Actigraphic assessment of a polysomnographic-recorded nap: A validation study

University of California, San Diego - Department of Psychiatry Veterans Affairs, San Diego, CA, USA.
Journal of Sleep Research (Impact Factor: 3.35). 03/2011; 20(1 Pt 2):214-22. DOI: 10.1111/j.1365-2869.2010.00858.x
Source: PubMed


This study aimed to determine if actigraphy could differentiate sleep and wake during a daytime nap and no-nap rest period. Fifty-seven subjects participated in the study; 30 subjects were in the nap group and the remaining 27 in the no-nap comparison group. All subjects wore actigraphs while simultaneously undergoing polysomnography (PSG). Three actigraphic sensitivity levels (high, medium, low) and two interval duration minimums (15 and 40 min) were used to score the nap and no-nap data. The variables examined included total sleep time (TST), sleep latency (SL), wake after sleep onset (WASO) and sleep efficiency (SE). The Bland-Altman technique was used to determine concordance. Epoch-by-epoch analysis examined actigraphic accuracy, sensitivity and specificity. For the naps, all actigraph settings except low-40 showed significant correlations with TST. The high and medium settings predicted SE significantly and the high settings predicted SL significantly. Bland-Altman analyses demonstrated high settings overestimated TST while high and medium settings overestimated SE. Overall, for the nap condition accuracy for the actigraph was 82-86%, sensitivity was 92-96% and specificity was 40-67%. In the no-nap condition, accuracy for the actigraph was 60-84%, sensitivity was 47-78% and specificity was 60-86%. Medium-40 and low-40 were the only settings that did not misidentify sleep in the no-nap condition. These results suggest that actigraphy can predict TST, SE and SL reliably, depending upon parameter settings, and actigraphy is a highly sensitive but not specific measure for daytime naps. Different actigraphy settings may be optimal depending upon the variables of interest. Discrimination of sleep and wake during periods of waking quiescence is not as robust as during periods of mainly daytime sleep.

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    • "The use of actigraphy to assess daytime sleep has been validated previously in healthy subjects in both the laboratory and community setting [37,38] and the measurement of daytime sleep-wake disturbance in this study was conducted according to previously established protocols [46,52]. Following clinical assessment, participants were required to wear a wrist actiwatch (Minimitter Actiwatch Spectrum) on the wrist less affected by tremor every day for fourteen days. "
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    • "The aim of this study was to directly compare two widely used actigraph devices, Actiwatch-64 (AW-64; Phillips Respironics, Bend, Oregon, USA) and the GT3Xþ (Actigraph, Pensacola, Florida, USA), with a PSG-recorded nap. AW-64 is commonly used in sleep research (Meltzer & Westin, 2011) and has been validated both for nocturnal sleep (Rupp & Balkin, 2011) and daytime naps (Kanady et al., 2011). The GT3Xþ is regularly used to measure daytime activity (Rowlands & Stiles, 2012), but it also provides the possibility to record and score sleep/wake patterns. "
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    • "Subjects filled out sleep diaries and wore actigraph wristwatches (Actiwatch- 64, Respironics) as subjective and objective measures of sleep–wake activity, respectively. All of the naps self-reported in sleep diaries were verified by actigraphy, which has been validated to reliably predict TST, SE, and sleep latency (SL) of daytime naps [14]. Actigraphy data were scored using Respironics Actiware version 5.52.003 software . "
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