OBJECTIVE: To determine whether unique multimorbidity patterns are associated with long-term rheumatoid arthritis (RA) disease severity. METHODS: We conducted a cohort study within the Veterans Affairs Rheumatoid Arthritis registry. We applied previously derived multimorbidity patterns based on the presence of diagnostic codes for relevant conditions prior to enrollment using linked administrative data. Disease activity and functional status were assessed longitudinally up to 5 years after enrollment. The association of multimorbidity patterns with disease activity and functional status were assessed using generalized estimating equations models adjusting for relevant confounders. RESULTS: We studied 2,956 participants, of which 88.2% were male, 76.9% reported white race, and 79.3% had a smoking history. Mental health and substance abuse (ß 0.12 [95% confidence interval {CI} 0.00, 0.23]), cardiovascular (ß 0.25 [95% CI 0.12, 0.38]), and chronic pain (ß 0.21 [95% CI 0.11, 0.31]) multimorbidity were associated with higher Disease Activity Score in 28 joints (DAS28) scores. Mental health and substance abuse (ß 0.09 [0.03, 0.15]), cardiovascular (ß 0.11 [95% CI 0.04, 0.17]), and chronic pain multimorbidity (ß 0.15 [95% CI 0.10, 0.20]) were also associated with higher Multidimensional Health Assessment Questionnaire (MDHAQ) scores. The metabolic pattern of multimorbidity was not associated with DAS28 or MDHAQ. The number of multimorbidity patterns present was highly associated with DAS28 and MDHAQ (P trend < 0.001), and patients with all four multimorbidity patterns had the highest DAS28 (ß 0.59 [95% CI 0.36, 0.83]) and MDHAQ (ß 0.27 [95% CI 0.16, 0.39]) scores. CONCLUSION: Mental health and substance abuse, chronic pain, and cardiovascular multimorbidity patterns are associated with increased RA disease activity and poorer functional status. Identifying and addressing these multimorbidity patterns may facilitate achieving RA treatment targets.
