For a long time, knowledge of life expectancy at different ages, the infant mortality rate and the distribution of the causes of death according to the principal disease headings was sufficient to assess the health status of populations and to determine national public health priorities. However, during the last 20 years the need for a new type of indicator has arisen as a result of changes such as the lengthening of life expectancy due to the fall in mortality at older ages, and the issue of quality of the years lived, at very old ages in particular.
As not much is known about the limits of human longevity, health expectancy indicators - which provide information on the population's functional state and on its vitality as well as on its quality of life - are well adapted to the new conditions.
Life expectancy without severe disability at age 65 in men has been shown to progress roughly in parallel with total life expectancy. Whatever the country examined, the increase in life expectancy is not accompanied by an increase in the time spent with severe disability the results indicate at worst a pandemic of light and moderate, but not of severe disabilities.