Effects of morning versus afternoon surgery on peri-operative disturbance of sleep-wake timing: An observational study

Introduction: The circadian timing system regulates diurnal sleep-wake rhythm. Previously, we showed that, in patients undergoing elective surgery, sleep-wake timing is altered and post-operative sleep quality is reduced. However, how the timing of the surgical procedure affects the disturbance and what other factors affect this disturbance remain unknown.

Methods: Single-centre prospective observational study investigating the influence of surgery timing on post-operative sleep in adult patients (≥18 years) undergoing elective surgery. Sleep-wake timing was measured from three nights before until seven nights after surgery with a daily sleeping log. Primary outcome was post-operative midpoint of sleep shift between patients undergoing morning and afternoon surgeries. Secondary outcomes included factors affecting sleep timing disturbance and changes in subjective sleep quality.

Results: We included 259 patients: 144 patients underwent morning procedures (08:00 h-12:00 h) and 115 underwent afternoon procedures (12:00 h-17:00 h). Both groups had significant phase advance of midpoint of sleep on the night after surgery when compared with three nights before surgery (mean - 00:41 h, 95% CI -00:27 h to -00:54 h, p < .001, for morning surgery and mean - 00:28 h, 95% CI -00:09 h to -00:46 h, p = .003, for afternoon surgery). However, there was no between-group difference (mean - 00:13 h, 95% CI -00:35 h-00:09 h, p = .25). Reduction of sleep quality was also similar. Phase advance was larger for patients with an evening chronotype or with lower pre-operative sleep quality. Decline of sleep quality after surgery was larger for patients with an evening chronotype, longer procedures or better pre-operative sleep quality.

Conclusion: Our results suggest that the timing of surgery between 08:00 h and 17:00 h does not modulate the effect of anaesthesia and surgery on phase of the sleep-wake rhythm in patients undergoing elective surgery with a low pre-operative risk of delirium.

Editorial comment: Timing of surgery may impact post-operative sleep. However, in this prospective cohort study of elective surgical patients, sleep-wake timing and post-operative sleep quality did not differ between those undergoing morning versus afternoon surgery.