Delirium accelerates cognitive decline in Alzheimer disease

Abstract

Objective: To examine the impact of delirium on the trajectory of cognitive function in a cohort of patients with Alzheimer disease (AD).

Methods: A secondary analysis of data collected from a large prospective cohort, the Massachusetts Alzheimer's Disease Research Center's patient registry, examined cognitive performance over time in patients who developed (n = 72) or did not develop (n = 336) delirium during the course of their illnesses. Cognitive performance was measured by change in score on the Information-Memory-Concentration (IMC) subtest of the Blessed Dementia Rating Scale. Delirium was identified using a previously validated chart review method. Using linear mixed regression models, rates of cognitive change were calculated, controlling for age, sex, education, comorbid medical diagnoses, family history of dementia, dementia severity score, and duration of symptoms before diagnosis.

Results: A significant acceleration in the slope of cognitive decline occurs following an episode of delirium. Among patients who developed delirium, the average decline at baseline for performance on the IMC was 2.5 points per year, but after an episode of delirium there was further decline to an average of 4.9 points per year (p = 0.001). Across groups, the rate of change in IMC score occurred about three times faster in those who had delirium compared to those who did not.

Conclusions: Delirium can accelerate the trajectory of cognitive decline in patients with Alzheimer disease (AD). The information from this study provides the foundation for future randomized intervention studies to determine whether prevention of delirium might ameliorate or delay cognitive decline in patients with AD.

Figure Cognitive trajectories of patients with Alzheimer disease with and without delirium This figure depicts the slopes of the cognitive trajectories in patients with Alzheimer disease over time in our cohort. The median time to delirium from point B was 0.3 years (75% interquartile range, 0.13–0.45 years). The slopes are based on the changes in the Blessed Information-Memory-Concentration (IMC) subscore over time, and the scores presented are calculated adjusting for baseline differences. These slopes are derived from linear mixed models adjusted for relevant covariables (age, sex, educational level, Massachusetts General Hospital dementia severity rating score, duration of dementia symptoms before diagnosis, family history of dementia, and number of comorbid medical diagnoses). The solid line indicates the trajectory for patients with delirium (n = 72) and the dashed line indicates the trajectory for patients without delirium (n = 336).