What is the relationship between rheumatoid arthritis, multimorbidity and adverse health-related outcomes?

Problem

Rheumatoid arthritis (RA) is a common autoimmune inflammatory arthropathy. Multimorbidity (the co-existence of ≥2 long-term health conditions (LTCs)) is highly prevalent in people with RA however, most research to date has generally focussed on RA and comorbidity (1 other LTC) rather than multimorbidity. This work aims to explore the existing literature to determine what is known about the effect, if any, of multimorbidity on mortality and other health-related outcomes (physical functioning/well-being) in people with RA.

Approach

A systematic review was conducted following PRISMA guidelines. Six electronic medical databases were searched: CINAHL, Cochrane Library, Embase, Medline, PsycINFO and Scopus, using a comprehensive search strategy. Studies were screened by two reviewers to identify longitudinal observational studies with extractable data relating to multimorbidity and our outcomes of interest in adults with RA. Studies were restricted to English language, full-text articles. Quality appraisal was undertaken by two independent reviewers using the Cochrane-developed, QUIPS tool, and a narrative synthesis conducted.

Findings

In total, 4,772 papers were identified by the search strategy, with 15 studies fulfilling the criteria for inclusion in our review. Of these, 6 studies had all-cause mortality as an outcome, 8 studies reported on a relevant health-related outcome and 1 study reported on both. The number of participants ranged from 183 to 18,485 across studies and all studies were conducted in developed countries with high-income economies between 1985-2014 with follow-up periods ranging from 6 months to 23 years. The mean age of participants ranged from 53.5 to 66.6 years old with the percentage of females between 60.0-84.2% across studies. Six studies reported a significant association between multimorbidity and increased risk of all-cause mortality in people with RA, using Cox proportional hazard models and Kaplan-Meier survival estimates. While 9 studies reported significant associations between multimorbidity and reduced functional status (measured by the Health Assessment Questionnaire (HAQ)) in people with RA. Three of these studies also reported a further significant association between reduced quality of life and multimorbidity in people with RA.

Consequences

Multimorbidity in people with RA is a significant predictor for increased mortality and poorer health-related outcomes. Multimorbidity should therefore be taken into consideration when managing RA, with further research required in this area to guide future health service design and guidelines.