The short-term and long-term relationship between delirium and cognitive trajectory in older surgical patients

Abstract

Introduction: As the relationship between delirium and long-term cognitive decline has not been well-explored, we evaluated this association in a prospective study.

Methods: SAGES is an ongoing study involving 560 adults age 70 years or more without dementia scheduled for major surgery. Delirium was assessed daily in the postoperative period using the Confusion Assessment Method. General Cognitive Performance (GCP) and the Informant Questionnaire for Cognitive Decline in the Elderly were assessed preoperatively then repeatedly out to 36 months.

Results: On average, patients with postoperative delirium had significantly lower preoperative cognitive performance, greater immediate (1 month) impairment, equivalent recovery at 2 months, and significantly greater long-term cognitive decline relative to the nondelirium group. Proxy reports corroborated the clinical significance of the long-term cognitive decline in delirious patients.

Discussion: Cognitive decline after surgery is biphasic and accelerated among persons with delirium. The pace of long-term decline is similar to that seen with mild cognitive impairment.

Keywords: Acute confusional state; Cognitive decline; Delirium; Dementia; Geriatrics; Mild cognitive impairment; Surgical complications; Surgical outcomes.

Figure 1. GCP Trajectory by Delirium Status

Panel A demonstrates the relationship between the estimated General Cognitive Performance (GCP) scores derived from random effects models (y-axis) and time since surgery on a natural log scale (x-axis). In this figure, the models are adjusted for the effect of baseline GCP score in delirium and cognitive change, since preoperative cognition predicts delirium. Therefore, at baseline delirium status is unknown and both groups start at the overall sample mean value of GCP. The zero-time values represent the preoperative baseline, and follow-up time points are relative to the index surgery and placed on a log scale. The delirium group is indicated by the solid black line surrounded by its associated 95% confidence interval in dark gray shading. The no delirium group is indicated by a gray line, surrounded by its associated 95% confidence interval in light gray shading. Solid gray reference lines indicate the baseline level of GCP. The biphasic relationship of delirium with GCP over time is demonstrated. In the acute phase, patients with delirium experienced a significantly accentuated acute decline in cognitive impairment at 1 month and recovery back to baseline by 2 months. In the long-term phase, patients with delirium experienced a significantly higher rate of cognitive decline over time (see text for details). Panel B demonstrates the same models and relationships as Panel A, however, for these models, the starting point of the curves is offset by the mean difference in baseline GCP according to delirium status during hospitalization.

Figure 1. GCP Trajectory by Delirium Status

Panel A demonstrates the relationship between the estimated General Cognitive Performance (GCP) scores derived from random effects models (y-axis) and time since surgery on a natural log scale (x-axis). In this figure, the models are adjusted for the effect of baseline GCP score in delirium and cognitive change, since preoperative cognition predicts delirium. Therefore, at baseline delirium status is unknown and both groups start at the overall sample mean value of GCP. The zero-time values represent the preoperative baseline, and follow-up time points are relative to the index surgery and placed on a log scale. The delirium group is indicated by the solid black line surrounded by its associated 95% confidence interval in dark gray shading. The no delirium group is indicated by a gray line, surrounded by its associated 95% confidence interval in light gray shading. Solid gray reference lines indicate the baseline level of GCP. The biphasic relationship of delirium with GCP over time is demonstrated. In the acute phase, patients with delirium experienced a significantly accentuated acute decline in cognitive impairment at 1 month and recovery back to baseline by 2 months. In the long-term phase, patients with delirium experienced a significantly higher rate of cognitive decline over time (see text for details). Panel B demonstrates the same models and relationships as Panel A, however, for these models, the starting point of the curves is offset by the mean difference in baseline GCP according to delirium status during hospitalization.

Figure 2. IQCODE Trajectory by Delirium Status

The figure demonstrates the relationship between the estimated IQCODE score derived from a random effects model (y-axis) and time since surgery (x-axis). In this figure, the models are adjusted for baseline GCP score, since this score predicts delirium and therefore both groups start at the same mean value of GCP. Estimates are also adjusted for age, sex, race, English as a second language, Charlson comorbidity index and surgery type. The vertical dotted lines connecting the cotemporaneous estimates for delirious and non-delirious groups are labeled with the net effect differences (differences at that time point net of baseline differences). Proxy IQCODE ratings were available on 548 patients (98% of 560) at baseline and 290 patients (52% of 560) at 36 month follow-up.