Sleep apnoea is a sleep-related breathing disorder that can have immense health consequences. Not only do those affected suffer from severe daytime fatigue due to lack of sleep, but their life expectancy is also limited by cardiovascular problems and high blood pressure. In most cases, sleep apnoea syndrome is treated with a respirator, which also has a generally positive effect. However, many patients find these masks annoying and therefore do not use them as prescribed. So far, there are no drugs for obstructive sleep apnoea. However, one study shows that dronabinol could be an alternative or adjunctive treatment.
What is sleep apnoea?
Obstructive sleep apnoea syndrome (OSAS) is a nocturnal breathing disorder that affects the upper airways. By relaxing the muscles in the mouth and throat, the brain’s command to take a breath cannot be carried out. The constricted space in the throat leads to the typical snoring. There are also pauses in breathing, which can last from 10 seconds to a few minutes and occur several times an hour.
Symptoms of obstructive sleep apnoea:
- loud and irregular snoring with breathing interruptions
- heavy daytime sleepiness
- reduced performance (microsleep)
- morning headaches
- nightly awakening from sleep
- possible depression, anxiety, potency and libido disorders
Sleep apnoea syndrome occurs mainly in men over 40 years of age. A high BMI is also a risk factor. Most patients with sleep apnoea are obese, i.e. very overweight. The figures on how many people in Germany suffer from sleep apnoea sometimes fluctuate considerably. One reason for this is that the disease is usually not diagnosed in the first place: According to estimates, this is true for 80 to 90 percent of cases. However, experts assume that 4 to 9 percent of the population is affected. 
Doctors distinguish between obstructive sleep apnoea syndrome and central sleep apnoea syndrome. The first form is by far the more common: 90 percent of patients suffer from OSAS. Central sleep apnoea syndrome, on the other hand, which affects less than ten percent of sleep apnoea sufferers, is characterised by the absence of impairment (obstruction) of the upper airways.
Sleep apnoea: health effects and treatment options
Untreated sleep apnoea is a great burden for those affected.  Because of the interrupted night’s sleep, patients lack the deep sleep phases. The body is unable to recover sufficiently, so that those affected suffer from daytime tiredness, which in turn leads to concentration problems and performance deficits. The risk of accidents is increased by the possibility of microsleep.
The long-term health risks of obstructive sleep apnoea syndrome are enormous. They include high blood pressure and cardiovascular diseases, diabetes, stroke and depression. In summary, the disease thus leads to an earlier death.   
To prevent this from happening, it is important that patients first reduce risk factors. In the case of OSAS this usually means consistent weight reduction. Patients should also avoid nicotine and alcohol. The treatment of existing underlying diseases and the adjustment of blood pressure are essential.
In addition, the use of a ventilator (CPAP) can reduce the risk of mortality to the level of a healthy person. It reduces daytime sleepiness, lowers blood pressure and reduces the number of hospital admissions. However, the use of the ventilator is only successful if patients use it as prescribed and treatment is monitored by regular sleep checks.
Unfortunately, the respirator is difficult for many people to tolerate. They therefore wear it only irregularly or only for a few hours during the night. The rate of people not continuing with this therapy is high. As there is no medication available for sleep apnoea, there is a great need for alternative treatment. 
Dronabinol – a therapy for sleep apnoea?
The synthetic cannabis active substance dronabinol achieved interesting results in a phase II study in the treatment of obstructive sleep apnoea syndrome. The double-blind study of the University of Illinois in Chicago and North-western University was placebo-controlled and conducted at different centres. According to the researchers, this 2018 study shows
“that dronabinol is safe and well tolerated in participants with moderate-to-severe OSA.”
As there are only a few treatment options for sleep apnoea, this study is very interesting. The researchers explain: “There remains an important and unmet need for fully effective and acceptable treatments in obstructive sleep apnoea (OSA). At present, there are no approved drug treatments.” 
The study was conducted in 73 adults with moderate or severe obstructive sleep apnoea. They were randomly given either a placebo, 2.5 mg dronabinol or 10 mg dronabinol daily. They took the cannabis drug one hour before bedtime for up to 6 weeks. Dronabinol had a better outcome in the higher dose in the trial. Participants who received 10 mg of dronabinol a day expressed the highest overall satisfaction with the treatment.
“Dronabinol dose-dependently reduced AHI and improved self-reported but not objective sleepiness (…)”.  The researchers therefore believe that taking THC can be a useful alternative treatment or adjunct therapy for sleep apnoea.
The researchers are convinced that larger clinical trials are needed to find the best possible approach to cannabinoid treatment for OSAS.
Innovative approach to cannabinoid therapy
Drug treatment of sleep apnoea is a new approach because it targets the brain rather than the physical problem of the airways. This is what Prof. Phyllis Zee, a researcher involved in the study, told Sleep Review magazine. This reflects the belief that sleep apnoea is not just a physical problem, but can be caused by several factors. One of them is poor regulation of the upper airway muscles by the brain, Zee said.
“The CPAP device targets the physical problem but not the cause,” Zee says. “The drug targets the brain and nerves that regulate the upper airway muscles. It alters the neurotransmitters from the brain that communicate with the muscles. Better understanding of this will help us develop more effective and personalized treatments for sleep apnoea.“
Cannabinoids: a new treatment for sleep apnoea?
Although respirators are very effective in the treatment of obstructive sleep apnoea, many patients cannot cope with them. Drug treatment for this condition would therefore be of enormous benefit to those affected.
Research has shown positive results with THC (dronabinol) in sleep apnoea. Breathing interruptions were reduced and subjective general health and daytime tiredness improved. This approach is innovative because it does not just treat the physical problem, but targets the cause of the breathing stops.
However, the scientists consider “it is unlikely that any drug treatment could be fully effective in all people with OSA.”  Other large trials could help us understand which people benefit from cannabinoid treatment and what the best treatment for obstructive sleep apnoea might be for each individual. Zausig, Y., Arzt, M. Perioperative Versorgung von Patienten mit obstruktiver Schlafapnoe. Pneumologe 11, 386–393 (2014). https://doi.org/10.1007/s10405-014-0791-y  Young T, Palta M, Dempsey J, Peppard PE, Nieto FJ, Hla KM. Burden of sleep apnea: rationale, design, and major findings of the Wisconsin Sleep Cohort study. WMJ. 2009;108(5):246-249.  Hale CS. Obstructive sleep apnea and cardiovascular disease and mortality: the argument for causality. J Insur Med. 2005;37(4):272-282.  Parish JM, Adam T, Facchiano L. Relationship of metabolic syndrome and obstructive sleep apnea. J Clin Sleep Med. 2007;3(5):467-472.  Carley DW, Prasad B, Reid KJ, et al. Pharmacotherapy of Apnea by Cannabimimetic Enhancement, the PACE Clinical Trial: Effects of Dronabinol in Obstructive Sleep Apnea. Sleep. 2018;41(1):zsx184. doi:10.1093/sleep/zsx184