Impaired olfaction and risk of delirium or cognitive decline after cardiac surgery

Abstract

Objectives: To determine the prevalence of impaired olfaction in individuals presenting for cardiac surgery and the independent association between impaired olfaction and postoperative delirium and cognitive decline.

Design: Nested prospective cohort study.

Setting: Academic hospital.

Participants: Individuals undergoing coronary artery bypass, valve surgery, or both (n = 165).

Measurements: Olfaction was measured using the Brief Smell Identification Test, with impaired olfaction defined as an olfactory score below the fifth percentile of normative data. Delirium was assessed using a validated chart review method. Cognitive performance was assessed using a neuropsychological testing battery at baseline and 4 to 6 weeks after surgery.

Results: Impaired olfaction was identified in 54 of 165 participants (33%) before surgery. Impaired olfaction was associated with greater adjusted risk of postoperative delirium (relative risk = 1.90, 95% confidence interval = 1.17-3.09, P = .009). There was no association between impaired olfaction and change in composite cognitive score in the overall study population.

Conclusion: Impaired olfaction is prevalent in individuals undergoing cardiac surgery and is associated with greater adjusted risk of postoperative delirium but not cognitive decline. Impaired olfaction may identify unrecognized vulnerability to postoperative delirium in individuals undergoing cardiac surgery.

Keywords: cognition disorders; delirium; olfaction disorders.

© 2015, Copyright the Authors Journal compilation © 2015, The American Geriatrics Society.

Figures

Figure 1. Change in cognitive Z-scores between patients with impaired and normal baseline olfaction scores, according to baseline cognitive status

Distribution of predicted change in composite cognitive Z-score from baseline to 4–6 weeks after surgery between patients with impaired and normal olfaction scores, at various levels of baseline cognitive Z-score. Presented p-values are associated with the adjusted comparison of change in composite cognitive score for impaired vs. normal olfaction groups, at several selected levels of baseline cognition.