A Single

1Department of Neurology, McGill University, Montreal General Hospital, Montreal, Québec, Canada

2Centre d'Études Avancées en Médecine du Sommeil, Hôpital du Sacré-Cœur de Montréal, Montréal, Québec, Canada

3Unité des pathologies du sommeil, Hôpital Pitié-Salpétriére, APHP and Inserm U975-CRICM-Pierre and Marie Curie University, Paris, France

4Department of Neurology, Innsbruck Medical University, Innsbruck, Austria

5Neurology Service, Hospital Clinic de Barcelona, IDIBAPS, CIBERNED, Barcelona, Spain

6Department of Neurology Dokkyo Medical University Koshigaya Hospital, Saitama, Japan

7Department of Neurology, Hôpital Gui de Chauliac, Montpellier, INSERM U1061, Montpellier, France

8Department of Neurology, Philipps-Universität, Marburg, Germany

9Washington University Multidisciplinary Sleep Center, St. Louis, Missouri, USA

10Sleep Center, Department of Cardiovascular and Neurological Sciences, University of Cagliari, Italy

11Danish Center for Sleep Medicine, University of Copenhagen, Denmark

1Department of Neurology, McGill University, Montreal General Hospital, Montreal, Québec, Canada

13Research Institute of the McGill University Health Center, Montreal, Québec, Canada

12Department of Epidemiology and Biostatistics and Occupational Health, McGill University, Montreal, Québec, Canada

13Research Institute of the McGill University Health Center, Montreal, Québec, Canada

3Unité des pathologies du sommeil, Hôpital Pitié-Salpétriére, APHP and Inserm U975-CRICM-Pierre and Marie Curie University, Paris, France

4Department of Neurology, Innsbruck Medical University, Innsbruck, Austria

14Department of Neurology Dokkyo Medical University School of Medicine, Tochigi, Japan

7Department of Neurology, Hôpital Gui de Chauliac, Montpellier, INSERM U1061, Montpellier, France

8Department of Neurology, Philipps-Universität, Marburg, Germany

8Department of Neurology, Philipps-Universität, Marburg, Germany

10Sleep Center, Department of Cardiovascular and Neurological Sciences, University of Cagliari, Italy

15Sleep Disorders Center, Universitá Vita-Salute San Raffaele, Milan, Italy

2Centre d'Études Avancées en Médecine du Sommeil, Hôpital du Sacré-Cœur de Montréal, Montréal, Québec, Canada

16Department of Psychiatry, Université de Montreal, Montreal, Québec, Canada

Idiopathic REM sleep behavior disorder (RBD) is a parasomnia that is an important risk factor for PD and Lewy body dementia. Its prevalence is unknown. One barrier to determining prevalence is that current screening tools are too long for large-scale epidemiologic surveys. Therefore, we designed the REM Sleep Behavior Disorder Single-Question Screen (RBD1Q), a screening question for dream enactment with a simple yes/no response.

Four hundred and eighty-four sleep-clinic– based participants (242 idiopathic RBD patients and 242 controls) completed the screen during a multicenter case-control study. All participants underwent a polysomnogram to define gold-standard diagnosis according to standard criteria.

We found a sensitivity of 93.8% and a specificity of 87.2%. Sensitivity and specificity were similar in healthy volunteers, compared to controls or patients, with other sleep diagnoses.

A single-question screen for RBD may reliably detect disease, with psychometric properties favorably comparable to those reported for longer questionnaires.

REM sleep behavior disorder (RBD) is a parasomnia characterized by dream-enactment behavior, diagnosed by clinical history in combination with video-polysomnography to document REM atonia loss. Idiopathic RBD (iRBD) is receiving increased attention as an important risk factor for neurodegenerative diseases, especially alpha-synucleinopathies.2–4

Despite increasing recognition of its importance, knowledge of RBD epidemiology is limited. Except for two studies, which primarily screened for sleep injury (a subtype of RBD)5,6 no large-scale epidemiologic surveys have estimated RBD prevalence. A major barrier to conducting prevalence studies is that RBD is probably uncommon, thus requiring very large epidemiologic surveys. Such large surveys are generally broad, assessing many nonsleep outcomes, with strict limitations upon the time demands upon respondents. This precludes the use of polysomnographic diagnosis and lengthy screening questionnaires. Therefore, simple (i.e., one- or two-question) screens are needed to assess RBD in large-scale epidemiologic surveys. To meet this need, we designed the RBD Single-Question Screen (RBD1Q) a single “yes-no” question that queries the classic dream-enactment behavior of RBD. We present here the validation results of this question, in relation to gold-standard polysomnographic diagnosis, in a 12-center case-control study.

Participants were selected from 12 centers of the International REM Sleep Behavior Disorder Study Group and were recruited from 2008 to 2011. All RBD patients had RBD diagnosis confirmed by polysomnography according to the International Classification of Sleep Disorders-27; namely, loss of REM atonia on polysomnographic trace in association with history of dream-enactment or witnessed dream enactment during REM sleep on video polysomnogram. Patients were not blinded to RBD diagnosis when they completed the questionnaire. Convenience sampling was used (i.e., maximal recruitment each center). All cases had neurological examination confirming the absence of dementia (defined as Mini-Mental State Examination [MMSE] Table 1Sensitivity and Specificity of the RBD1Q ScreenRBDControlTotalRBD screen +22631257 PPV = 87.9%RBD screen −15211226 NPV = 93.4%241242Sensitivity = 93.8%Specificity = 87.2%Open in a separate window

Abbreviation: NPV, negative predictive value.

