Invalidity of one actigraphy brand for identifying sleep and wake among infants

Study objectives: Few commercially available brands of actigraphs (ACT) have been subjected to rigorous validation with infant participants. The purpose of this study was to examine the agreement between concurrent polysomnography (PSG) and one brand of ACT (AW-64, Mitter Co. Inc.) using appropriate statistical techniques among a sample of healthy infants.

Methods: Twenty-two healthy infants (14.1+/-0.6 months) had one night of ankle ACT recording during research PSG at Kosair Children's Hospital Sleep Research Center in Louisville, Kentucky. Macroanalyses were conducted using the Bland-Altman concordance technique to assess agreement between total sleep time (TST) and wake after sleep onset (WASO) simultaneously measured by PSG and ACT, using two ACT algorithm settings. Microanalyses were also calculated to examine sensitivity, specificity, and accuracy of ACT within each PSG-identified sleep state. Correlations were calculated between PSG-identified arousals and the discrepancies between ACT and PSG.

Results: The Bland-Altman concordance technique revealed that ACT underestimated TST by 72.25 (SD=61.48) minutes and by > or = 60 min among 54.55% of infants. Furthermore, ACT overestimated WASO by 13.85 (SD=30.94) minutes and by > or = 30 min among 40.91% of infants. Sensitivity, specificity, and accuracy analyses revealed that ACT adequately identified sleep, but poorly identified wake. PSG and ACT discrepancies were positively associated with PSG-identified arousals (r=.45).

Conclusions: Improved device and/or software development is needed before the AW-64 can be considered a valid method for identifying infant sleep and wake.