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1. Actigraphy Assessment of Mother’s Sleep: 6, 12 & 18 weeks postpartum Janelle MacKenzie, Kerry Armstrong & Simon Smith Introduction: Method: Mothers’ sleep during the postpartum period is often characterised by numerous sleep bouts across the night, resulting in low sleep efficiency and increased daytime sleepiness. Mothers’ sleep quantity is often reported as total sleep time, with some studies suggesting that new mothers obtain sleep duration similar to that obtained by the general population. Understanding of the nature of mothers’ sleep needs to incorporate indices of both sleep quantity, such as total sleep time, and sleep quality, such as sleep efficiency and activity levels during sleep bouts. Subjective measures of sleep, such as sleep diaries, have been used with this population with uncertain utility; however, only a small number of studies have documented objective sleep (with actigraphy) in this population. This longitudinal study aimed to objectively measure mothers’ sleep during the first 18 weeks postpartum, to ascertain the nature and magnitude of sleep disturbance experienced. Eleven mothers (Mean age = 29.82, SD = 4.45) from Australia wore Actiwatch-2 devices for up to 7 days and nights at 6, 12 and 18 weeks postpartum. For each night of recording, a number of discrete sleep bouts (SB) were identified. Total sleep time (TST) was calculated as the total number of minutes across the night within these bouts. Sleep efficiency (SE) was calculated as the percentage of minutes across the night classified as being part of a sleep bout, with higher scores indicating higher efficiency. Sleep quality(SQ) captured the efficiency of sleep within sleep bouts, and was calculated as the percentage of epochs classified as sleep within sleep bouts, with higher scores indicating higher sleep quality. Figure 1. Calculation of sleep metrics during a night with three sleep bouts TIB SB1 SB2 SB3 sq1: % of epochs classified as SLEEP sq2 sq3 SB1 + SB2 + SB3 SE = SQ = mean( sq1 + sq2 + sq3) TST = SB1 + SB2 + SB3 % TIB Results: Total sleep time was accumulated from a number of sleep bouts throughout the course of a night for the majority of mothers during each assessment period. At 6 weeks postpartum, mean sleep quality was 93.15% (SD = 2.68) and scores did not significantly change across the assessment periods. Table 1. Descriptive statistics for TST and SB While there was no relationship between sleep efficiency and sleep quality during weeks 6 and 12, a significant positive relationship was observed at week 18, r2=.52, p =.013. Sleep Efficiency Sleep Quality Note. TST = mins. per night; SB = no. per night. Total sleep time did not significantly differ across the assessment periods, however there was a trend towards an increase over time. Sleep efficiency increased across the time periods (F(2,10) = 10.30, p = .001), with a significant increase between week 12 and week 18. Figure 2. Means and SDs for SE and SQ by assessment week Conclusion: At 6 weeks postpartum, mean TST was 420.21 minutes (SD = 50.61) and gradually increased over the subsequent assessment periods, equating to 7 or more hours a night. Within this sample, only a low level of disruption was consistently shown within the mothers’ night time sleep bouts. However, overall sleep efficiency suggested a significant proportion of time spent awake between sleep bouts. The significant positive relationship between SE and SQ at 18 weeks postpartum suggests that mothers that are spending less time awake between sleep bouts are sleeping better during their sleep bouts. While TST remained stable over time, overall sleep efficiency improved, suggesting the mothers’ sleep was becoming more consolidated. However, a single sleep bout a night was not often experienced during any of the assessment periods.