In what researchers describe as the first study to evaluate the prevalence of short onset rapid eye movement period (SOREMP) latency, an unexpected finding was revealed.
A retrospective analysis of a repository of almost 80,000 general sleep clinic patient studies revealed that SOREMP occurrences are very rare and are highly indicative of the possibility that a patient has narcolepsy.
“What was most surprising to us is that [short onset rapid eye movement latency], it’s so rare that we didn’t really have a number in mind,” says Alyssa Cairns, PhD, a research scientist for SleepMed Inc, and co-author of the study published in Sleep in 2015, in an interview with Sleep Review. “It only occurred in 0.7% of the people we sampled; now that’s a really small number of people.”
For several years, SleepMed had been aggregating de-identified data of polysomnography and multiple sleep latency test (MSLT) test results. By examining the immense amount of data collected, the study authors were able to identify the prevalence of a very rare phenomenon among general sleep clinic patients as well as an isolated group of patients that appeared to be at high risk for narcolepsy.
Because this REM sleep abnormality occurs in a very specific subgroup of people, Cairns says she and the co-author of the study, Richard Bogan, MD, sought to figure out how many people actually walked into sleep labs with this abnormal characteristic found in those with narcolepsy.
“Essentially what we found even in the group of people at high risk of narcolepsy, short onset rapid movement latency was rare,” says Cairns. “This study quantified the base rate of this very abnormal finding.”
So what’s the takeaway for those who suspect narcolepsy in patients? What’s next?
The study helps sleep study practitioners better understand what to do when they suspect that a person has narcolepsy.
It’s encouraged that a MSLT is performed unless there is something else that suggests otherwise that the excessive sleepiness the patient is experiencing is not due to narcolepsy, according to Cairns.
The something else could be shift work, habitual restrictions of sleep, PAP titration issues, and other causes that sleep clinicians know to cause narcolepsy-like symptoms.
“The study goes on to reinforce our understanding of how the brain works under normal circumstances,” Cairns says. “After a MSLT if you see the occurrence of a short onset rapid eye movement latency, you can save off the patient from the consequences of what untreated narcolepsy can bring.”