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

BACKGROUND: 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.

METHOD: 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.

RESULTS: 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).

CONCLUSIONS: 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.