Cognitive impairment is independently associated with mortality, extended hospital stays and early readmission of older people with emergency hospital admissions: A retrospective cohort study

Background: Older adults admitted to hospital are often cognitively impaired. It is not clear whether the presence of cognitive impairment conveys an additional risk for poor hospital outcomes in this patient population.

Objectives: To determine whether cognitive impairment in hospitalised older adults is independently associated with poor outcomes.

Design: Retrospective cohort study using electronic, routinely collected data from linked clinical and administrative databases.

Setting: Large, acute district general hospital in England.

Participants: 21,399 incident emergency admissions of people aged ≥75, screened for cognitive impairment, categorised to 3 groups: (i) cognitive impairment with a diagnosis of dementia, (ii) cognitive impairment with no dementia diagnosis, (iii) no cognitive impairment.

Methods: Multivariable logistic regression and Fine and Gray competing risks survival models were employed to explore associations between cognitive impairment and mortality (in-hospital alone, and in-hospital plus up to 30 days after discharge), time to hospital discharge, and hospital readmission within 30 days of discharge. Covariates included age, severity of illness, main diagnosis, comorbidities and nutritional risk.

Results: Twenty-seven percent of patients had cognitive impairment; of these, 61.5% had a diagnosis of dementia and 38.5% did not. Patients with cognitive impairment and no diagnosis of dementia were most likely to die in hospital or be readmitted, they also had the longest hospital stays. Cognitive impairment was independently associated with mortality in hospital (Odds Ratio 1.34 [1.17-1.55] with dementia; Odds Ratio 1.78 [1.52-2.07] without), mortality in hospital or within 30 days of discharge (Odds Ratio 1.66 [1.48-1.86]; Odds Ratio 1.67 [1.46-1.90]); readmission (Odds Ratio 1.21 [1.04-1.40]; Odds Ratio 1.47 [1.25-1.73]), and increased time until discharge (sub-hazard ratio 0.80 [0.76-0.83]; sub-hazard ratio 0.66 [0.63-0.69]).

Conclusions: Cognitive impairment is associated with an increased risk of adverse outcomes in hospitalised older people with an unscheduled admission, by increasing hospital mortality, extending hospital stays and increasing frequency of readmissions. Future research should focus on understanding the mechanisms contributing to poorer outcomes in this population.