To assess the influence of income on self-reported disease and work productivity outcomes.
Persons with rheumatoid arthritis (RA) diagnosis (International Classification of Diseases, 10th ed. codes M05/M06) on health insurance claims data in at least 2 quarters of 2013 were randomly selected. They were mailed questionnaires covering RA diagnosis, household income, functional capacity [Hannover functional status questionnaire (FFbH), 0-100], RA Impact of Disease questionnaire (RAID; 0-10), self-reported swollen joint count (SJC; 0-48), tender joint count (TJC; 0-50), and effect of RA on work productivity (change of work, fewer working hours, sick leave, application for disability pension, and others). Weighted multivariable linear regression models were used to assess the association between income and disease outcomes.
A total of 1492 persons of working age who confirmed RA diagnosis were available for analysis. The mean age was 55 years, 82% were women, and 74% were under rheumatologic care. A total of 27%, 52%, and 21% had a low (< €1500), medium (€1500-3200), and high monthly income (> €3200), respectively. Respondents with low income had the worst mean FFbH, RAID, SJC, and TJC values. This was confirmed in the regression model: mean FFbH low versus high income -8.65 (95% CI -9.72 to -7.58), RAID 0.73 (0.59-0.86), and SJC 3.47 (2.86-4.08). Sick leave (8.7%/3.5%/1.8%) and disability pension (18.1%/9.6%/6.9%) were more frequent in patients with low versus medium versus high income (p < 0.05).
The association of low income with a higher disease burden, more functional disability, and higher rates of work loss emphasizes the need to focus on these outcomes when choosing treatment strategies for patients in the lower income groups.