Socioeconomic Inequality in Disability Among Adults: A Multicountry Study Using the World Health Survey

Objectives. We compared national prevalence and wealth-related inequality in disability across a large number of countries from all income groups.Methods. Data on 218 737 respondents participating in the World Health Survey 2002–2004 were analyzed. A composite disability score (0–100) identified respondents who experienced significant disability in physical, mental, and social functioning irrespective of their underlying health condition. Disabled persons had disability composite scores above 40. Wealth was evaluated using an index of economic status in households based on ownership of selected assets. Socioeconomic inequalities were measured using the slope index of inequality and the relative index of inequality.Results. Median age-standardized disability prevalence was higher in the low- and lower middle-income countries. In all the study countries, disability was more prevalent in the poorest than in the richest wealth quintiles. Pro-rich inequality was statistically significant in 43 of 49 countries, with disability prevalence higher among populations with lower wealth. Median relative inequality was higher in the high- and upper middle-income countries.Conclusions. Integrating equity components into the monitoring of disability trends would help ensure that interventions reach and benefit populations with greatest need.The World Health Organization (WHO) estimates that there are more than 1 billion people in the world living with some form of disability, of whom nearly 200 million have considerable difficulties in functioning.1 Almost everyone will experience disability at some time in their lives. Those who live longer will endure increasing difficulties in everyday physical and mental functioning.1 The United Nations Convention on the Rights of Persons with Disabilities2 identified disability as an international priority area for concerted action.Reported disability prevalence rates are lower in low- and lower middle-income countries than in upper middle- and high-income countries.1 However, this may reflect different approaches to measuring and defining disability within and between individual countries and also different age distributions in the countries.3–5 Surveys conducted in developing countries tend to focus on impairments. In developed countries, the focus is often on broader areas of participation and the need for services.1 There is clearly a need to improve comparability between countries and studies, but in order to do this it is necessary to achieve consistency in definition and measurement.The term disability is often used to refer to difficulties undertaking everyday tasks. Specific functional characterizations related to the activities of daily living are beneficial for many purposes (e.g., assessing eligibility for specific benefits or interventions). However, as a construct, disability spans many health conditions encompassing capacity limitations in physical, mental, and social functioning.6 Disability is increasingly becoming a major public health issue, but before effective policy responses can be formulated, it is necessary to achieve clarification and agreement on definition and measurement.7Consistent with the WHO and World Bank World Report on Disability,1 we applied the International Classification of Functioning, Disability and Health (ICF)8 framework. Disability included limitations in functioning that result from interactions between the individual’s health condition (e.g., diseases, injuries, and disorders) and environmental factors. We focused on measuring decrements in functioning that could be experienced by individuals in their body functions or capacities to carry out a set of activities not necessarily linked to their underlying health condition.9Many authors have referred to specific domains of disability, aspects of functional status (e.g., mobility, blindness, or deafness), or specific population subgroups (e.g., institutionalized populations or older age groups) in the disability literature. In this study, disability refers to any decrement in functioning in a chosen set of domains, irrespective of health condition. Individuals with arthritis, heart disease, diabetes, or depression could experience decrements in functioning, as well as those who are deaf, blind, or paralyzed.Persons with disability experience worse socioeconomic outcomes than persons without disability. Disability correlates with disadvantage, but causation is multidirectional.1 Disability can lead to socioeconomic disadvantage and vice versa. There is country-level evidence of correlation between disability and various indicators of socioeconomic status (SES) such as education, income, and housing.10–12 Given the rapid aging of the world’s populations, extending knowledge of the social and economic determinants of disability is timely. Developing policies and interventions to target the determinants of these inequalities requires urgent policy attention at national and international levels. Building upon the World Report on Disability,1 we examined how disability prevalence is distributed within country-specific adult populations in accordance with a standardized wealth index of SES.Most previous studies were conducted in higher income countries.13–16 This work advances international understanding of socioeconomic inequality in disability because the analysis covered household survey data collected from a large number of countries at varying income levels.Although the World Report on Disability1 used the ICF definition, the Report did not detail how disability prevalence was distributed within country-specific adult populations in accordance with SES. We aimed to measure and compare national prevalence and wealth-related inequality in disability among adults, aged 18 years and older, across a large number of countries from all income groups using a comparable data set and measurement method.