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

Background: Physical functional disability is prevalent among middle-aged and older adults, with substantial health inequality. This study compared cross-country 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 functions were grouped into three domains: activities of daily living (ADLs), instrumental activities of daily living (IADLs), and mobility function. Physical functional 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) decomposition method was used to decompose the inequality into individual and country-level determinants. Results: Physical functional disability prevalence was higher in lower-middle-income countries than in high-income countries and more prevalent in the poor-income groups in all study countries. Besides, health inequality in different domains 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 resources 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 determinants being contributing factors. Policies to achieve healthy ageing and reduce the inequality of physical function disability can focus on improving individual healthy lifestyles and country health care facilities.