Actigraphy vs Polysomnography measurements for sleep arousals
Authors: Paige Little Judith , Ho Selina , Rayward Lionel , Uhrle Glenice , Green Daniel , Pearcy Mark 
Published: June 2022

This study sought to better understand how actigraphy may be practically applied to interpret useful information about sleep arousals when used in future studies of home-based sleep. For this purpose, we analysed a small cohort of healthy adult’s sleep using polysomnographic (PSG) measurements and actigraphy.Significance: Used to evaluate objective measure of motility and rest, actigraphy is commonly applied to assess physiological sleep parameters. While PSG recordings of sleep physiology have been shown to provide high fidelity measurements of key sleep parameters, the portability, ease of set-up, and low participant burden make actigraphy advantageous for measuring sleep parameters over extended nights of home-based sleep. Despite the ready uptake of actigraphy for clinical sleep assessments, this modality has lower accuracy in detecting periods of wake (AW) and a high magnitude of false positives when detecting sleep [1]. Methods: Ten healthy adults (50% male:female, mean age 25.9±3.2 years) with no history of sleep pathology took part in the study over four/five nights of sleep. To remove confounding aspects related to sleep pathologies/co-morbidities, healthy participants were studied. Participants were provided with an Actiwatch Spectrum Pro (Phillips Respironics Inc) to wear nightly on their non-dominant (in all cases left) wrist. Actiware (V6.0.9) was utilised to collate, and score the actigraphy measurements, with all 15-second epochs scored as either ‘wake’ or ‘sleep’, and a pre-set activity threshold (‘medium’) selected on the basis of preliminary testing.At the same time, the participant underwent ambulatory PSG using a Nox A1 (Nox Medical) PSG system. This is a portable polysomnography device used in our local sleep clinic to capture in-home PSG metrics. Sleep metrics from the Nox A1 were scored visually by a highly experienced, clinical sleep technician using the Noxturnal Software System (Vsn 6.0, Nox Medical), according to international scoring guidelines. Scoring was based on 15-second epochs and arousals lasting longer than this were considered ‘wake’. Analysis for this study focussed on comparison of arousal counts from PSG and actigraphy using Pearson linear correlation.Discussion of Results: A total of 41 nights of sleep measurements were collected. To better understand the relationship between PSG- and actigraphy-measured arousals, and mindful that the Actiwatch was worn on the left arm, customised arousal scoring for: 1) AA arousals (all scored physiological arousals); 2) LMA arousals (only physiological arousals that included a left arm movement); were scored. Spearman correlation analysis showed a significant, low-strength, positive relationship (rho=0.314, p=0.045) between PSG AA and Actiwatch awakenings, and sensitivity and specificity were calculated as 97% and 37%, respectively when comparing LMA with awakenings. However, a significant, high-strength, positive relationship (rho=0.660, p<0.001) was observed between PSG LMA and Actiwatch awakenings with increased specificity of 58%. This strong agreement between LMA arousals and actigraphy awakenings highlighted the utility of actigraphy in measuring sleep related arousals, although caution is needed when interpreting physiological ‘body-related’ awakenings vs limb-related motility associated with physiological awakenings. The low user cost associated with actigraphy for long-term home-based sleep studies, makes it a preferred alternative to PSG, and study results will assist to interpret actigraphy-based data in future studies of other populations.[1] Paquet et al, 2007. Sleep, 30(10), 1362-1369