Consumer wearables, such as smart watches, are a promising tool for monitoring circadian health in "real world" settings. Bowman et al. demonstrate that circadian signals can be accurately captured through heart rate data obtained from wearables, opening up new possibilities for population-level studies on heart rate and circadian rhythm.

Taking the time for our bodies: How wearables can be used to assess circadian physiology

Night shift work, characterized by behavioral circadian disruption, increases cardiometabolic disease risk. Our long-term goal is to develop a novel methodology to quantify behavioral circadian disruption in field-based settings and to explore relations to four metabolic salivary biomarkers of circadian rhythm. This pilot study enrolled 36 police academy trainees to test the feasibility of using wearable activity trackers to assess changes in behavioral patterns. Using a two-group observational study design, participants completed in-class training during dayshift for six weeks followed by either dayshift or nightshift field-training for six weeks. We developed a novel data-post processing step that improves sleep detection accuracy of sleep episodes that occur during daytime. We next assessed changes to resting heart rate (RHR) and sleep regularity index (SRI) during dayshift versus nightshift field training. Secondarily, we examined changes in field-based assessments of salivary cortisol, uric acid, testosterone, and melatonin during dayshift versus nightshift. Compared to dayshift, nightshift workers experienced larger changes to resting heart rate, sleep regularity index (indicating reduced sleep regularity), and alternations to sleep/wake activity patterns accompanied by blunted salivary cortisol. Salivary uric acid, testosterone, and melatonin did not change. These findings show that nightshift work--a form of behavioral circadian rhythm disruption--was detectable in police trainees using activity trackers alone and in combination with a specialized data analysis methodology. KEY POINTSO_LINight shift work increases cardiometabolic disease risk and this may be a consequence of behavioral circadian misalignment. C_LIO_LITo advance this hypothesis, methodologies to quantify behavioral irregularities during nightshift in field-based settings are needed. C_LIO_LIIn this pilot study, commercially available activity trackers combined with a novel data processing step were used to assess alterations in sleep/wake patterns in police trainees during dayshift versus nightshift. C_LIO_LIWe also explored relations with four metabolic salivary biomarkers of circadian rhythm during dayshift versus nightshift. C_LIO_LICompared to dayshift, nightshift resulted in larger perturbations of resting heart rate, sleep regularity index (indicating reduced regularity), and alterations in sleep and activity patterns; this was accompanied by blunted cortisol. C_LIO_LIThis novel data processing step extends commercially available technology for successful application in real-world shift work settings. C_LI

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M. Erickson

Papers

Assessing the Effects of Behavioral Circadian Rhythm Disruption in Shift-Working Police Academy Trainees