Introduction:: Pregnancy is associated with significant structural (e.g. decreased brain size) and functional (e.g. increased reactivity) changes [1], [2]. These profound changes are the result of biologic (e.g. hormone changes), ecologic (e.g. changing environmental demands to prepare for nurturing a baby), and other factors [3]. Due to the complexity and substantiveness of these biological and environmental changes that lead to motherhood, this period of life is often compared to the profound changes that occur during adolescence. In addition, some consider this period its own neurocognitive developmental stage (sometimes called matrescence) [3]. During this developmental stage individuals commonly report cognitive changes, such as changes to memory and mood (i.e., so-called ‘pregnancy brain’) [4]. These cognitive changes have been associated with subjective sleep quality [3], which is commonly disrupted during pregnancy [5]. However, use of objective methods to quantify sleep changes in pregnancy are limited [6], and only a few longitudinal studies have been performed [7]–[11]. Only one of these studies included pre-pregnancy sleep data [9]. Sleep stages have been linked to various memory mechanisms, and further study may provide insight into this important neurodevelopmental stage of life [12]. Therefore, the purpose of this report is to describe changes in sleep stages throughout the perinatal period in a single case report. These data were collected before, during, and after pregnancy using a wearable headband sensor that monitors brain activity during sleep [13].
Materials and Methods:: Data Collection: Case data was provided by a member of the lab who was testing a wearable sleep sensor (DREEM 2 headband) [13] for a different project before her pregnancy, then out of interest continued to use the sensor during and after her pregnancy. The DREEM 2 headband is worn around the head at night and collects physiologic data, including brain activity via EEG, movement and posture via an accelerometer, and heart rate via a pulse oximeter. The DREEM 2 algorithm scores sleep data providing sleep stage information that is comparable to the gold standard PSG [13]. Five nights of data collection were available before pregnancy, 16 during, and 2 following. This case report data were collected out of interest of the lab member, therefore it is exempt from Research Ethics Board (REB) review. Permission to use the data was obtained from the lab member.
Data Analysis: sleep reports were downloaded from the DREEM portal and analyzed in Matlab (MathWorks, Inc. (2022)). Sleep is divided into rapid eye movement (REM) sleep and non-REM (NREM). NREM sleep is further divided into stages 1-3. Stage 3 is also referred to as slow wave sleep (SWS) and represents the deepest level of sleep. A one-way ANOVA was used to compare the perinatal period on sleep stage percentage of total sleep time. A linear regression model was used to test if day of pregnancy predicted sleep stage percentage of total sleep time.
Results, Conclusions, and Discussions:: We found significant changes for NREM stages 2 and 3, and REM sleep (see Figure 1). Post-hoc analysis revealed that percentage NREM stage 2 in trimester 1 (T1), trimester 2 (T2), and trimester 3 (T3) were all significantly higher than pre-pregnancy. Post-pregnancy NREM stage 2 percentage was significantly lower compared to T3. Percentage NREM stage 3 in T1 was significantly higher compared to T3. Percentage REM sleep was significantly higher pre-pregnancy compared to T1, T2, and T3. Simple linear regression was used to test if days of pregnancy predicted sleep stage percentage for each of the sleep stages (see Figure 2). The regression was statistically significant for NREM stage 2 (p = 0.026) and NREM stage 3 (p = 0.041). Day of pregnancy explained 25.9% and 21.4% of the variation in stage 2 and stage 3 sleep, respectively.
Our results agree with previous literature [7]–[11], which found the following in the perinatal period: no change in percentage of NREM stage 1 sleep, percentage of NREM stage 2 increases through pregnancy but may drop postpartum, and percentages of NREM stage 3 and REM sleep decrease during pregnancy. Only one of these prior studies monitored sleep prior to pregnancy [9]. In this prior study only 1 night before, 3 nights during, and 2 nights after pregnancy were analyzed, 7 total. Ease-of-use allowed 23 nights to be collected with DREEM 2 in this case report, which as shown by Figure 2 allows the variability in sleep across pregnancy to also be visualized.
Wearable sensors are a feasible tool to longitudinally monitor sleep changes in the perinatal period. Sleep monitoring allows further investigation of brain changes during this important neurocognitive developmental stage [3]. Sleep changes may be associated with changes in levels of gray matter volume [14], memory systems [3], [15], inflammatory state [16], [17], or other unknown factors. A limitation of this report is the lack of additional neurocognitive metrics. However, because this data was collected out of interest, no additional measures were included. Further research should explore the use of wearable sensors in a larger sample while collecting neurocognitive data.
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