Who, what & why?

Stress is a common cause of periods of insomnia, and whilst some people seem remarkably resilient, others are obsessive worriers whose sleep quality really suffers. Psychology and health researchers from Concordia University in Montreal, Canada designed an intelligent study to try and understand the relationship between daytime heart rate variability (HRV), HRV response to periods of worry and sleep disturbance.

What did they do?

Exam stressThey evaluated changes in sleep disturbances in response to a natural stressor among a population of 22 university students comprising both good sleepers and individuals with insomnia symptoms.

The researchers took advantage of the fact that students are normally low stress individuals, but stress levels rise substantially in the week before final examinations. This meant they could examine changes in sleeping patterns as a result of realistic life stresses.

For the HRV response to stress test, they used the early part of the semester to provide a baseline HRV level. After this had been taken, they were asked to identify the topic they tend to worry the most often and most intensely about, and to worry about this topic for the next 3 minutes, during which time their HRV was measured again.

The students were asked to fill in detailed sleep quality and insomnia questionnaires for the low stress and high stress period prior to the final exams.

What did they find?

They found that although HRV during the low stress period was weakly associated with sleep quality at that time, it was much more strongly associated with the self rated sleep quality score (PSQI) during the high stress period in the build up to exams.

Unsurprisingly, the students HRV fell significantly during the worry test, and the HRV during this test was strongly associated with sleep quality scores during both low and high stress periods. In other words, low HRV during the worry test predicted increases in sleep disturbances during periods of higher daytime stress.

What does it mean?

In short, the researchers concluded that they discovered a new vulnerability measure. By examining the amount of HRV reduction from baseline during a standardized worry inducement test, future sleep quality problems during natural stress periods could be predicted.

These kinds of tests are enlightening for psychologists or human resource managers trying to predict who is going to be able to handle stressful jobs and situations better than others, but for the rest of us, can we do better than just saying ‘don’t worry’ or ‘don’t lose sleep over this?’.

Practical implications

The insight that baseline HRV, as well as the dip during an artificial worry exercise, can predict sleep quality during stressful periods means that we can improve our level of resilience. By using tools like the ithlete HRV app together with lifestyle measures such as the ithlete subjective scales we can learn more about ourselves, and therefore build a higher sustained baseline HRV level, resulting in improved all round health and fitness. During periods of stress we can also experiment with techniques such as Pranayama breathing and cold showers that have been reported by many to boost their parasympathetic HRV both acutely when stress is present and for considerable periods of time after each session.



The original research can be found here:

High-frequency heart rate variability during worry predicts stress-related increases in sleep disturbances.