Influence of national socioeconomic status on treatment retention and disease activity in psoriatic arthritis and axial spondyloarthritis: evidence over 2 years in 13 European countries

OBJECTIVES: To explore the association between national socioeconomic indicators, and (i) 6/12/24-month retention of biologic/targeted synthetic disease-modifying antirheumatic drugs (b/tsDMARD), and (ii) disease activity at treatment start, in patients with psoriatic arthritis (PsA) or axial spondyloarthritis (axSpA). METHODS: Longitudinal data from 13 European countries, including 38,911 patients with spondyloarthritis (17,296 PsA and 21,615 axSpA) initiating b/tsDMARDs in 2015-2021, were collected by the European Spondyloarthritis Research Collaboration Network. Kaplan-Meier, mixed-effects Cox regression, linear regression, and mixed models were used for comparisons across countries with low/medium/high national socioeconomic indicators (gross domestic product [GDP], Human Development Index [HDI], gross national income, current health expenditure, out-of-pocket expenditure), stratified by disease/b/tsDMARD number/sex. RESULTS: Drug retention was significantly lower in both men and women with PsA/axSpA from countries with high vs medium/low GDP per capita after 6/12/24 months' treatment with 1st/≥2nd b/tsDMARD (log rank P < .001). For all socioeconomic indicators, higher wealth was associated with earlier discontinuation of 1st b/tsDMARD both in PsA and axSpA men and women. The strength of associations varied across indicators, treatment lines, and sex. The strongest associations between socioeconomic measures and b/tsDMARD retention were seen with GDP per capita and HDI, and most prominently in women with axSpA. At the country level, most disease activity measures at the start of 1st/≥2nd b/tsDMARD were significantly worse with lower GDP, particularly for PsA. CONCLUSIONS: Treatment retention varies with countries' socioeconomic status. Clinicians and health policy makers should be aware of later discontinuation/switching of b/tsDMARDs and a tendency to higher country-level disease activity at b/tsDMARD initiation in lower-income countries.