JEAN-MARIE ROBINE, COLIN MATHERS, AND NICOLAS BROUARD
In the introduction to the International Classification of Impairments, Disabilities, and Handicaps (ICIDH), the World Health Organization (WHO) has argued that the classical medical model (of aetiology--pathology--manifestation) is incomplete 'because it stops short of the consequences of disease. It is the latter, particularly, that intrude upon everyday life . . . this is especially true for chronic and progressive or irreversible disorders'. More generally, WHO has thus proposed the following model:
WHO defines these terms as follows: 'impairments' are concerned with abnormalities of body structure and appearance and with organ or system function, resulting from any cause; in principle, impairments represent disturbances at the organ level; 'disabilities': reflect the consequences of impairment in terms of functional performance and activity by the individual; disabilities thus represent disturbances at the level as a person; 'handicaps' are concerned with the disadvantages experienced by the individual as a result of impairments and disabilities; handicaps thus reflect interaction with and adaptation to the individual's surroundings ( WHO, 1980). According to WHO, impairments and disabilities can express themselves in nine different fields and handicaps in seven (see Table 9.1).
With these concepts, one can differentiate among various forms of health expectancies (see Figure 9.1): impairment-free life expectancy, disability- free life expectancy, and handicap-free life expectancy. It is also possible to distinguish between levels of severity (for example, severe disability- free life expectancy) and thus test the various hypotheses relating to the theories of 'compression of morbidity', 'pandemic', or 'equilibrium' by contrasting or distinguishing between 'tested abilities' and 'performances in daily life'.