Measuring Disability in Population-Based Surveys: The relationship between clinical impairments, self-reported functional limitations and equal opportunities in two Low and Middle Income Country settings

Background: Measuring disability in population-based surveys is imperative to support the meaningful inclusion of persons with disabilities in their societies. Disability is a complex bio-psycho-social phenomenon incorporating dysfunctioning in any of three interlinked levels (impairments in body function or structure, activity limitations or participation restrictions), resulting from the interaction between a health condition and contextual factors. There is little consensus on how to measure different components of disability in population-based surveys, or how these components inter-relate. A comprehensive population-based methodology is needed to be able to assess the prevalence and lived experience of disability, incorporating the three levels at which dysfunctioning occurs. Study Aim: To develop and undertake a comprehensive population-based survey methodology of disability in two settings and i) use this to explore the inter-relationship between tools measuring different components of disability ii) assess the prevalence and iii) lived experience of disability, including predictors of inclusion. Methods: A scoping review of the literature was undertaken to inform the development of an all-age population-based survey of disability. Population-based surveys (n=4080) of disability incorporating measures of impairment (vision, hearing, musculoskeletal, depression), activity limitation (Washington Group Extended Set) and participation restrictions (SINTEF participation module) were undertaken in one district each of Cameroon (North West Region, 2013) and India (Telangana State, 2014). A nested case-control study of people with and without disabilities was undertaken, to identify predictors of inclusion (e.g. access to health and rehabilitation, education, livelihoods). Key Findings: Overall disability prevalence was 12.2% (India) and 10.5% (Cameroon). Approximately 40% of people in each setting who screened positive for a clinical impairment did not report a functional limitation. A self-reported functional limitation tool followed by clinical screening of all those who report any level of difficulty would identify 94% of persons with disabilities in Cameroon and 95% in India, meeting the study criteria. Persons with disabilities in both settings experienced unequal opportunities. Children with disabilities were at least ten times less likely to be enrolled in education than children without disabilities; whilst adults with disabilities were five times less likely to be working than adults without disabilities, and between twice (Cameroon) and three times (India) more likely to have experienced a significant health problem in the past year. Conclusion: This study provides a suggested way forward for the measurement of disability in population-based surveys that would support the meaningful inclusion of persons with disabilities in their societies.