Researchers from the University of Texas Health Science Centre at San Antonio (UT Health San Antonio) School of Dentistry have created a first-of-its-kind sleep apnoea model for studying chronic pain.

The study, published in July 2024 in Science Signaling, explained the mechanism behind persistent pain related to obstructive sleep apnoea.

More than 100m people worldwide are affected by obstructive sleep apnoea, with four million sufferers in the UK, according to the Sleep Apnoea Trust.

The condition causes a person to stop breathing numerous times while sleeping.

Reduced sleep time and sleep quality can lead to numerous health problems, including chronic pain, which is diagnosed more in people with obstructive sleep apnoea than those with normal sleep patterns.

Nathaniel Jeske, primary investigator and director of research for the department of oral and maxillofacial surgery at the School of Dentistry at UT Health San Antonio, said, “We are looking at maladaptive neuroplasticity in these primary nociceptors that are representing persistent pain, which serves as a bridge between the acute and the chronic.”

The peripheral nervous system controls messages from nerves that run throughout arms, legs and skin and sends these messages to the central nervous system. Nociceptors in this system are nerve cells specialised in detecting stimuli that produce pain.

Peter Loomer, dean of the UT Health San Antonio School of Dentistry, said, “This study represents a significant advancement in our understanding of the relationship between sleep apnoea and chronic pain.

“Insight into the role of oxygen deprivation in pain sensitisation will pave the way for innovative treatment approaches that could enhance patient outcomes.”

To mimic the effects of obstructive sleep apnoea in a mouse model, the researchers created a chronic intermittent hypoxia environment. After 14 days, the team observed an increase in cytokines, which are molecules released by the immune system that tell other cells to produce an inflammatory state.

In a state of chronic reduced oxygen, these released cytokines cause sensitivity in nociceptors that produce prolonged sensitivity to pain.

Ken Hargreaves, director of the Center for Pain Therapeutics and Addiction Research and professor in the department of endodontics at the university’s School of Dentistry, said, “The puzzle of pain remains unsolved and has led to many untoward events, including accelerating the epidemic of opioid use disorder.

“The findings of Nathaniel and his research team offer a novel and potentially insightful approach for resolving this puzzle for patients with obstructive sleep apnoea.”

Results from the study have suggested that a treatment that corrects the chronic lack of oxygen or targets the peripheral macrophages could correct persistent pain for some obstructive sleep apnoea patients.

Future research can explore these and other targeted treatments by identifying the mechanisms behind pain related to the condition.

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