We have all probably had a bad night’s sleep at least once in our lives. This has undoubtedly had an impact on our next days, whether by causing us to be in a bad mood, feeling tired or having difficulty concentrating. There are many reasons for people to have a poor sleep, especially when they have been living with persistent pain. Sleeping well is crucial to our health and functioning. This is why researchers are interested in better understanding the mechanisms behind sleep and pain and therefore in finding ways to improve people’s well-being.
Goal
Although many people report in qualitative studies (i.e. studies describing a phenomenon, often through an interview) that they have sleep issues due to their pain, little is known about the mechanisms behind sleep and pain. Marc O Martel and Gilles Lavigne’s research team wanted to explore the relationship between poor sleep and pain regulation in the body by analyzing the results of several previously published studies on this topic.
Methodology
Researchers conducted a meta-analysis combining the results of 37 studies studying sleep and internal modulation (regulation) of pain, to summarize data and provide an overall picture of current knowledge. In these studies, sleep disturbances were broadly defined, including poor quality, short duration, and insomnia. Studies that measured how our body modulates pain included tests:
• Temporal summation of pain: feeling more pain when different painful stimuli occur
• Spatial summation of pain: feeling more pain when a rapid and repeated painful stimulus occurs
• Conditioned pain modulation: evaluating the level of pain in an initial test by undergoing a second painful test at the same time, which reduces the pain felt in the first test; in other words, treating pain with pain.
• Offset analgesia: disproportionate pain reduction following a small reduction in the painful stimulus
The focus was to understand if sleep disturbances disturb the functioning of internal pain modulation, considering sex differences.
Results
The results yielded mixed findings. Although from a qualitative (descriptive) standpoint, there is a link between poor sleep quality and the internal mechanisms for pain reduction, quantitative (measurable) analysis has not led to the conclusion that there is a statistically significant link between sleep and pain. In addition, sex differences emerged, showing that women had more difficulty than men to inhibit their pain after a lacking sleep.
Take home message
Further studies are required to better understand the potential relationship between sleep and pain, while also considering how this relationship changes based on individual factors such as age, sex, and race. In other words, are there particular social groups more or less likely to be affected by sleep disturbances in the context of pain?
