Under-detection of delirium and impact of neurocognitive deficits on in-hospital mortality among acute geriatric and medical wards

Background: Delirium is a neuropsychiatric disorder, triggered by medical precipitants causes. Study aims were to describe the prevalence and impact on in-hospital mortality of delirium identified through ICD-9 codes as well as evidence of neurocognitive deficits demonstrated in a population of older patients admitted to acute medical wards.

Methods: This was a prospective cohort multicenter study of 2521 older patients enrolled in the "Registro Politerapie SIMI (REPOSI)" during the years 2010 and 2012. The diagnosis of delirium was obtained by ICD-9 codes. Cognitive function was evaluated with the Short Blessed Test (SBT) and single SBT items were used as measures of deficits in attention, orientation and memory. Combination of deficits in SBT items was used as a proxy for delirium. Logistic regression was used to evaluate the association with in-hospital mortality of delirium and combined deficits in SBT items.

Results: Delirium was coded in 2.9%, while deficits in attention, orientation, and memory were found in 35.4%, 29.7% and 77.5% of patients. Inattention and either disorientation or memory deficits were found in 14.1%, while combination of the 3 deficits in 19.8%. Delirium, as per ICD-9 codes, was not a predictor of in-hospital mortality. In contrast, objective deficits of inattention, in combination with orientation and memory disorders, were stronger predictors after adjusting for covariates.

Conclusions: The documentation of delirium is poor in medical wards of Italian acute hospitals. Neurocognitive deficits on objective testing (in a pattern suggestive of undiagnosed delirium) should be used to raise awareness of delirium, given their association with in-hospital mortality.