In subgroup analysis, specificity in healthy volunteers (85.4%; 95% CI = 72.8, 92.8) was similar to sleep center controls (87.6%; 95% CI = 82.2, 91.5). Although obstructive sleep apnea can mimic RBD,10 specificity was not lower in obstructive sleep apnea patients (92.2%; 95% CI = 84.8, 96.2). Exclusion of patients who lived alone did not improve either sensitivity (93.5%) or specificity (87.6%). Exclusion of participants taking antidepressants (n = 52; 42 with RBD) did not appreciably alter results (sensitivity = 93.8%; specificity = 90.4%). Ninety-seven patients were taking clonazepam, 30 melatonin, and 15 both medications. After patients on either symptomatic therapy were excluded, results were similar (sensitivity = 92.2%; specificity = 87.7%).

We found that the RBD1Q could detect RBD with 94% sensitivity and 87% specificity in a well-characterized, clinic-based cohort of RBD patents and controls.

The RBD1Q compares favorably to other questionnaire-based diagnostic tools. The first questionnaire tool developed for RBD was the 13-item Stiasny-Kolster RBD-Screening Questionnaire (RBDSQ), which was evaluated in 54 patients with RBD in different conditions (19 with iRBD, 33 with narcolepsy, and 2 with PD), 133 healthy subjects, and 160 sleep-center controls. The questionnaire demonstrated 96% sensitivity, but only 56% specificity, when using sleep-center patients as controls. Specificity was 92% when healthy subjects were used as controls; however, specificity cannot be reliably assessed for these subjects, because they did not undergo polysomnography (both clinical interview and the screening questionnaire could miss RBD). A Japanese version of this questionnaire was assessed in 52 iRBD patients, 55 controls with obstructive sleep apnea on successful continuous positive airway pressure therapy, and 62 age-matched healthy subjects (again without polysomnography confirmation in healthy subjects).12 Sensitivity was 88.5% and specificity was 90.9% in apnea patients (and 96.9% in healthy subjects). The Japanese version was also tested in 45 PD patients—at a one-point higher cut-off, sensitivity was 84% and specificity was 96%13. The recently designed RBD-HK (Hong Kong) scale includes 13 questions, with two frequency assessments for each question (lifetime and 1-year frequency).14 Using predominantly sleep-center controls, sensitivity was estimated at 82%, with 87% specificity.

Both the RBDSQ and RBD-HK involve 13 questions and therefore may not be practical in large/broad epidemiologic surveys in which sleep is one of many components assessed. Yet, the essence of RBD can be described relatively simply, suggesting that multiple questions may be unnecessary. The Mayo Sleep questionnaire contains a single question of dream enactment targeted to caregivers. Although independently designed, it is very similar to our question (“Have you ever seen the patient appear to ‘act out his/her dreams’ while sleeping? [punched or failed arms in the air, shouted or screamed]).15 There are five follow-up questions in the case of a positive response. In dementia patients, the questionnaire given to their caregivers detected RBD with 98% sensitivity and 74% specificity. It has not been tested in iRBD. Therefore, there appears to be good potential for single-question RBD screens administered either to caregivers or to patients themselves, depending on circumstances.

Some limitations should be noted. Just as with validation studies for the RBDSQ and RBD-HK, our screen was tested in patients who were followed in sleep centers for RBD. Patients were therefore presumably aware of their RBD status. By virtue of having sought out medical attention, they are also likely to be more severely affected and may be knowledgeable about their condition—therefore, they may more readily recognize their symptoms on screens. Therefore, sensitivity and specificity may be different in population-based studies. Unfortunately, this limitation may be unavoidable—even assuming a poor screen sensitivity (67%), with an iRBD prevalence of 2%, 1,500 general population screen negatives would have to undergo polysomnography to detect 10 screen-negative/disease-positive individuals—therefore, reliable estimates of sensitivity in general population RBD cases may never be available. Also, in uncommon conditions, positive predictive value (PPV) can be low, even in the face of excellent specificity (e.g., with 2% prevalence, a test with 90% specificity and 100% sensitivity results in a PPV of only 16.7%). Therefore, direct estimate of PPV in a general population study would be of considerable utility. Note because of concerns about specificity, the RBD1Q does not screen for sleep talking or sleep yelling—there are a subset of patients for whom this is the only manifestation, and these may be missed by the screen. Our high sensitivity (93.8%) suggests that this is a relatively minor limitation, at least for clinic-based RBD samples. Also, this study did not include patients with non-REM parasomnias (one control with non-REM parasomnia was excluded)—clearly, these patients may respond positively to the screen, further reducing specificity. Finally, although our study size is large, sensitivity and specificity estimates in smaller subgroups have wide confidence intervals.

In summary, the RBD1Q demonstrated good sensitivity and specificity in diagnosing RBD. This result supports its future potential for the assessment of RBD prevalence in broad-scale epidemiologic surveys of disease.

Funding agencies: This work was supported by Canadian Institute of Health Research, Fonds de la recherche en santé du Québec.

Relevant conflicts of interest/financial disclosures: Nothing to report. Full financial disclosures and author roles may be found in the online version of this article.