Inflammatory rheumatic diseases and the risk of drug use disorders: a register-based cohort study in Sweden

To investigate the association between chronic inflammatory rheumatic diseases (CIRD) and drug use disorder (DUD). Individuals aged ≥ 30 years in 2009 that met the following conditions were included: residing in the Skåne region, Sweden, with at least one healthcare contact in person and no history of DUD (ICD-10 codes F11-F16, F18-F19) during 1998–2009 (N = 649,891). CIRD was defined as the presence of rheumatoid arthritis (RA), ankylosing spondylitis (AS), psoriatic arthritis (PsA), or systemic lupus erythematosus. Treating CIRD as a time-varying exposure, we followed people from January 1, 2010 until a diagnosis of DUD, death, relocation outside the region, or December 31, 2019, whichever occurred first. We used flexible parametric survival models adjusted for attained age, sociodemographic characteristics, and coexisting conditions for data analysis. There were 64 (95% CI 62–66) and 104 (88–123) incident DUD per 100,000 person-years among those without and with CIRD, respectively. CIRD was associated with an increased risk of DUD in age-adjusted analysis (hazard ratio [HR] 1.77, 95% CI 1.49–2.09). Almost identical HR (1.71, 95% CI 1.45–2.03) was estimated after adjustment for sociodemographic characteristics, and it slightly attenuated when coexisting conditions were additionally accounted for (1.47, 95% CI 1.24–1.74). Fully adjusted HRs were 1.49 (1.21–1.85) for RA, 2.00 (1.38–2.90) for AS, and 1.58 (1.16–2.16) for PsA. More stringent definitions of CIRD didn’t alter our findings. CIRD was associated with an increased risk of DUD independent of sociodemographic factors and coexisting conditions.