Cross-country comparison of income-related inequality in physical functional disability among middle-aged and older adults: Evidence from 33 countries

Abstract

Background Physical functional disability is prevalent among middle-aged and older adults, with substantial health inequality. This study compared cross-coun-try variation in the prevalence and inequality of physical functional disability and investigated the potential determinants of household income-related inequality. Methods This cross-sectional study used data from 33 countries between 2017 and 2020, containing 141 016 participants aged 55 years and older. Physical func-tions were grouped into three domains: activities of daily living (ADLs), instru-mental activities of daily living (IADLs), and mobility function. Physical func-tional disability of each domain was indicated by having some difficulty with the activity. We first estimated the prevalence of physical functional disability in each country. Second, the concentration index was used to quantify household income-related health inequality. Finally, recentred influence function (RIF) de-composition method was used to decompose the inequality into individual and country-level determinants. Results Physical functional disability prevalence was higher in lower-middle -in-come countries than in high-income countries and more prevalent in the poor -in-come groups in all study countries. Besides, health inequality in different do-mains of disability was higher in high-income countries than in low-income countries. Regarding determinants of health inequality, we found that individual married, tertiary education, and country-level health infrastructure and resourc-es were associated with reduced health inequality. In contrast, age, unhealthy lifestyles, and chronic diseases were associated with increased health inequality. Conclusions Inequality in physical functional disability among middle-aged and older adults varies substantially across countries, with individual and macro de-terminants being contributing factors. Policies to achieve healthy ageing and re-duce the inequality of physical function disability can focus on improving indi-vidual healthy lifestyles and country health care facilities.