Household Income and Quality of Life in Patients with Rheumatoid Arthritis: Results from a Mestizo Population with Full Health-Care Coverage

Objective: Socioeconomic status (SES) is strongly associated with self-reported outcomes in the general population, but there is little information in patients with rheumatoid arthritis (RA). There are several indicators of socioeconomic status and one such an indicator is household income. We set out a study to test the hypothesis that household income is associated with quality of life independently of demographic and disease related variables in a population of Mestizo patients with RA who have full health-care coverage.
Methods: One hundred and eighty one Mestizo patients with RA and full health-care coverage underwent an interview, physical exam, and all their clinical charts were reviewed. Based on their monthly -US dollar equivalent- household income (MHI), patients were classified in the following categories: very low SES (MHI: <$160), low SES (MHI: $160-$318), moderate-high SES (MHI >$318). Quality of life was quantified with the Medical Outcomes Study Short Form 36 (SF-36). Data obtained included demographic variables (age, sex, and education), DAS28, MHAQ, comorbidities, fatigue, and disease duration. The association between socioeconomic status and quality of life was examined with Kruskal Wallis test and adjustment for potential confounders, selected a priori, was performed with the use of multiple lineal regression models.
Results: Patients with RA had a mean age of 58+/-13 years and 85.6% were female. Their mean DAS28 was 4.8+/-1.6 and their mean number of years of education was 10.8+/-4.7. Fifty-four (29.8%) had very low, 70 (38.7%) had low, and 57 patients (31.5%) had moderate-high SES. Lower health related quality of life was associated with lower household income as shown by the following SF-36 results: patients with very low SES (30.4+/-16.1), patients with low SES (37.5+/-20.5), and patients with moderate-high SES (44.8+/-23.0), P= 0.003. The association between socioeconomic status and impaired quality of life remained significant after adjustment for age, sex, and years of education (Coef=7.6, P<0.001) but was attenuated after further adjustment for disease activity, MHAQ, comorbidities, fatigue, and disease duration (Coef=2.5, P=0.077).
Conclusion: Lower socioeconomic status is associated with impaired quality of life independent of demographic variables in Mestizo patients with rheumatoid arthritis and full health-care coverage.

 A. Garcia-Poma, None; M.I. Segami, None; H.N. Terrazas, None; C.P. Chung, None.