Estimation of the degree of functional disability through a fuzzy model

Measures of functional levels are commonly used to assess the quality of life of individuals and populations. Although essentially subjective, such measures have not yet been derived from a fuzzy framework. A fuzzy linguistic model (MISO) was developed to measure varying levels of functional disability, based on definitions of an individual's social and physical activities and mobility, considered together. From the fuzzy model, one year of an adult's life who works but performs restrictively other social activities, needs help to use public transport and walks with physical limitations was judged to be equivalent to 0.575 years of well life, in the absence of any kind of functional disability. The amount of well years of life can be used as a common denominator to assess the impact of medical and public health interventions, both preventive and curative. When applied at a population level, it serves as a useful tool for priority setting and decision making purposes in public health.