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Enuretic children have a higher variability in REM sleep when comparing their sleep parameters with nonenuretic control children using a wearable sleep tracker at home

  • Ellen Collier 1,
  • Carolina Varon 2,
  • Sabine Van Huffel 2,
  • Guy Bogaert 1
1 Department of Urology, UZ Leuven, Katholieke Universiteit Leuven, Leuven, Belgium 2 Department of Electrical Engineering ESAT, STADIUS Stadius Centre for Dynamical Systems, Signal Processing and Data Analytics, Katholieke Universiteit Leuven, Leuven, Belgium

Publication: Neurourol Urodyn, November 2019


That children with nocturnal enuresis (“bedwetting”) are deep sleepers is a fact that their parents often state when asking for advice. However, until today no clear difference in sleep has been observed between children who do and do not wet the bed. This study investigates the difference in sleep parameters and heart rate variability (HRV) between enuretic and control children in their home setting by using a wearable sleep tracker during a long observation period.


Twenty‐one enuretic and 18 control children, aged 6 to 12 years old, slept with a wearable sleep tracker device, a Fitbit Charge 2, for 14 consecutive days. In addition, nocturnal urine production (voided volumes and/or weight of the diaper) were measured. The HRV was calculated using the standard time and frequency domain parameters. The Kruskal‐Wallis test was applied to evaluate the differences in the sleep and HRV parameters between both groups.


Compared with healthy controls, enuretic children showed a higher standard deviation (P = .0209) of minutes spent in rapid eye movement (REM) sleep among the different nights. In addition, they showed the tendencies to fewer awakenings (P = .1161), although this was not significant. Analyzing the wet nights of the enuretic children, they showed higher autonomic activity, lower sleep efficiency and a higher restlessness compared with their dry nights and to the control group.


This 2‐weeks sleep‐study, using a wrist‐worn sleep tracker device Fitbit Charge 2, in the normal home environment has shown that enuretic children have a larger variation in their REM sleep and sleepless efficiently during a wet night when compared with non‐bedwetting children.

Commented by Prof. Konstantinos Kamperis

When asked, parents of children suffering from bedwetting would invariably say that their children are deep sleepers, difficult to awake. Furthermore, a prerequisite of an enuresis episode to occur is that children fail to awake to the signals of a full bladder. Hence the hypothesis that children with enuresis differ in terms of sleep characteristics from their continent peers.

But evaluation of sleep in children is a demanding task. Polysomnography is the golden standard but this method is time and resource consuming and thus reserved for children with apparent sleep pathology. However, with the development of new wearable tracking devices many aspects of sleep in children can now be evaluated in a cheap non-invasive fashion.

Such a devise was used buy this Belgian research group who recruited 21 monosymptomatic nocturnal enuresis patients and 18 healthy controls. Using the Fitbit Charge 2 (Fitbit corp. USA) the group collected data over a period of 14 days and nights for each child. Apart from Heart Rate Variability analysis several sleep parameters such as sleep time efficiency, light sleep and REM sleep time were evaluated. Values were tested between groups but more importantly also between wet and dry nights.

The authors find differences in time spent in REM sleep between groups, with enuresis children exhibiting almost 10% more REM time. Interestingly when evaluating wet nights several sleep parameters differed compared to both dry nights and controls. Hence, on wet nights children exhibit lower sleep efficiency, higher restless count and restless duration possibly reflecting more disturbed sleep. When evaluating heart rate variability both the standard deviation of NN interval and low frequency power (LF) were different between dry and wet nights suggesting higher autonomic activity during nights with enuresis episodes.

This study is important for several reasons. Firstly, it is one of the very few studies assessing sleep in children with enuresis in their own environment using wearable noninvasive devices. Furthermore, the study provides ample indications that sleep and autonomic function differs between wet nights and dry nights. Sleep seems less efficient with higher restless time and with higher autonomic activity during those enuresis nights. The authors speculate that this disturbed sleep architecture may lead to reduced arousal as well as cognitive dysfunction at daytime. One can also speculate whether disturbed sleep can also lead to excess urine production at night.

These hypotheses need further elucidation.

Interpreting the results of this study one has to bear in mind the general limitations of wearable devices in assessing sleep compared to conventional polysomnography. Nevertheless, the study draws attention to the sleep characteristics in enuresis children offering ideas for further research.