Maladie et dépendance : description des évolutions par des modèles multi-états

Gauzère Franck, Commenges Daniel, Barberger-Gateau Pascale, Letenneur Luc, Dartigues Jean-François.- Illness and dependency: description of changes using multistate models The progression of an illness can be modelled with a three-state model: healthy, ill, dead. The model used in this article contains no reversible transitions: it is fully specified by the transition intensities between the different states. Such an approach is of value in epidemiology, because the transition intensities to the dead state represent the instantaneous death rates for the ill and healthy, while the transition intensity from the healthy state to the sick state corresponds to the instantaneous incidence of the illness. Smoothed estimates are given for the different transition intensities between the different states; the probability of occupying a given state at a given age can be inferred from the intensities, and the prevalence of the illness is calculated by the ratio between the probability of being ill and the probability of being alive. This method is applied here to data from the PAQUID study to describe the evolution of serious dependency among elderly people over 65 living in southwest France. The prevalence of serious dependency increases with age for both sexes. The age-related increase in the intensities of the transition to dependency is faster for women than for men.