Combined effect of individual and neighbourhood socioeconomic status on mortality of rheumatoid arthritis patients under universal health care coverage system

Background. The National Health Insurance program in Taiwan is a public insurance system for the entire population of Taiwan initiated since March 1995. However, the association of socioeconomic status (SES) and prognosis of rheumatoid arthritis (RA) patients under this program has not been identified. Objectives. Using the National Health Insurance Research Database in Taiwan, we aimed to examine the combined effect of individual and neighbourhood SES on the mortality rates of RA patients under a universal health care coverage system. Measures. A study population included patients with RA from 2004 to 2008. The primary end point was the 5-year overall mortality rate. Individual SES was categorized into low, moderate and high levels based on the income-related insurance payment amount. Neighbourhood SES was defined by household income and neighbourhoods were grouped as an 'advantaged' area or a 'disadvantaged' area. The Cox proportional hazards regression model was used to compare outcomes between different SES categories. A two-sided P value < 0.05 was considered statistically significant. Results. Medical data of 23 900 RA patients from 2004 to 2008 were reviewed. Analysis of the combined effect of individual SES and neighbourhood SES revealed that 5-year mortality rates were worse among RA patients with a low individual SES compared to those with a high SES (P < 0.001). In the Cox proportional hazards regression model, RA patients with low individual SES in disadvantaged neighbourhoods incurred the highest risk of mortality (Hazard ratio = 1.64; 95% confidence interval, 1.26-2.13, P < 0.001). Conclusions. RA patients with a low SES have a higher overall mortality rate than those with a higher SES, even with a universal health care system. It is crucial that more public policy and health care efforts be put into alleviating the health disadvantages, besides providing treatment payment coverage.