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

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

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.

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.

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.

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.