Actimetry in infant sleep research: an approach to facilitate comparability

Abstract

Study ObjectivesOnly standardized objective assessments reliably capture the large variability of sleep behavior in infancy, which is the most pronounced during the human lifespan. This is important for clinical as well as basic research. Actimetry is a cost-efficient method to objectively track infant sleep/wake behavior by assessing limb movements. Nevertheless, the standardization of actimetry-based sleep/wake measures is limited by two factors: the use of different computational approaches and the bias towards measuring only nighttime sleep - neglecting [~]20 % of sleep infants obtain during daytime.\n\nMethodsWe used actimetry in 50 infants for 10 continuous days at ages 3, 6 and 12 mo in a longitudinal approach. We analyzed the infants sleep/wake behaviors applying with two commonly used algorithms: Sadeh and Oakley/Respironics. We compared minute-by-minute agreement and Kappa between the two algorithms, as well as the algorithms with sleep/wake measures from a comprehensive 24-hour, parent-reported diary.\n\nResultsAgreement between uncorrected algorithms was moderate (77 - 84%). By introducing a 6-step adjustment, we increased agreement between algorithms (96 - 97%) and with the diary. This decreased the difference between the two algorithms in e.g. Total Sleep Duration from 4.5 h to 0.2 h.\n\nConclusionsThis computational pipeline enhances comparability between infant actimetry studies and the inclusion of parent-reported diaries allows the integration of daytime sleep. Objectively assessed infant sleep that is comparable across different studies supports the establishment of normative developmental trajectories and clinical cutoffs.