[Polypathology and co-morbidity: a dynamic way for describing morbidity in aged patients. Study of 100 patients, aged 80 and over, in a short-stay geriatric internal medicine unit].

Descriptive epidemiology has demonstrated the increase with age of the number of identifiable diseases per subject. However, the clinical relevance of this polypathology varies according to the type of affliction, and all pathologies are not necessarily implicated in all morbid events. This prospective study analyzed the length of hospitalization (mean stay: 17.26 +/- 10.52 days) of 100 subjects at least 80 years old (mean age: 85.2 +/- 4.35 yr). The mean total number of recognized diseases per patients was 4.12 +/- 1.83 (range: 1-10). The mean number of diseases concerned by the hospitalization studied was 3.13 +/- 1.60 (range: 1-9). Dynamic analysis of the morbidity of these patients led to their classification into two groups: a) co-morbid patients with several diseases among which interaction is not possible; and b) polymorbid patients with several diseases able to interact. In a polymorbid patient, a disease event can occur as the result of such an interaction (leading to multiple organ failure) or the evolution of a single entity. The number of diseases concerned by the hospitalization varied significantly according to the different models of morbidity, which reflect the different types of medical activity. The lengths of the hospital stay observed did not seem to be influenced by the morbidity model, thereby indicating the existence of other factors prolonging hospitalization. The data collected supported the validity of this approach to disease in the elderly whose objective is a new description of medical activity in this population.