How do multiple long-term conditions impact on the cost-of-illness in early rheumatoid arthritis?

Objective Multiple long-term conditions (MLTCs) are prevalent in rheumatoid arthritis (RA) and associated with worse outcomes and greater economic burden. However, little is known about the impact of MLTCs on the cost-of-illness (COI) in early RA, including direct and indirect costs. The objective of this study was to quantify this impact on COI. Methods The Scottish Early Rheumatoid Arthritis study is a national cohort of adults with new-onset RA. Direct costs were estimated applying relevant unit costs to health resource utilisation; indirect costs were measured by productivity loss due to health conditions. Two-part models were used, adjusting for age, gender, baseline functional disability and health-related quality of life. The Charlson Comorbidity Index score was calculated using ICD-10 diagnoses. Individuals were defined as 'RA alone', 'RA plus LTC' and 'RA plus MLTCs' according to the number of coexisting LTCs. Results Data were available for 818 participants. Average annualised direct costs incurred by people with early RA plus MLTCs (4444; pound 95% CI 3100 pound to 6371) pound were twice as, and almost five times higher than, those with a single LTC (2184; pound 95% CI 1596 pound to 2997) pound and those without LTC (919; pound 95% CI 694 pound to 1218) pound, respectively. Indirect costs incurred by RA plus MLTCs (842; pound 95% CI 377to pound 1521) pound were 3.1 times higher than RA alone (530; pound 95% CI 273to pound 854) pound. The relative proportion of direct costs increased with LTC category, ranging from 77.2% to 84.1%. In addition to increased costs with LTCs, costs also increased with age and were higher for men regardless of LTC category. Conclusions MLTCs impact on COI early in the course of RA. The presence of LTCs is associated with significant increases in both direct and indirect costs among people with early RA.