New research shows that poor quality of sleep increases pain sensitivity. A researcher says that treatment for people with chronic pain could include ensuring high-quality sleep.
About 20% of the global population experiences chronic pain, but people experience pain differently. Some people are very sensitive to pain, and others can tolerate it better – but the underlying reasons for this are unclear.
Chronic pain also differs greatly from acute pain, since chronic pain involves various systems of the human body, including the nervous system, the immune system and the psychological factors.
A new study shows that poor quality of sleep strongly affects how the nervous system interprets pain, such that people with poor sleep quality are more sensitive to pain.
The study also shows that women with poor quality of sleep are more severely affected. This is useful information since about two thirds of the people who experience chronic pain are women.
According to a researcher behind the study, the overall treatment plan for people with chronic pain may need to include improvements in sleep quality.
“Chronic pain is complex, and we have previously shown that the immune system, the nervous system and symptoms of anxiety and depression can affect pain severity. Developing a drug that can target all these systems simultaneously is very difficult, and this can make chronic pain difficult to treat. Our studies show that poor quality of sleep negatively affects all human body systems, and we should therefore investigate whether improving sleep quality can positively affect these systems and reduce pain,” explains Kristian Kjær-Staal Petersen, PhD, dr.med., Associate Professor, Department of Health Science and Technology, Aalborg University, Denmark.
The research, which was carried out in collaboration with Elisabet Dortea Ragnvaldsdóttir Joensen, Laura Frederiksen, Signe Vindbæk Frederiksen, Emilie Stjernholm Valeur, Rocco Giordano and Emma Hertel, has been published in the European Journal of Pain.
Pain hypersensitivity increases the risk of chronic pain
The researchers aimed to learn more about pain hypersensitivity, how pain and sleep are linked and whether the sexes differ in these respects.
Hypersensitivity to pain is a risk factor for developing chronic pain after surgery and responding less well to drug treatment for pain.
“But we do not know why some people are hypersensitive to pain and what factors affect this hypersensitivity. We aimed to learn more about that with this study,” says Kristian Kjær-Staal Petersen.
Participants’ sleep disrupted to test pain tolerance
The researchers invited 59 healthy people to participate, 30 of them were women. Their pain hypersensitivity was measured using various methods, such as a pressure pain threshold in which the skin is pressed with increasing force until they experience pain.
This method enabled the researchers to measure whether three or four kilograms of pressure was required before pain was experienced, and lower numbers would indicate a higher degree of hypersensitivity to pain.
The participants had their pain hypersensitivity measured before and after three days of disrupted sleep.
The researchers disrupted sleep by waking participants up and giving them simple tasks to complete, such as photographing the contents of their refrigerator.
“This is similar to a person with, for example, osteoarthritis in one knee waking up because of the pain. With this experiment, we simulated how disrupted sleep experienced by people with chronic pain affects pain hypersensitivity,” explains Kristian Kjær-Staal Petersen.
Poor sleep increases women’s pain sensitivity more than men
The experiment showed that poor quality of sleep made individuals much more sensitive to pain.
According to Kristian Kjær-Staal Petersen, this is not a big surprise, but the study provided figures for how much sleep quality affected the sexes differently.
Kristian Kjær-Staal Petersen says that the most interesting result of the study is that poor quality of sleep affected women’s pain tolerance more strongly than men’s.
“This is useful because women comprise two thirds of the people with chronic pain. One reason may be that poor sleep more strongly affects their nervous system and thus their pain tolerance,” he notes.
Sleep might treat chronic pain and its sequelae
According to Kristian Kjær-Staal Petersen, the results are important because pain and poor quality of sleep affect billions of people globally.
The researchers have now linked pain, poor sleep and sex in a novel way.
The study also contributes to the overall picture of the links between sleep and pain and other disorders.
Kristian Kjær-Staal Petersen’s research has also shown that the people experiencing chronic pain with the worst sleep quality also often experience more severe pain and more symptoms of anxiety, depression and catastrophic thinking. Poor quality of sleep and pain are thus linked to mental health.
Finally, the researchers also previously examined links between chronic pain, poor sleep and a weakened immune system.
“Pain, inflammation, mental health and sex are clinically interconnected in a way that we did not know before, and the crucial link may be sleep. This also means that getting people with chronic pain to sleep better has very great potential. This may not only reduce their pain sensitivity but also improve their mental health and reduce inflammation. This would kill three birds with one stone without using medication,” says Kristian Kjær-Staal Petersen.
He emphasises that, although many people struggle with poor sleep and that the treatment of chronic problems can be difficult, simple tips can help.
“Chronic sleep problems may require advanced therapy, but for healthy people, going to bed and getting up at the same time every day, ensuring a comfortable temperature in the bedroom and avoiding alcohol can improve sleep quality,” concludes Kristian Kjær-Staal Petersen.
