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

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 offollow-up. This study examines mortality in older people with any cognitive impairment duringacute hospital admission.Patients and methods: Prospective cohort of 6,724 people aged ≥65 years with a structuredcognitive assessment on acute admission were included in this study. Cognitive spectrum disorder(CSD) was defined as delirium alone, known dementia alone, delirium superimposed on knowndementia, or unspecified cognitive impairment. Mortality associated with different types of CSDwas 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. Afteradjustment for demographics and comorbidity, delirium alone was associated with increasedmortality 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 superimposeddelirium) had increased mortality only after 3 months from admission (HR =1.85, 95% CI1.56–2.18 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 attenuatedassociations were seen after adjustment for functional ability.Conclusion: Mortality post-admission is high in older people with CSD. Immediate risk ishighest in those with delirium, while dementia or unspecified cognitive impairment is associatedwith medium- to long-term risk. These findings suggest that individuals without dementia whodevelop delirium are more seriously ill (have required a larger acute insult in order to precipitatedelirium) than those with pre-existing brain pathology (dementia). Further research to explainthe mortality patterns observed is required in order to translate the findings into clinical care