with RA have not been examined. We aimed to compare multimorbidity between women and men with RA and comparators without RA.

Methods: We used a longitudinal, real-world database with de-identified administrative claims for commercial and Medicare Advantage enrollees to identify cases of RA and matched controls. Cases were defined as patients aged ≥18 years with ≥2 diagnoses of RA in January 1, 2010 – June 30, 2019 and ≥1 prescription fill for a DMARD any time after the first RA diagnosis. Controls were persons without RA matched 1:1 to RA cases on age, sex, census region, calendar year of index date (corresponding to the date of second diagnosis code for RA), and length of prior medical/pharmacy coverage. Race was classified as non-Hispanic White (White), non-Hispanic Black (Black), Asian, Hispanic, or other/unknown, based on self-report or derived rule sets. Multimorbidity (2 or more comorbidities, MM2+) and substantial multimorbidity (5 or more comorbidities, MM5+) were defined using 44 preidentified chronic comorbidities (England et al. ARD 2020) assessed during the year prior to index date. Logistic regression models were used to estimate odds ratios (OR) with 95% confidence intervals (CI).

Results: The study included 155,631 cases with RA and 155,631 matched non-RA comparators (mean age 59.6 years, 76.0% female for both cohorts). In both cohorts, women were slightly younger (mean age 60.0 vs. 62.0 years). Among RA patients, women were more racially/ethnically diverse than men, with 70% of women (76% men) being White, 11% (9%) Hispanic, 11% (7%) Black, 3% (2%) Asian, and 6% (6%) other/unknown. Racial/ethnic diversity was more similar among non-RA women and men with 72% women (74% men) being White, 9% (9%) Hispanic, 10% (8%) Black, 3% (4%) Asian, and 6% (6%) other/unknown. Overall, patients with RA had more MM2+ than non-RA subjects (69.9% vs 53.5%), and more MM5+ than non-RA subjects (30.5% vs 18.2%).

Observed rates of MM5+ were similar in women and men without RA (18.1% vs 18.5%, p=0.09), but among RA patients, women had higher observed rates of MM5+ than men (30.9% vs 29.0%, p< 0.0001). This pattern persisted following adjustment for age, race/ethnicity, and geographic region, showing increased rates of MM5+ among RA women versus men (OR: 1.18; 95% CI: 1.16-1.22) and similar rates among non-RA women and men (OR: 1.04; 95% CI: 1.00-1.08). Examination of individual comorbidities showed that women with RA had more depression, hypothyroidism, fibromyalgia, chronic back pain, asthma, gastroesophageal reflux disease, osteoarthritis, and osteoporosis compared to men with RA and women without RA.

Conclusion: This large nationwide study showed increased occurrence of multimorbidity in women with RA compared to men with RA, while women and men without RA had similar levels of multimorbidity, even after adjustment for age, race/ethnicity, and geographic region. The underlying mechanisms for these sex differences require further investigation.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/women-with-rheumatoid-arthritis-have-more-multimorbidity-than-men-in-a-large-nationwide-us-study/