Casting a Wider Net for the Diagnosis of RBD
Every healthcare professional walks into the examination room with predetermined biases regarding the patients they see. Fifty-year-old obese man? OSA, of course. Twenty-year-old woman with daytime sleepiness? Could be narcolepsy. A man comes to the sleep center with his wife and she has a black eye? REM behavior disorder (RBD) is suddenly on your radar.
We are all taught to start a list of differential diagnoses during patient encounters. But as we gain experience, it’s the exceptions to the rules that teach us the most: A 25-year-old professional tennis player without an ounce of fat who has severe apnea on his sleep study; a 60-year-old man who tells you he gets weak in the knees when laughing and has a 40-year history consistent with narcolepsy; a 16-year-old woman who has brief “sleep attacks” and an EEG that shows spike and wave discharges instead of REM sleep.
The take-home lesson for me has been to cast a wide net when fishing for a diagnosis and try to be very sure before crossing off diagnoses from the list. I know, I mixed the metaphor.
We can take a lesson from cardiology. For decades, the assumption was that men have heart attacks and women don’t. Successful efforts to reduce the risk of heart attacks were aimed at men and had encouraging results. But epidemiologists found that women had heart disease as well, and because they assumed they didn’t have heart disease they were less likely to seek treatment than men. Women are less likely to be part of clinical trials and are less likely to be prescribed aggressive treatment. Women have different risk factors and different symptoms than men. Heart disease remains the leading cause of death in women.1
A new study published in the journal SLEEP shatters our preconceptions about RBD.2 The typical RBD patient comes to the sleep center with a history of violent behavior associated with dream recall. In your mind, you have a picture of a middle-aged man, right? Maybe wearing a plaid jacket and proudly showing you the belt and restraints devised to prevent his frequent episodes of jumping out of bed? Thanks, Mark Mahowald and Carlos Schenck.3
Like heart disease, early estimates of the prevalence of RBD were based on symptomatology, which turns out to be different in men and women. In a large population-based study, participants were asked to complete several questionnaires. Two specific questions were used to screen patients: “Have you ever lashed about, hitting or kicking?” and “Have you ever actually done what you dreamt, e.g., gesticulating or lashing about?” Participants who answered yes to either of these questions moved on to the next phase of the study.
The incidence of RBD was determined in these participants with symptoms using analysis of muscle activity during a sleep study. Increased muscle tone during REM sleep — known as REM without atonia — was determined by computer analysis and sleep specialist review. The diagnosis of RBD was defined as a combination of symptoms and REM without atonia.
Surprisingly, there was no gender difference in the incidence of RBD in this study. Or, maybe not so surprisingly. Here’s my admittedly biased and single-subject take on the issue.
Most patients presenting to the sleep center for evaluation of symptoms related to RBD are accompanied by a bed partner with a complaint of dream enactment. As a bed partner, I confess that I am pretty much unaware of what happens during the night. My wife could re-enact a dream of marching with her high school band singing “We are the Champions” at the top of her voice and I would probably sleep right through it (although I am looking forward to the Queen biopic coming out soon). On the other hand, any movement or vocalization on my part is reported in detail the following morning and sometimes immediately after it happens.
It’s possible that women have different symptoms of RBD. But in the Haba-Rubio study, they started with participants who endorsed the questions in the survey that were associated with dream enactment.2 Then they found REM without atonia, an early indicator of RBD.
There’s another piece to this story that makes the diagnosis of RBD potentially very important. We have known for years that there is an association between RBD and degenerative neurological diseases such as Parkinson’s disease. There can be several decades between the diagnosis of RBD and the onset of neurodegenerative diseases. This window allows for the possibility of neuroprotective treatments which, admittedly, have not yet been developed.
Nevertheless, casting the wide net and keeping an open mind to the possibility of RBD in women is something that sleep professionals should strive to attain. After all, not all RBD patients wear plaid jackets. For more information, check out our new Journal Club module on REM Behavior Disorder. (You must be a member to access.)
- Maas, A. H. E. M., & Appelman, Y. E. A. (2010). Gender differences in coronary heart disease. Netherlands Heart Journal, 18(12), 598–602.
- Haba-Rubio J, et al. (2017). Prevalence and determinants of REM sleep behavior disorder in the general population. Sleep, 41(2) doi: 10.1093/sleep/zsx197.
- Schenck CH, Bundlie SR, Ettinger MG, Mahowald MW (1986). Chronic behavioral disorders of human REM sleep: A new category of parasomnia. Sleep, 9(2) 293–308, doi: 10.1093/sleep/9.2.293.