Delirium is a Acute Confusional State caused by physiological consequences of a medical disease, and is a predictive index of severity disease and survival time.

In this Study we valued, on random pool of 123 patients, the populations of older over 90yr aged recovered (29 patients) in the care of a RSA (Residential Sanitary Assisted in Italy or Nursing Home), compared with population younger afferent in RSA.

In the populations recovered in RSA studied is evident the prevalence of Delirium in the population over 90 year aged is most common compared to other population studied (44% vs 17%), as major seem to be the Incidence of Delirium in over 90 year population (33,3% vs 12,76%).

This data confirm the existence of biological frailty in the very old over 90 year aged.

Moreover this data demonstrate reduction of rates Delirium's Incidence compared with prevalence's rates in a Setting of Care focused elderly needs as RSA as other Non Geriatric Acute Setting. The 3-Months Mortality is major in the 90 year old compared to non 90 year old population (33,3% vs 18%) confirming a predictive role of Delirium.

This study showed Delirium is a Marker of Biological Frailty and it is an index predictive inauspicious about the survival of patient. Moreover is marked the RSA - Territorial Structures High Psycho-Geriatrics Contents - performs important role of delirium's prevention by means of removal of the risk factor avoidable and a careful control of causes.