Associations Between Daytime Napping, Sleep Duration and Postoperative Delirium

Postoperative delirium (POD) is a common occurrence for patients in the postanaesthesia care unit (PACU) or intensive care units. A growing body of literature suggests sleep habits may be related to one's risk of developing delirium. However, these sleep habits have yet to be objectively measured via actigraphy during a lengthy follow-up. We analysed 6 days of actigraphy data collected from 54,845 UK Biobank participants who had at least one hospitalisation during an 8-year follow-up. Nap duration (sleep between 9 AM and 7 PM), nap frequency, overnight sleep duration (between 7 PM and 9 AM) and wake after sleep onset (WASO) were examined from actigraphy data. Cox proportional hazards models analysed whether these objective sleep behaviours predicted POD risk. Nappers were at an increased risk of POD development for every additional 30 min (HR = 1.15; 95% CI: [1.06-1.25], p < 0.001) of napping and for every additional nap (1.13 [1.05-1.21], p < 0.001) per day. Those who recorded ≥ 9 h of overnight sleep (1.19; [0.70-2.02.], p = 0.521) or < 6 h of overnight sleep (1.15; [0.84-1.57], p = 0.381) showed no significant increase in POD risk compared to 6-9-h overnight sleepers. There was no significant increased risk in POD for each additional minute of WASO (1.00; [1.00-1.00], p = 0.463). We conclude that napping is associated with an increased risk for POD development. Whether napping is a controllable factor that can limit POD development or a symptom of a more significant cognitive pathology is still unknown. Further studies are required to understand the relationship between napping and cognitive insult.