Wrist Actigraphy and Sleep Diaries

Actigraphy can provide unique information regarding temporal interrelations between sleep and pain, and has become a leading modality to assess the state of sleep and objective INS. While not appropriate for the diagnosis of sleep-disordered breathing or PLMs, multiday actigraphy is highly appropriate for examining nightly variability in INS of patients in their home environment, with their regular habits and routine. Reduced night-to-night variability obtained from actigraphy can reflect improved sleep stability and be an objective measure of sleep quality. In addition, actigraphy is useful to investigate individual preferences regarding sleep and waking times, which is hypothesized to be a behavioral manifestation of underlying circadian rhythms. Morningness (early sleep timing) and eveningness (late sleep timing) are the extremes of these individual preferences.

An actigraph is a wristwatch-like device loaded with a miniaturized acceleration sensor^25–27 that quantifies physical motions. The resulting sleep-wake pattern of actigraphy shows sleep status including sleep onset time, considered as 10 consecutive minutes of no arm movement (hour and minutes), and sleep offset time (hour and minutes). Time in bed was considered as sleep duration plus awakenings, from initial sleep onset to sleep offset (in minutes); sleep duration was the total amount of sleep without awakenings (in minutes); sleep efficiency was calculated as sleep duration divided by time in bed (as a percentage); sleep latency was measured as the time between bedtime and falling asleep (in minutes); and wake after sleep onset (WASO) was the time spent awake between initial sleep onset and final sleep offset (in minutes).²⁸ Sleep episodes were defined as awakenings that lasted for at least 1 minute.

The actigraph (Motionlogger Watch, Ambulatory Monitoring, Inc., United States) was worn on the non-dominant wrist (de Souza et al.²⁹) by the participants, concurrently with the completion of sleep diaries,^26,29 to provide a behavioral assessment in their home environment.

Actigraphy data were collected in 1-minute sampling epochs, using the zero-crossing mode,²⁹ and sleep-wake variables were calculated using the Motionlogger WatchWare software 1.45.0.5 (Ambulatory Monitoring Inc., United States). The analyses were performed using ActionW 2.6 software (Ambulatory Monitoring Inc.) by a blinded investigator (CF).

Participants were requested to wear the actigraph for 10 consecutive days, only removing it during bathing. Participants were instructed to push the event button at bedtime and wake time to create a marker in the data to be scored. Sleep diaries were used to set the parameters for total time in bed in the actigraphy software. When the participant did not push the event button, sleep onset/offset was considered to occur after 10 minutes of no arm movement from the time recorded in the sleep diary.²⁹

Actigraphy has been validated by demonstrating its agreement with polysomnographic recordings.^25,30 About 5 to 7 nights are considered reliable for estimating total sleep time.³¹ We used 10 days to compare weekdays and weekends. All variables related to sleep were calculated using the Cole-Kripke algorithm.³² The number of episodes of sleep was not included in the ActionW software package; this was calculated using the SPSS 18 package.