Background/Purpose: Osteoarthritis (OA) is the number one chronic condition of the joints. Social determinants associated with disability progression due to OA are largely unknown. Efforts to determine if socioeconomic status (SES) is associated with OA disability progression may aid in prevention efforts. This study aims to describe the relationship between SES measures with disability progression among individuals with radiographic knee and/or hip OA from the Johnston County OA (JoCo OA) Project in rural North Carolina.

Methods: We examined the association between disability progression and each of four individual SES variables (education, occupation, income, and home ownership) and one community level SES measure (household (HH) poverty) using data from 541 participants in the JoCo OA cohort. In the time to event analysis, disability progression was defined as a change of ≥ 0.22 points in the Health Assessment Questionnaire (HAQ) disability score between baseline and last follow-up. Risk of disability progression was evaluated using a parametric time to event Weibull model that accounted for interval censoring. Change in HAQ score was assessed using linear mixed models (LMM). Interaction terms were included to examine disability progression by age. All analyses simultaneously adjusted for other SES measures, as well as age, race, and gender.

Results: Based on the time to event analysis, individuals who reported making ≤ $30,000 were more likely to experience disability progression compared to those with an income > $30,000 (aHR = 1.45; 95% CI: 1.03, 2.04). In contrast, the LMM analysis showed that lack of home ownership was the only SES covariate that had an independent association with disability after accounting for interaction terms (β: 0.14; 95% CI: 0.02, 0.25). Additionally, the interaction between age and HH poverty indicated that as an individual aged, the effect of a 10% increase in HH poverty on increases in HAQ scores was greater (β = 0.03; 95% CI: 0.01, 0.05). This suggests an increased risk of disability progression among individuals living in areas of higher HH poverty as they age.

Conclusion: Lower income, lack of home ownership and increased household poverty are independently associated with increased risk of disability progression, suggesting that societal interventions to address these specific SES factors could help to mitigate OA-related disability.