Longer inpatient delirium time associated with worse cognition a year later

Inpatients who spent more time in delirium had worse cognition and executive function scores at 3 and 12 months, a new study found.

In a multicenter, prospective cohort study, researchers examined 821 patients with respiratory failure, cardiogenic shock or septic shock in surgical and medical ICUs. Inpatients were evaluated for delirium (using the Confusion Assessment Method for the ICU) and level of consciousness (using the Richmond Agitation-Sedation Scale) every day until day 30 or hospital discharge.

Separate researchers, who were unaware of the patients' hospital courses, then assessed the patients' global cognition at 3 and 12 months after discharge using the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) and the Trail Making Test, Part B. The researchers used linear regression to examine any associations between duration of delirium, use of analgesic and sedative agents, and outcomes. Results were published online Oct. 3 by the New England Journal of Medicine.

Six percent of patients had cognitive impairment at baseline, and 74% developed delirium while in the hospital. At 3 months, 40% of patients scored 1.5 SDs below the mean in global cognition, similar to scores of patients who have moderate traumatic brain injury. Twenty-six percent of patients had scores 2 SDs below the mean, similar to scores of patients with mild Alzheimer disease.

At 12 months, 34% and 24% of patients had scores at 1.5 and 2 SDs below the mean, respectively. A longer duration of delirium was independently associated with lower global cognition at 3 and 12 months (P=0.001 and P=0.04, respectively), as well as lower executive functioning (P=0.004 and P=0.007 at 3 and 12 months, respectively). Cognitive impairment wasn't associated with analgesic or sedative drug use, and deficits occurred in both older and younger patients.

Though the results were similar to previous studies showing cognitive deficits in ICU survivors, this study is different in that it enrolled a large sample of patients with a broad age range and diverse diagnoses, and detailed data were collected about delirium and sedative exposure as risk factors, the authors noted. A limitation, however, was that researchers couldn't test patients' cognition before their emergent illness, though the researchers did attempt to account for this via exclusions, stratification and statistical adjustments, they added.

Editorialists wrote that the study “unequivocally establishes that critical illness promotes the development of new and clinically important cognitive impairment, regardless of age, burden of coexisting conditions and diagnosis at hospital admission.” The results highlight the important of monitoring for delirium in the ICU and intervening, as well as practicing wake-up and mobility protocols, they wrote.