A large nationwide study of nearly 16,000 older adults found that symptoms suggesting REM sleep behavior disorder were surprisingly common on an online questionnaire. But most people who initially screened positive were not confirmed as probable cases when researchers followed up with a more detailed interview.
REM sleep behavior disorder can cause people to physically act out dreams. A 2026 study found that many older adults screened positive for possible RBD, but most initial positive screens were not confirmed after further assessment.
The distinction matters because REM sleep behavior disorder, or RBD, has a well-established association with Parkinson’s disease, dementia with Lewy bodies, and other neurological disorders involving the protein alpha-synuclein.
The new study does not show that thousands of participants had Parkinson’s disease or were destined to develop it. Instead, it demonstrates both the potential value and the limitations of screening large populations for a sleep disorder that can sometimes appear years before neurological disease.
Key Takeaways
- Researchers screened 15,915 adults aged 55 to 75 in Luxembourg for probable REM sleep behavior disorder.
- 12.4% initially screened positive using an online questionnaire.
- After follow-up telephone assessment, only 34.8% of the initial positive screens were confirmed as probable RBD.
- The researchers projected a prevalence of approximately 4.3% for telephone-assessed probable RBD, but these were still not definitive sleep-laboratory diagnoses.
- Confirmed isolated RBD is strongly associated with later Parkinson’s disease, dementia with Lewy bodies, and related disorders, but those long-term risk estimates cannot be applied directly to people who simply screen positive.
- The study shows why screening, probable RBD, and clinically confirmed RBD should not be treated as equivalent.
What Is REM Sleep Behavior Disorder?
During normal rapid eye movement, or REM, sleep, most skeletal muscles become temporarily inactive. This normal muscle paralysis helps prevent people from physically acting out their dreams.
In RBD, that normal suppression of muscle activity is disrupted. People may talk, shout, kick, punch, grab, or make other movements associated with their dreams. In some cases, the movements can be forceful enough to injure the sleeper or a bed partner.
RBD has attracted particular scientific interest because isolated RBD can occur before recognizable symptoms of certain neurodegenerative diseases.
Those include Parkinson’s disease, dementia with Lewy bodies, and multiple system atrophy, which are associated with abnormal accumulation of alpha-synuclein.
That makes accurately identifying RBD potentially valuable for research into the earliest stages of these diseases. It also makes inaccurate screening potentially alarming for people who interpret a positive questionnaire as evidence that they are developing Parkinson’s.
Researchers Screened Nearly 16,000 Older Adults
In the new study, Aguayo et al. (2026) analyzed data from the Luxembourg National Sleep Survey. The research was published in Scientific Reports.
Residents of Luxembourg aged 55 to 75 were invited to complete an online survey that included the 13-item RBD Screening Questionnaire.
The analysis included 15,915 participants, 54% of whom were men. Their median age was 62.
The researchers classified participants scoring seven or higher on the questionnaire as having screen-positive probable RBD.
That first stage produced a striking result: 12.4% of participants screened positive.
But the researchers did not treat those questionnaire results as diagnoses.
People with positive results were invited to complete a follow-up telephone interview. Those whose symptoms remained consistent with RBD after the interview were classified as having telephone-assessed probable RBD.
Only 34.8% of the initial positive screens were confirmed at this second stage.
Based on those results, the researchers projected that approximately 4.3% of the surveyed population had telephone-assessed probable RBD.
Most Positive Online Screens Were Not Confirmed
The drop from 12.4% at initial screening to a projected 4.3% after telephone assessment is one of the most important findings.
It suggests that a large number of people can meet the cutoff on an online RBD questionnaire without their symptoms being confirmed as probable RBD after more detailed assessment.
Other sleep behaviors and disorders can resemble aspects of RBD. Questionnaire interpretation can also introduce error.
The researchers found that questionnaire language was associated with the likelihood of screening positive. Portuguese-language respondents had higher odds of both screen-positive and telephone-assessed probable RBD.
The investigators suggested that differences in e-health literacy or questionnaire interpretation could potentially contribute to the findings. The study does not establish that language itself causes different rates of RBD.
The broader lesson is more important: an online questionnaire is a screening tool, not a diagnostic test.
Even the 4.3% Estimate Does Not Mean One in 23 Older Adults Has Confirmed RBD
The second stage improved confidence that participants had symptoms consistent with RBD, but it still did not provide a definitive sleep-laboratory diagnosis.
This distinction becomes clearer when the new findings are compared with previous research.
Cicero et al. (2021) conducted a systematic review and meta-analysis of 19 population-based studies examining the prevalence of idiopathic RBD.
The researchers found that prevalence estimates varied considerably depending on how the disorder was identified. Among five studies using a defined RBD diagnosis, the pooled prevalence was approximately 0.68%.
That is substantially lower than the 4.3% estimate of telephone-assessed probable RBD in the Luxembourg study.
The difference does not necessarily mean either estimate is wrong. The studies were measuring populations using different levels of diagnostic certainty.
That was also one of the main conclusions of the earlier meta-analysis: estimates of RBD prevalence are strongly influenced by the diagnostic methods and screening strategies researchers use.
The new Luxembourg findings reinforce that point on a particularly large scale.
Why RBD Is Connected to Parkinson’s Disease
The reason these distinctions matter so much is the strong long-term neurological risk found among people with confirmed isolated RBD.
One of the largest studies examining this relationship was conducted by Postuma et al. (2019).
