Mortality in people with dementia, delirium and unspecified cognitive impairment in the general hospital: prospective cohort study of 6724 patients with two years follow-up

Simona Hapca (Lead / Corresponding author), Bruce Guthrie, Feifei Bu, Alasdair Rutherford, Emma Reynish, Peter Donnan

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Abstract

Purpose: Cognitive impairment is common in older people admitted to hospital, but the outcomes are generally poorly understood, and previous research has shown inconsistent associations with mortality depending on the type of cognitive impairment examined and duration of
follow-up. This study examines mortality in older people with any cognitive impairment during
acute hospital admission.

Patients and methods: Prospective cohort of 6,724 people aged ≥65 years with a structured
cognitive assessment on acute admission were included in this study. Cognitive spectrum disorder
(CSD) was defined as delirium alone, known dementia alone, delirium superimposed on known
dementia, or unspecified cognitive impairment. Mortality associated with different types of CSD
was examined using a non-proportional hazards model with 2-year follow-up.

Results: On admission, 35.4% of patients had CSD, of which 52.6% died within 2 years. After
adjustment for demographics and comorbidity, delirium alone was associated with increased
mortality in the 6 months post-admission (HR =1.45, 95% CI 1.28–1.65) and again after 1 year
(HR =1.44, 95% CI 1.17–1.77). Patients with known dementia (alone or with superimposed
delirium) had increased mortality only after 3 months from admission (HR =1.85, 95% CI
1.56–2.18 and HR =1.80, 95% CI 1.52–2.14) compared with patients with unspecified cognitive impairment after 6 months (HR =1.55, 95% CI 1.21–1.99). Similar but partially attenuated
associations were seen after adjustment for functional ability.

Conclusion: Mortality post-admission is high in older people with CSD. Immediate risk is
highest in those with delirium, while dementia or unspecified cognitive impairment is associated
with medium- to long-term risk. These findings suggest that individuals without dementia who
develop delirium are more seriously ill (have required a larger acute insult in order to precipitate
delirium) than those with pre-existing brain pathology (dementia). Further research to explain
the mortality patterns observed is required in order to translate the findings into clinical care.
Original languageEnglish
Pages (from-to)1743-1753
Number of pages11
JournalClinical Epidemiology
Volume10
DOIs
Publication statusPublished - 23 Nov 2018

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