Measurement and decomposition of socioeconomic inequality in functional disability among adults aged ≥45: Evidence from the China Health and Retirement Longitudinal Study

Abstract Objective The concurrent process of population aging and rapid economic development in China has generated a heightened interest in the health inequalities experienced by middle-aged and older adults. This study aims to quantify the trends of socioeconomic inequality for functional disability and unraveled the underlying contributors. Study Design A cross-sectional design based on four distinct years (2011 to 2018) was utilized. Methods Data were extracted from the China Health and Retirement Longitudinal Study (CHARLS), encompassing a total of 66,988 participants aged ≥45 years. Socioeconomic status (SES) was assessed based on wealth variables. The SES inequality was quantified using concentration indices. Decomposition method was employed to disentangle the contributions to inequality. Results The prevalence of functional disability among adults aged ≥45 years increased from 14.9% (95% CI: 14.4 to 15.5) in 2011 to 16.4% (95% CI: 15.8 to 17.0) in 2018. The normalized concentration indices increased from -0.149 (95% CI: -0.161 to -0.137) in 2011 to -0.176 (95% CI: -0.163 to -0.188) in 2018. The primary contributors to inequality were socioeconomic status, age, social activity participation and city development, while medical insurance and city hospital beds per capital had mitigating effects. Conclusions Efforts to address this inequality should encompass policy considerations to diminish SES disparity, foster equitable resources across cities, and sustain healthcare insurance initiatives.