Association of functional outcome with both personal‐ and area‐level socioeconomic inequalities in patients with inflammatory polyarthritis

Objective To describe the relationship between baseline area‐ and person‐level social inequalities and functional disability at 3 years in patients with early inflammatory polyarthritis (IP). Methods A total of 1,393 patients with new‐onset IP were recruited and allocated an Index of Multiple Deprivation (IMD) 2004 score based on their area of residence, and a social class based on baseline self‐reported occupation. Differences in the Health Assessment Questionnaire (HAQ) score at baseline and 3 years by IMD or social class were tested. The mean 3‐year change in HAQ score was compared by IMD and social class, and interactions between these measures examined. Results Patients from more deprived areas had poorer 3‐year HAQ outcome than those from less deprived areas ( P = 0.019, adjusted for baseline HAQ score, age, sex, and symptom duration). The mean difference in HAQ change was most notable between the most deprived (IMD4) and least deprived areas (IMD1) (0.22; 95% confidence interval [95% CI] 0.11, 0.34). There was also a significant difference in HAQ score change between patients of the highest (SCI and II) and lowest social class (SCIV and V) (0.11; 95% CI 0.02, 0.20). For the mean (95% CI) 3‐year change in HAQ score, a significant interaction exists between IMD score and social class and their association with HAQ scores ( P = 0.001) to modify outcome: IMD1/SC I and II −0.23 (95% CI −0.40, −0.06) versus IMD 4/SC IV and V 0.15 (95% CI −0.05, 0.34). Conclusion Person‐ and area‐level inequalities combine to modify outcome for rheumatoid arthritis. A person's social circumstance and residential environment have independent effects on outcome and are not just alternative measures of the same exposure.