Wearable-derived first-night postoperative sleep disturbance and delirium in older emergency abdominal surgery patients: a prospective pilot study

Postoperative delirium (POD) is common in older patients after emergency abdominal surgery and may be related to early postoperative sleep disruption. We explored whether wearable-derived sleep parameters during the first postoperative night were associated with POD. This prospective pilot observational study enrolled patients aged ≥ 60 years undergoing emergency abdominal surgery between 1 September 2025 and 1 March 2026. Sleep during the first postoperative night was monitored using a medical-grade multisensor wearable system that recorded electrocardiography, respiratory movement, and accelerometry signals and generated algorithm-derived sleep parameters. Monitoring was initiated after postoperative transfer to the general surgery ward and continued during the first postoperative night. Sleep parameters included total sleep time, sleep efficiency, algorithm-derived arousal index, algorithm-derived N3 sleep, algorithm-derived REM sleep, and an exploratory light-sleep predominance index. POD was assessed during the first postoperative week using the Richmond Agitation–Sedation Scale followed by the Confusion Assessment Method for the ICU in arousable patients. POD was defined as at least one positive CAM-ICU assessment during postoperative days 1–7. The temporal relationship between completion of sleep monitoring and the first positive delirium assessment was reviewed. Associations between sleep parameters and POD were evaluated using Firth penalized logistic regression. Limited adjusted models included age and postoperative SOFA score. Twenty-three patients were included in the final complete-case analysis, of whom 10 developed POD. POD occurred in 10 of 23 analyzed patients (43.5%); this proportion describes the selected pilot cohort and should not be interpreted as a population-level incidence estimate. No patient had a positive CAM-ICU assessment before or during first-night sleep monitoring. Compared with patients without POD, patients who developed POD had shorter total sleep time (median, 260.0 vs. 312.0 min; P = 0.008), lower sleep efficiency (53.5% vs. 62.0%; P < 0.001), and a higher algorithm-derived arousal index (28.25 vs. 20.90 events/h; P < 0.001). They also had lower algorithm-derived N3 and REM sleep values and a higher light-sleep predominance index (all descriptive P values ≤ 0.002). In univariable Firth models, total sleep time and the other prespecified sleep parameters were associated with POD. After adjustment for age and postoperative SOFA score, none of the associations remained statistically significant, and confidence intervals were wide. In this small exploratory pilot study, postoperative delirium was associated with worse wearable-derived sleep continuity and sleep architecture during the first postoperative night in unadjusted analyses. Larger studies with comprehensive perioperative covariate assessment and validation against reference sleep measures are needed.