In 1984, World Health Organisation (WHO) has proposed a demo-epidemiological model which allows the assessment of the possible consequences of the lengthening of life on the level of health. This model is represented in a graphic form by three curves: the observed survival curve, the hypothetical survival curve without chronic diseases and the hypothetical survival curve without disability; thus, as life expectancy at any age is calculated from the survival curve, this model allows the computation of life expectancy without chronic diseases and life expectancy without disability. The relationships between the three curves, can be used to illustrate the numerous theories dealing with the evolution of the populations' health which enliven debates in public health since several decades. Application of the model to French data on mortality, morbidity and disability also allows to enlighten the evolution of the health status of the French population over the last decade.