Listening to Calming Words While Asleep Boosts Deep Sleep

Researchers at the GIGA Center of Research Cyclotron in Belgium partnered with colleagues from the University of Fribourg in Switzerland to better understand how the body’s reactions to calming words impacted sleep by analyzing heart rate data. 

The study built on previous research that established that slow-wave sleep lengthened and the quality improved when relaxing words were played during non-rapid eye movement sleep (NREM). Trusted Source Oxford Academic Journals (OUP) OUP publishes the highest quality journals and delivers this research to the widest possible audience. View Source

Slow-wave sleep, also known as deep sleep, is the third NREM sleep stage associated with slowed breathing, relaxed muscles, as well as memory and immune function. Sufficient slow-wave sleep is integral to waking up feeling refreshed. 

With the effect of calming words on the mind established, the researchers hoped to take the findings a step further. Noting that other studies found heart rate variability could be used as a way to study the sleeping brain, Trusted Source Frontiers Frontiers is one of the largest and highest-cited publishers in the world and has information on more than 600 academic disciplines. View Source they planned to analyze heart rate data collected during sleep. Their aim: determining to what extent the sleep-improving effect of relaxing words on the mind might also be connected to calming effects on the body. 

To test their hypothesis, the researchers analyzed electrocardiography (ECG) data collected during a standard lab-based sleep study. They compared the interval between heartbeats on nights when relaxing words were played during sleep to nights when neutral words were played. 

On the nights sleepers experienced the calming words, the heartbeat interval was longer, indicating a slower heart rate and a more relaxed body. 

The researchers then used data models to corroborate the interaction between cardiac and brain activity and their associated effect on slow-wave sleep. The results suggested that the body and mind effects were not independent but share an integrated relationship that resulted in the positive changes relaxing words have on slow-wave sleep.   

This connection between outside stimuli and sleep health offers new opportunities for scientists. In particular, the study authors advocate for more sleep studies that use a systemic approach to sleep, measuring impacts on both the mind and body. 

For sleepers, this whole-body perspective could lead to new therapies focused on comprehensive sleep health and pave the way for the regular use of soothing sleep-time recordings aimed at improving overall well being.