|CHAPTER 1: FUNCTIONING, DISABILITY AND HEALTH
|Year : 2019 | Volume
| Issue : 2 | Page : 13-14
1.2 Epidemiology of Disability
Gerold Stucki, Jerome Bickenbach
Department of Health Sciences and Health Policy, University of Lucerne, Lucerne; Swiss Paraplegic Research; ICF Research Branch, a Cooperation Partner within the WHO Collaborating Centre for the Family of International Classifications in Germany (at DIMDI), Nottwil, Switzerland
|Date of Web Publication||11-Jun-2019|
Prof. Gerold Stucki
Department of Health Sciences and Health Policy, University of Lucerne, Lucerne; Swiss Paraplegic Research; ICF Research Branch, a Cooperation Partner within the WHO Collaborating Centre for the Family of International Classifications in Germany (at DIMDI), Nottwil
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Stucki G, Bickenbach J. 1.2 Epidemiology of Disability. J Int Soc Phys Rehabil Med 2019;2, Suppl S1:13-4
The International Classification of Functioning, Disability and Health (ICF) provides the foundations for a true epidemiology of disability. At the population level, disability has traditionally be estimated at the national level in one of two ways: (i) by means of surveys or questionnaires involving proxy variables, often the prevalence of specific diseases or other health conditions, (ii) by results from self-response questions in population health surveys concerning capacity difficulties in basic activities – seeing, hearing, walking, climbing steps, remembering, washing, communicating – or in activities of daily living or instrumental activities of daily living. Proxy measures of prevalence, the evidence suggests, are of questionable reliability, although especially in low- and medium-resource countries these shortcuts are unavoidable because running surveys is expensive. Beyond providing rough estimates of disability prevalence, these proxy approaches provide very little additional information and certainly do not provide the data for a statistically robust epidemiology of disability.
Due to the important demographic and epidemiological trends mentioned above, rehabilitation practice and health-care practice and planning generally will increasingly require more than these modest attempts at rough estimates of the global or national prevalence. Here, the ICF provides researchers and policy-makers with a roadmap of what is required. First of all, the ICF makes it clear that what needs to be measured are decrements of functioning across a set of domains that, evidence has suggested, provide data with strong predictive power. This entails two kinds of decisions that need to be mapped, both of which are anticipated by the ICF model.
It first must be determined whether our epidemiological concerns are focused on specific health conditions or impairments, or whether we only require information about the overall quantity of disability experienced by the population. If, for example, we require information about the impact of the increasing of dementia in the coming decades, our survey must focus on domains of functioning that research has shown are especially vulnerable to this health condition. Other policy or planning purposes may not require this level of disease-specific specification, but instead a more global estimate of the impact of the predicted prevalence of conditions known to have a high-disease burden.
Second, depending on our scientific, clinical, or policy requirements, we may either need to determine through a survey the extent of the aggregate, intrinsic health states or capacity of the population – in light, for example, of aging trends – or to determine how the population actually performs in a collection of domains representing important life activities such as parenting, educational or labor participation, or community participation. When the focus is on performance in the ICF sense, surveys cannot be restricted to features of the individual, but must be extended to include factors in the person's environment, both those that hinder full participation and those that facilitate it. Both the capacity and the performance dimensions provide information required to begin to understand the dynamics and determinants of disability at the population level and the nature and challenges of rehabilitation as a health strategy. In addition, both are essential components of a true epidemiology of disability.
In its comprehensive 2011 World Report on Disability, the World Health Organization (WHO) relies on a complex modeling exercise, incorporating a variety of national and international data sets, to provide a baseline estimate of global prevalence of disability, standardized for age and sex, in terms of severe difficulties in functioning. Worldwide prevalence rates were found to be roughly 15%, although the report was quick to say that this was not definitive and that more reliable and comprehensive national and international data on disability were urgently needed. In response, and in line with its Disability Action Plan, WHO is now taking steps to provide the groundwork for a true disability epidemiology by developing and field testing the Model Disability Survey (MDS). The MDS clearly distinguishes the capacity from the performance perspectives, in order to disentangle intrinsic health determinants of disability from the environmental determinants. The MDS not only makes it possible to identify rehabilitation outcomes along the disability continuum for those who experience severe, moderate, and mild disability, but it also enables decision-makers to go beyond to identifying the factors that are responsible for inequalities, in particular, and allows them to identify appropriate and effective interventions and policies. The MDS is an example of the kind of developments in survey methodology that will make it possible to fulfill the promise of a true epidemiology of disability.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| References|| |
World Health Organization. The International Classification of Functioning, Disability and Health (ICF). Geneva: World Health Organization; 2001.
World Health Organization, World Bank. Disability – A global picture. World Report on Disability. Ch. 2. Geneva: World Health Organization; 2011.
Salomon J, Mathers C, Chatterji S, Sadana R, Üstün TB, Murray CJ. Quantifying individual levels of health: Definitions, concepts, and measurement issues. In: Murray CJ, Evans DB, editors. Health Systems Performance Assessment: Debates, Methods and Empiricism. Geneva: World Health Organization; 2003. p. 301-18.