Examination of wrist and hip actigraphy using a novel sleep estimation procedure

• Published in: Sleep science (São Paulo, SP ) SP ), 2014-06, Vol.7 (2), p.74-81
• Main Authors: Ray, Meredith A., Youngstedt, Shawn D., Zhang, Hongmei, Robb, Sara Wagner, Harmon, Brook E., Jean-Louis, Girardin, Cai, Bo, Hurley, Thomas G., Hébert, James R., Bogan, Richard K., Burch, James B.
• Format: Article
• Language: English
• Subjects: Actigraphy; Original; Penalized spline; Polysomnography
• ISSN: 1984-0063; 1984-0659; 1984-0063
• DOI: 10.1016/j.slsci.2014.09.007

Objective: Improving and validating sleep scoring algorithms for actigraphs enhances their usefulness in clinical and research applications. The MTI® device (ActiGraph, Pensacola, FL) had not been previously validated for sleep. The aims were to (1) compare the accuracy of sleep metrics obtained via wrist- and hip-mounted MTI® actigraphs with polysomnographic (PSG) recordings in a sample that included both normal sleepers and individuals with presumed sleep disorders; and (2) develop a novel sleep scoring algorithm using spline regression to improve the correspondence between the actigraphs and PSG. Methods: Original actigraphy data were amplified and their pattern was estimated using a penalized spline. The magnitude of amplification and the spline were estimated by minimizing the difference in sleep efficiency between wrist- (hip-) actigraphs and PSG recordings. Sleep measures using both the original and spline-modified actigraphy data were compared to PSG using the following: mean sleep summary measures; Spearman rank-order correlations of summary measures; percent of minute-by-minute agreement; sensitivity and specificity; and Bland–Altman plots. Results: The original wrist actigraphy data showed modest correspondence with PSG, and much less correspondence was found between hip actigraphy and PSG. The spline-modified wrist actigraphy produced better approximations of interclass correlations, sensitivity, and mean sleep summary measures relative to PSG than the original wrist actigraphy data. The spline-modified hip actigraphy provided improved correspondence, but sleep measures were still not representative of PSG. Discussion: The results indicate that with some refinement, the spline regression method has the potential to improve sleep estimates obtained using wrist actigraphy.