Epidemiology of disability and implications for practice.

The epidemiology of disability is a vast field aiming to bring more precise information about the 10% of the world's population that is disabled to the attention of national and local administrations. This information is essential for management of the problems of disability in an appropriate way and making best use of resources. The current epidemiological studies are done by different methods, and use non-standardized terminology with very free interpretation of the IDH concepts. The classifications--ICD and ICIDH--play their role in creating the disability databases. The challenge for the future is to harmonize all these processes.