Socio-economic inequalities in health-related quality of life and the contribution of cognitive impairment in Australia: A decomposition analysis

Background: The distributional effects of cognitive impairment on inequalities in health-related quality of life (HRQoL) are not well studied. This relationship has not been studied in any Australian health inequality literature. Therefore, this study aims to examine how cognitive impairment affects the distribution of HRQoL across various socio-economic classes amongst older Australians. Methods: Data for this study was collected from the Household, Income and Labour Dynamics in Australia (HILDA) survey. The final analysis consisted of 5,247 and 5,614 unique individuals from wave 2012 and wave 2016, respectively. An ordinary least squares (OLS) regression model was used to investigate the relationship between cognitive impairment and HRQoL. Additionally, the Wagstaff-Doorslaer-Watanabe standard concentration index was used to examine socioeconomic inequality in HRQoL. Results: The findings revealed pro-rich inequalities in HRQoL, as indicated by the concentration indices of 0.029 and 0.025 for wave 12 and wave 16, respectively. Additionally, the results showed that mild cognitive impairment accounted for 7.60% and 9.03%, respectively, of pro-rich socioeconomic inequality in HRQoL in 2012 and 2016. Conclusion: People from lower socioeconomic status (SES) groups tend to have lower HRQoL compared to those from higher SES. This leads to a greater disparity in HRQoL based on SES. Cognitive impairment positively contributed to this inequality in HRQoL. Therefore, it is critical to incorporate cognitive impairment into the design of interventions to reduce socioeconomic inequality in HRQoL.