Delirium during psychiatric admission increases mortality in psychiatric patients during and after hospitalization. A nationwide study from 1995 through 2012

Objective: Delirium is a common acute neuropsychiatric disorder caused by a variety of physical insults. It is commonly associated with a variety of serious adverse outcomes, including elevated mortality. There are few studies of delirium occurring in psychiatric patients, including its mortality. The aim was to determine the psychiatric diagnostic profile of Danish psychiatric inpatients diagnosed with delirium and to compare standardized mortality ratio (SMR) in this group with the Danish population and general psychiatric inpatients from 1995 through 2012. Methods: All first time ICD-10 diagnoses of delirium among psychiatric inpatients were identified in the nationwide Danish Psychiatric Central Research Register (DPCRR) from 1995 through 2012. Results: A total of 7179 persons diagnosed with delirium were identified in the DPCRR between 1995 and 2012. Of these patients 40.8% had more than one diagnosis of delirium during the period. We identified three distinct groups, based on the first delirium-diagnosis; unspecified delirium (76.9%), comorbid delirium-dementia (19.8%), and drug-related delirium (3.3%). Use of sedative-hypnotics was noted in 46% of those with drug-related delirium. The SMR of delirious psychiatric inpatients compared to all psychiatric inpatients was stable at 1.7 throughout the time period. Conclusion: Delirium occurring in psychiatric inpatients is associated with elevated mortality. Sedative-hypnotic agents are commonly involved in drug-related delirium. Particular preventative effort is warranted for patients with a previous history of delirium, as we found approximately 40% with more than one episode of delirium.