Prospective cohort study of adverse events in older people admitted to the acute general hospital: risk factors and the impact of dementia

Background: Reported adverse events (RAEs) are relatively common in the acute hospital and are associated with significant mortality and morbidity. Dementia is increasing in hospital in-patients, however there have been few studies exploring risk factors for RAEs, in particular cognitive impairment and dementia. Our objective was to identify the prevalence of RAEs in older acute medical inpatients and associated demographic, clinical or cognitive risk factors.

Method: A longitudinal cohort study set on acute medical wards in a large general hospital. We recruited 710 people aged over 70 years undergoing emergency medical admission. Dementia was diagnosed using operationalised DSM-IV criteria. Patients were assessed using standardised tools including the Confusion Assessment Method, mini-mental state examination, the Functional Assessment Staging scale, the APACHE scale and Charlson co-morbidity index. Data on adverse events was supplied independently by the hospital clinical risk department.

Results: 8.6% (95% CI 6.4-10.6) of patients experienced an RAE; 5.9% (95% CI 4.2-7.6) were patient-related and 2.7% (95% CI 1.5-3.8) system-related (incidence rate for all RAEs was 2.1 (95% CI 1.7-2.8)) per person year of hospital admission. Median length of admission was 8 days (inter-quartile range 4-17 days). Patient-related RAEs were associated with male gender, delirium, mild/moderate cognitive impairment and a FAST score of 2-6. Overall, 11.1% died during the admission-this was not associated with experiencing an RAE. Staff comments on incident forms indicated an apparent lack of understanding of the impact of cognitive impairment.

Conclusions: RAEs were common and associated with risk factors identifiable at admission.