Rest-activity rhythmicity as digital biomarkers of postoperative recovery and complications in children

Surgery and postoperative complications disrupt circadian rhythms. While clinicians recognize the implicit value of circadian rhythms to evaluate postoperative recovery, the absence of a practical means to measure them has limited their exploration and integration into clinical practice in children.

Consumer wearable device (Fitbit) was given to children 3-18 years old who underwent laparoscopic appendectomy for complicated appendicitis and data were collected during postoperative days (POD) 1 to 21. Three novel rest-activity rhythmicity (RAR) metrics were computed from minute-by-minute continuous Fitbit data: (1) Periodicity and (2) Amplitude of the 24-hour Activity Rhythm; and (3) Circadian quotient of the 24-hour heart rate (HR) Rhythm. RAR trajectories were aggregated for patients without postoperative complications and compared against trajectories for patients with complications.

Ninety-four patients were included in the analysis (n=13 [14%] with complications). For patients without complications, three RAR metrics gradually increased in intensity until reaching plateaus between POD 11-20 (Periodicity of the 24-hour Activity Rhythm, 95% confidence interval [CI]: POD 9-14; Amplitude of the 24-hour Activity Rhythm, 95% CI: POD 16-24; Circadian quotient of the 24-hour HR Rhythm, 95% CI: POD 9-15). Although the RAR metrics for children with complications increased in intensity, none plateaued during the 21-day study period.

Wearable-derived circadian rhythms demonstrated distinct patterns in RAR metrics for children with and without complications during the 21-day study period following appendectomy. This suggests that the RAR may be relevant digital biomarkers to track postoperative recovery and identify complications in pediatric populations.