Long-term Cognitive Impairment After Critical Illness

People who survive life-threatening illness often have long-term, disabling cognitive impairment. However, few studies have addressed this serious complication.

The investigators studied 821 adults with respiratory failure or shock in the medical or surgical intensive care unit. At baseline, 6% had cognitive impairment, and 74% developed delirium during their hospitalization. Using the Repeatable Battery for the Assessment of Neuropsychological Status and the Trail Making Test, Part B, the investigators tested global cognition and executive function at 3 and 12 months after discharge.,

Global cognition scores at 3 months were 1.5 SD below the population means (or similar to scores for patients with moderate traumatic brain injury) in 40% of patients. Scores were 2 SD below the population means (or similar to scores for patients with mild Alzheimer disease) in 26% of patients. Younger patients as well as older patients had these deficits, which were persistent. At 12 months, 34% of all patients had scores similar to those with moderate traumatic brain injury, and 24% had scores similar to those with mild Alzheimer disease.

Longer duration of delirium was an independent predictor of worse global cognition at 3 months (P = .001) and at 12 months (P = .04) and of worse executive function at 3 months (P = .004) and at 12 months (P = .007). In contrast, sedative or analgesic use was not consistently associated with cognitive impairment at 3 and 12 months, after adjustment for delirium.

This large, multicenter, prospective cohort study with a diverse patient population had several limitations. These included inability to test patients’ cognition before their illness, inability of some patients to complete all cognitive tests, and possible bias related to unmeasured confounders.

Nonetheless, this study showed that cognitive impairment after critical illness is very common and may persist in some patients for at least 1 year. At 12 months after critical illness, 1 of every 4 patients had cognitive impairment similar in severity to that of patients with mild Alzheimer disease, and 1 of 3 had impairment similar to that seen in moderate traumatic brain injury.

Cognitive deficits were more likely in patients with a longer duration of delirium. Although the mechanisms underlying this association are still unclear, delirium is associated with inflammation and neuronal apoptosis, which may result in brain atrophy. These findings suggest that interventions to reduce delirium could have the potential to reduce brain injury associated with critical illness.

Source: NEJM