Socio-economic inequalities in occurrence and health care costs in rheumatic and musculoskeletal diseases: results from a Spanish population-based study including 1.9 million persons

Objective To explore and compare the impact of socio-economic deprivation on the occurrence of the major rheumatic and musculoskeletal diseases (RMDs) and health care costs. Methods Data on diagnoses, socio-demographics and health care costs of the entire adult population of the Basque Country (Spain) was used. Area deprivation index included five categories (1 to 5 (most deprived)). Cost categories included primary and specialist care, emergency room, hospitalisations, and drug prescriptions. Twenty-nine RMDs were grouped into seven groups: Rheumatoid Arthritis, Spondyloarthritis, Crystal Arthropathies, Osteoarthritis, Soft Tissue Diseases, Connective Tissue Diseases, and Vasculitis. The relations between the deprivation and the occurrence of RMD and costs were explored in regression models adjusted for relevant confounders. Results Data from 1,923,156 adults were analysed. Mean age was 49.9 (SD18.4) years, 49% were males. Soft tissue diseases were the most prevalent RMD (5.5%, n=105,656), followed by osteoarthritis (2.2%, n=41,924). Socio-economic deprivation was associated with higher likelihood to have any of the 29 RMDs. The strongest socio-economic gradient was seen for the soft tissue diseases (OR 1.82 [95% CI 1.78; 1.85], most vs. least deprived), followed by osteoarthritis (OR 1.59 [1.54; 1.64]). Deprivation was also associated with higher costs across the majority of the conditions however patterns were more blurred, and inverse relationship was observed for connective tissue diseases, gout, hip osteoarthritis and undifferentiated (poly) arthritis. Conclusion Socio-economic deprivation is associated with increased occurrence of all RMDs, and in most cases more deprived patients incur higher health care costs.