Delirium in the non-demented oldest old in the general population: risk factors and prognosis.

Abstract

The oldest old are prone to develop delirium. Studies into risk factors for delirium have been carried out predominantly in younger age groups. The aim of this population-based follow-up study was to investigate the risk factors for delirium requiring medical attention and subsequent prognosis in the non-demented general population aged > or = 85 years. The study included the non-demented subjects in the population-based Vantaa 85+ study. After the 3-year observation period, 199 subjects (91% of those surviving) were re-examined and their medical records were evaluated for episodes of delirium. The subjects were followed up with respect to mortality for another 2 years. During the 3-year observational period, 20 subjects (10%) had been diagnosed as having had an episode of delirium. A Mini-Mental State Examination score of < 24 (odds ratio (OR) 3.44, confidence interval (CI = 95%) 1.27-9.32) and high systolic blood pressure (OR 3.08, CI 1.08-8.79) were identified as independent risk factors for delirium. The association between the delirium episode and a new diagnosis of dementia was significant ( p = 0.001). The mortality rate was greater among those subjects who experienced delirium than among subjects without this syndrome ( p = 0.008). Mild cognitive impairment and high systolic blood pressure were found to be risk factors for delirium requiring medical attention in the general non-demented population aged > or = 85 years. The study also highlights the significant association between delirium and a new dementia diagnosis in this age group.