Background: Delirium is a risk factor for dementia in cognitively intact patients. Whether an episode of delirium accelerates cognitive decline in patients with known dementia, is less explored.
Methods: This is a prospective follow-up study of 287 hip fracture patients with pre-fracture cognitive impairment. During the hospitalization, the patients were screened daily for delirium using the Confusion Assessment Method. Pre-fracture cognitive impairment was defined as a score of 3.44 or higher on the pre-fracture Informant Questionnaire on Cognitive Decline in the Elderly Short Form (IQCODE-SF). At follow-up after 4-6 months, the caregivers rated cognitive changes emerging after the fracture using the IQCODE-SF, and the patients were tested with the Mini Mental State Examination (MMSE). A sub-group of the patients had a pre-fracture MMSE score which was used to calculate the yearly decline on the MMSE in patients with and without delirium.
Results: 201 of the 287 patients developed delirium in the acute phase. In linear regression analysis, delirium was a significant and independent predictor of a more prominent cognitive decline at follow-up measured by the IQCODE-SF questionnaire (p=0.002). Among patients having a pre-fracture MMSE score, the patients developing delirium had a median (IQR) yearly decline of 2.4 points (1.1-3.9), compared to 1.0 points (0-1.9) in the group without delirium (p=0.001, Mann-Whitney test).
Conclusions: Hip fracture patients with pre-fracture dementia run a higher risk of developing delirium. Delirium superimposed on dementia is a significant predictor of an accelerated further cognitive decline.
Keywords: Cognitive trajectories; Delirium; Dementia; Hip fracture.
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