Academic journal article Journal of Nursing Measurement

Nighttime Variability in Wrist Actigraphy

Academic journal article Journal of Nursing Measurement

Nighttime Variability in Wrist Actigraphy

Article excerpt

Wrist actigraphy measures sleep activity and circadian rhythm. This study examined nighttime variability in Actiwatch parameters in a sample of breast cancer survivors (BCSs) to determine a minimum number of nights needed to obtain an accurate picture of objective sleep. A descriptive, quantitative, and repeated measures design was used. Consenting participants wore an actigraph and completed a sleep diary across 7 nights. There were no significant differences in wake after sleep onset (WASO), total sleep time (TST), sleep latency, or sleep disturbances across nights of week (Monday to Sunday) or monitoring nights (1st to 7th). Sleep efficiency was significantly better at Night 6 compared with Night 7. The coefficients of variation (CVs) for WASO ranged from 46% to 86%, TST 23%-34%, sleep latency 154%-246%, sleep efficiency 12%-22%, and sleep disturbances 33%-41%. Although the CVs indicated high variability across women, there was little internight variability in WASO or TST during across 7 nights of sleep. This suggests that in BCSs, Actiwatch data could be collected and evaluated from any single night for an accurate measure of usual sleep.

Keywords: sleep; actigraphy; breast cancer; circadian rhythm; survivors

Wrist actigraphy is a valuable measure of sleep activity and circadian rhythms. The device, which typically looks like a sports watch, is worn on the nondominant wrist for 1 or more nights to measure nighttime sleep (Mini Mitter Co., Inc., 2003). Although not used for diagnosis of clinical sleep disorders, actigraphy is used as a research tool in various patient populations to assess number of sleep disturbances, time spent in bed asleep, and sleep latency (Jean-Louis et al., 1996; Jean-Louis et al., 1997a, 1997b). Researchers evaluating sleep in patients with cancer and cancer survivors have used actigraphy to provide descriptive information about sleep and circadian patterns and to test efficacy of interventions (Ancoli-Israel et al., 2005; Berger, Farr, Kuhn, Fischer, & Agrawal, 2007; Berger et al., 2002; Berger et al., 2003; Epstein & Dirksen, 2007; Miaskowski & Lee, 1999; Roscoe et al., 2002).

Although there are recommendations for using wrist actigraphy to study sleep and circadian rhythms (Littner et al., 2003), these recommendations do not specify the optimal number of monitoring nights needed to accurately measure sleep patterns. Some researchers use 6-7 nights (Berger et al., 2002; Epstein & Dirksen, 2007), whereas others use only 2-3 nights (Ancoli-Israel et al., 2005; Berger et al., 2007; Miaskowski & Lee, 1999; Roscoe et al., 2002). It is unclear if nighttime actigraphy data such as wake after sleep onset (WASO), total sleep time (TST), sleep efficiency, sleep latency, and numbers of sleep disturbances are consistent or variable within a week of monitoring. Knowing this information would be useful for making recommendations for a minimum number of nights needed to obtain an accurate picture of nighttime sleep activity. Thus, the purpose of this study was to examine nighttime variability in common actigraphy outcome variables, WASO, TST, sleep efficiency, sleep latency, and number of sleep disturbances in a sample of breast cancer survivors (BCSs) to determine if there is a minimum number of nights needed to obtain an accurate picture of objective sleep.

BACKGROUND

Sleep disturbances in patients with cancer have received recent attention in both descriptive and intervention research studies (Ancoli-Israel et al., 2005; Berger, 1998; Berger et al., 2003; Epstein & Dirksen, 2007; Miaskowski & Lee, 1999; Roscoe et al., 2002; Young-McCaughan et al., 2003). To operationalize objective sleep patterns, researchers often use one of two types of objective sleep monitoring: polysomnography or wrist actigraphy. Polysomnography is considered the gold standard for objective sleep measurement. Polysomnography includes at least one overnight stay in a sleep laboratory where electrodes are placed on the face, head, and chest measuring the different phases of sleep (Bowman & Moshenin, 2003). …

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