Association between Delirium and Cognitive Impairment: Is there a Link?

Background: Delirium and dementia are both disorders involving global cognitive impairment that can occur separately or at the same time in the elderly.

Objective: The aim of this study was to examine the frequency, correlation, and relative risk between delirium and cognitive impairment in a prospective population study starting at the basal line (onset of delirium) over a period of five years. The secondary aim was to determine any possible correlation between the kind of delirium and a specific type of dementia.

Materials and methods: We studied 325 patients diagnosed according to the DSM-IV. The neuropsychological, moods and delirium disorders were evaluated with Hamilton Depression Rating Scale, Delirium Rating Scale-Revised-98, MMSE, Rey auditory-verbal learning test, Digit Span, Symbol Digit Modalities Test, Raven Progressive Matrices, ADL, and IADL.

Results: The prevalence of delirium in our population was 89 cases (27.4%): 78 patients (48 women and 30 men) showed evolution toward dementia (mean age was 67.9 ± 6.1 years for men and 68.4 ± 9.1 for women), and 11 patients (5 men and 6 women) presented only isolated delirium without evolution toward cognitive impairment (mean age of men was 68.1 ± 5.1 years and of women 66.4 ± 7.1). The neuropsychological study of the patients with delirium with dementia evolution revealed statistically significant differences over time with a statistically significant intergroup difference and predisposition toward depression.

Conclusion: The association between delirium and cognitive impairment and the possible role of delirium as an early marker of neurodegenerative diseases need to be investigated in the future.