I read the report by Marmis et al1 with great interest. The authors examined the relationship between a wrist accelerometer, the Actiwatch-2 (Philips Co. Ltd., United Kingdom), and the Consensus Sleep Diary to check concurrent validity in career firefighters. Firefighters overestimated sleep efficiency and underestimated wake after sleep onset in the sleep diary, and there were large disagreements between the 2 sleep monitoring methods. Regarding concurrent validity of self-reported and accelerometer-derived sleep, I have a comment on the validity of accelerometers for detecting sleep parameters.
Liu et al2 compared 2 devices based on the mechanism of an accelerometer to check the agreements of several sleep parameters. There were discrepancies in some sleep parameters, and the GT9X Link (ActiGraph Co. Ltd., Pensacola, Florida) presented longer wakefulness after sleep onset and a higher sleep fragmentation index by setting Actiwatch-2 as a standard method. In contrast, total sleep time and sleep efficiency presented good agreements. Cellini et al3 also compared sleep parameters and physical activity between GT3X+ (ActiGraph Co. Ltd., Pensacola, Florida) and Actiwatch-64 (Philips Co. Ltd., United Kingdom). Although the GT3X+ showed high agreement for total sleep time and sleep efficiency by setting the Actiwatch-64 as a standard, wakefulness after sleep onset and sleep onset latency were underestimated. Unfortunately, sleep polysomnography was not measured in these studies. I agree that intraclass correlation coefficients and Bland–Altman plots present a level of agreement on each sleep parameter from different apparatuses, but Actiwatch cannot become a gold standard for sleep parameters. Although Lee and Suen4 reported that Actiwatch-2 is a validated accelerometer, each sleep parameter sometimes requires a different threshold setting for Actiwatch, which also depends on the characteristics of participants and their sleep disorders.5
DISCLOSURE STATEMENT
Work for this study was performed at Nippon Medical School. The author reports no conflicts of interest.
Citation: Kawada T. Wrist accelerometer and sleep diary in career firefighters: a validation study. J Clin Sleep Med. 2024;20(8);1399.
REFERENCES
- 1. Marmis R , McGoldrick-Ruth L , Kelly MR , Haynes PL . Comparing actigraphy and diary to measure daily and average sleep in firefighters: a Bland–Altman analysis . J Clin Sleep Med. 2024. ; 20 ( 4 ): 497 – 503 . [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2. Liu F , Schrack J , Wanigatunga SK , et al . Comparison of sleep parameters from wrist-worn ActiGraph and Actiwatch devices . Sleep. 2024. ; 47 ( 2 ): zsad155 . [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3. Cellini N , McDevitt EA , Mednick SC , Buman MP . Free-living cross-comparison of two wearable monitors for sleep and physical activity in healthy young adults . Physiol Behav. 2016. ; 157 : 79 – 86 . [DOI] [PMC free article] [PubMed] [Google Scholar]
- 4. Lee PH , Suen LK . The convergent validity of Actiwatch 2 and ActiGraph Link accelerometers in measuring total sleeping period, wake after sleep onset, and sleep efficiency in free-living condition . Sleep Breath. 2017. ; 21 ( 1 ): 209 – 215 . [DOI] [PubMed] [Google Scholar]
- 5. Kawada T , Suzuki H , Shimizu T , Katsumata M . Agreement in regard to total sleep time during a nap obtained via a sleep polygraph and accelerometer: a comparison of different sensitivity thresholds of the accelerometer . Int J Behav Med. 2012. ; 19 ( 3 ): 398 – 401 . [DOI] [PubMed] [Google Scholar]