"We found that sleep-disordered breathing was common when chronic pain patients took prescribed opioids," explains lead author Lynn R. Webster, MD, from Lifetree Clinical Research and Pain Clinic in Salt Lake City, Utah. "We also found a direct dose-response relationship between central sleep apnea and methadone and benzodiazepines, an association which had not been previously reported."
Opioids, effective medications for chronic pain treatment, are often used for cancer patients, but are now gaining widespread acceptance as long-term therapy for chronic pain unrelated to cancer. An increasing number of patients with nonmalignant chronic pain are receiving around-the-clock pain relief through opioid therapy.
The researchers studied sleep lab data on 140 patients taking around-the-clock opioid therapy for chronic pain to assess the potential and prevalence sleep apnea in opioid treated pain patients. All patients were on opioid therapy for at least six months with stable dosing for at least four weeks.
The investigators say that their results show a higher than expected prevalence of sleep disordered breathing in opioid treated chronic pain patients. Obstructive and central sleep apnea syndromes occurred in the studied population at a far greater rate (75%) than is observed in the general population, where obstructive sleep apnea is known to be underdiagnosed but has been estimated at roughly 2% to 4%. Central sleep apnea is estimated at 5% in people older than 65 years and from 1.5% to 5% in men less than 65 years old.
People who stop breathing during sleep because of faulty brain control have central sleep apnea as opposed to obstructive apnea, which is triggered by obesity and other health problems and accompanied by loud snoring.
The investigators comment that the absence of crescendo-decrescendo breath size commonly associated with central sleep apnea suggests that the central sleep apnea mechanism is different for people taking opioids than the general public. They suggest it could be related to the direct effects of opioids on the part of the brain that controls respiration.
The authors also note that if opioid medications increase sleep apnea risk as their research suggests, then chronic pain patients who are prescribed opioids have a higher risk of morbidity and mortality. "The challenge is to monitor and adjust medications for maximum safety, not to eliminate them at the expense of pain management," Dr. Webster concludes.
"The recent flurry of news reports of deaths associated with methadone use, and the synergy of opioids and benzodiazepines in causing respiratory depression, highlight the importance of Dr. Webster's research.
Clearly we need more studies of these mechanisms as well as ways of identifying those at risk. Doctors and patients who are considering opioid medication for pain control, must balance this risk against the potential for improved quality of life," comments Rollin M. Gallagher, MD, Editor-in-Chief of Pain Medicine.