Insufficient sleep or poor sleep quality can reduce people’s insulin sensitivity and thus potentially increase their risk of developing type 2 diabetes.
A good night’s sleep means a lot more than being revitalised in the morning.
According to a new study, not sleeping well or insufficient sleep influences the body’s insulin sensitivity, which can increase the risk of developing type 2 diabetes.
Researchers collected data from numerous previous studies and found that insufficient sleep, lack of deep sleep and sleeping at the wrong times of the day all reduce insulin sensitivity.
According to a researcher behind the study, the importance of getting a good night’s sleep should be given higher priority.
“Many people sleep too little. This can have many physical health effects, and we can now show that it reduces insulin sensitivity. This prevents the body from channelling as much glucose from the blood to the tissues, and thus increases blood glucose, with the accompanying increased risk of developing type 2 diabetes,” explains Nina Sondrup, who conducted the research in connection with her master thesis at the University of Copenhagen and Steno Diabetes Center Copenhagen.
Nina Sondrup’s research, published in Sleep Medicine Reviews, was supervised by Anne Raben (Professor) and Jonas Salling Quist (Postdoctoral Fellow).
Systematic review of 35 previous studies
Nina Sondrup and colleagues systematically reviewed the available literature in this field, collecting data from 35 published randomised controlled trials.
These trials investigated how different types of disturbed sleep affect insulin sensitivity and the secretion of various hormones.
In the systematic review, the researchers categorised poor sleep quality based on how sleep was disturbed.
The sleep could be insufficient or interrupted, lack deep sleep or rapid eye movement (REM) sleep or be at different times of the day, such as people who work at night.
The participants’ sleep was manipulated including exposing them to noise at night so that they could not fall into deep sleep.
Short sleep duration was defined as less than the recommended 7–9 hours per night.
The different types of disturbed sleep were linked with the participants’ insulin sensitivity, measured in various ways.
“Various observational studies and animal experiments have shown that poor sleep quality can reduce insulin sensitivity and increase the risk of developing type 2 diabetes. In this study, we wanted to determine what types of poor sleep quality might cause this increased risk,” says Nina Sondrup.
Disturbed sleep reduces insulin sensitivity
The review shows that only certain types of disturbed sleep are associated with reduced insulin sensitivity: less than 6 hours of sleep, sleeping during the day instead of at night and lack of deep sleep.
In contrast, the researchers found that disturbed REM sleep or interrupted sleep, in which the participants were awakened every 90 minutes and then allowed to fall asleep again, did not affect insulin sensitivity.
The observed deterioration in insulin sensitivity may affect health.
“We are not certain that this is clinically relevant. Other studies need to examine this. But we have at least found that poor sleep quality worsened the insulin sensitivity. In addition, this occurred among healthy individuals, so future studies should investigate how poor sleep quality affects insulin sensitivity among people with prediabetes or type 2 diabetes,” explains Nina Sondrup.
The researchers also found that poor sleep quality was associated with increased secretion of cortisol, a stress hormone. This indicates that poor sleep quality and/or short sleep duration stress the body, and animal experiments have also shown that this reduces insulin sensitivity
Greater focus on sleep
Nina Sondrup thinks that the results indicate the need for increasing the focus on improving sleep in Denmark.
In some countries, such as United States, the official public health recommendations include sleep, whereas other countries, including Denmark, have not implemented sleep in the recommendations.
Nina Sondrup is convinced that greater focus on sleep can help to prevent the development of various lifestyle-related diseases.
“The problem is that many people who are busy do not give priority to sleep, but this is unhealthy. Our study indicates that sleep is very important for proper insulin sensitivity, and focusing on good sleep quality could also potentially prevent the development of type 2 diabetes,” concludes Nina Sondrup.