Socioeconomic status and the risk for being diagnosed with spondyloarthritis and chronic pain: a nested case-control study

Socioeconomic status could potentially impact on which type of rheumatic diagnosis a patient receives. We determined whether different socioeconomic status is a risk factor for being diagnosed with spondyloarthritis (SpA) or chronic pain. In a nested case-control study, we identified two sets of adult cases diagnosed with (i) SpA (n = 1,194) and (ii) chronic pain (n = 3,730) during 2010-2012 in SkAyenne region, Sweden. We randomly sampled controls matched for age and sex. Level of education, marital status, and income were identified in national registers 4 years before inclusion. We also studied health-care utilization, prescribed pharmaceuticals, and work status. We used conditional logistic regressions and included socioeconomic variables and geographic area in the models. Low (odds ratio [OR] 1.69 95 % CI 1.50-1.91) or moderate education (OR 1.43 95 % CI 1.30-1.57), and low (OR 1.40 95 % CI 1.25-1.57) or moderate income (OR 1.24 95 % CI 1.10-1.38) were associated with a chronic pain diagnosis. For a SpA diagnosis, moderate income (OR 1.25 95 % CI 1.04-1.50) was the only significant factor identified. Both case groups had a larger proportion that did not work (P < 0.001), used more health care (P < 0.001), and were more frequently prescribed NSAIDs (P < 0.001) 4 years before diagnosis than controls. We confirmed that lower levels of education and income are associated with a chronic pain diagnosis. This association may reflect a true higher incidence of chronic pain and/or increased consultation propensity for such pain in people with socioeconomic status. We found no such association for SpA.