‘Disability’ is an umbrella term for any or all of impairments, activity limitations and participation restrictions, as influenced by environmental factors; disability is defined in the context of health, and health conditions and personal factors are also part of the interactive model (WHO 2001; see more discussion in Section 1.2).

Despite the acknowledged links between health and disability, there has not been a great deal of analysis on how they relate to each other. Disability or aged care policies and programs frequently focus on activity limitations (for instance, limitations in mobility) and participation restrictions (for instance, restrictions in employment); these programs often provide personal assistance, aids or environmental modifications but do not usually delve into the related health condition.

Related population analyses focus on ‘disability’ as a summary measure in its own right—for instance, in terms of the numbers of people in the population needing assistance with mobility activities. Health-focused analyses that also look at disability may, in contrast, seek to explain health outcomes (or ‘burdens’ or costs) in terms of ‘disabilities’ attributed, by some means, to specific health conditions. Where multiple health conditions and/or multiple disabilities exist, these analyses pose difficult problems. ‘Disability’ in the population then becomes a complex and constructed summary measure, apportioned among and combined across a range of health conditions.