Researchers combined data from 1,280 people with polysomnography-confirmed isolated RBD at 24 centers participating in the International RBD Study Group.
Participants were prospectively followed for an average of 4.6 years, with some followed for as long as 19 years.
The researchers found an overall conversion rate from isolated RBD to an overt neurodegenerative syndrome of approximately 6.3% per year.
The estimated proportion developing a defined neurodegenerative syndrome reached 73.5% after 12 years.
Those findings are one reason isolated RBD is considered an important prodromal marker for alpha-synuclein-related neurological disease.
But there is a critical difference between that study and the new Luxembourg research.
The Postuma study involved people with polysomnography-confirmed isolated RBD. The new study began with an online questionnaire and then used telephone interviews to identify probable cases.
The neurological risk found in clinically confirmed RBD populations therefore cannot simply be applied to the 4.3% of Luxembourg participants classified as probable RBD, much less to everyone who initially screened positive online.
The New Study Shows a Diagnostic Ladder
Taken together, the studies reveal a useful way to understand RBD evidence.
At the broadest level is an online questionnaire designed to identify people whose symptoms might be compatible with the disorder.
A follow-up interview can eliminate many apparent cases.
Clinical assessment can then determine whether other conditions or medications might better explain the symptoms.
For a definitive diagnosis of RBD, overnight video polysomnography is generally required to demonstrate REM sleep without the normal muscle atonia alongside the appropriate clinical history.
That hierarchy matters because each step identifies a more specific group.
The Luxembourg study showed just how large the difference can be between the first two steps. Nearly two-thirds of the people who initially screened positive were not confirmed as probable RBD during the telephone assessment.
This does not make the questionnaire useless. Screening tools are supposed to identify people who may warrant closer evaluation.
The problem arises when a positive screening result is interpreted as though it were a diagnosis.
Male Sex and Cognitive Impairment Were Associated With Probable RBD
The researchers also examined which characteristics were associated with telephone-assessed probable RBD.
Male sex and self-reported cognitive impairment were among the factors associated with probable RBD.
The cognitive finding is notable because cognitive changes can occur in neurodegenerative disorders associated with RBD.
However, the new study cannot establish that RBD caused cognitive impairment or that participants reporting cognitive problems were developing Parkinson’s disease or dementia.
The researchers were examining associations within a population survey, not tracking neurological disease progression.
The study also found geographic variation in probable RBD across Luxembourg. The authors suggested that these patterns could help guide future research into possible environmental or regional influences, but the study does not establish an environmental cause.
This Study Did Not Measure Who Developed Parkinson’s
This is perhaps the most important limitation for readers.
The Luxembourg study was not a prospective Parkinson’s disease study.
Researchers did not follow the 15,915 participants for years to determine how many eventually developed Parkinson’s disease, dementia with Lewy bodies, or multiple system atrophy.
Instead, the investigators wanted to identify people in the general population with RBD-like symptoms who could potentially undergo more detailed testing for prodromal markers in future research.
The authors described this population as a candidate group for further assessment, rather than a validated population known to be at elevated risk for an alpha-synuclein disorder.
The study therefore cannot provide an individual Parkinson’s risk estimate based on a positive RBD questionnaire.
How Does the New Study Compare With Previous Research?
Previous research already established two important findings.
First, Cicero et al. (2021) showed that estimates of how common RBD is depend heavily on how researchers define and diagnose it.
Second, Postuma et al. (2019) demonstrated that people with clinically confirmed isolated RBD can face a substantial long-term risk of developing parkinsonism or dementia.
The new research fills a different part of the picture.
Aguayo et al. (2026) show what happens when RBD screening is taken into a very large general population through an online questionnaire: many people screen positive, but most of those initial results do not remain probable cases after additional assessment.
That makes the new study important for future efforts to find people who may be in the earliest stages of neurodegenerative disease.
Large-scale online screening could potentially help researchers identify candidates for more precise testing. But without confirmation, it could also produce large numbers of false-positive or nonspecific results.
The new evidence therefore supports screening as a first step, not as a substitute for diagnosis.
What Should Someone Do If They Act Out Their Dreams?
Occasional talking or movement during sleep does not automatically mean someone has RBD.
Repeated episodes involving kicking, punching, shouting, grabbing, falling from bed, or apparently acting out vivid dreams deserve more attention, particularly when they begin later in adulthood or create a risk of injury.
Several conditions can produce unusual movements or behaviors during sleep, and medications can also affect sleep behavior.
A healthcare professional or sleep specialist can review the symptoms, medications, other sleep conditions, and neurological history and determine whether further evaluation is appropriate.
A positive online questionnaire alone cannot establish either RBD or Parkinson’s disease.
What the Evidence Actually Shows
The Luxembourg study does not show that thousands of apparently healthy older adults unknowingly have Parkinson’s disease.
It shows something more nuanced.
Among nearly 16,000 adults aged 55 to 75, 12.4% initially screened positive for probable RBD, but only 34.8% of those positive screens were confirmed after telephone assessment. The researchers projected a prevalence of approximately 4.3% for telephone-assessed probable RBD.
Even that 4.3% should not be interpreted as the prevalence of definitively diagnosed RBD.
Previous research involving confirmed isolated RBD explains why finding genuine cases matters. The disorder can precede Parkinson’s disease, dementia with Lewy bodies, and related neurodegenerative conditions.
But the new study simultaneously demonstrates why screening results, probable RBD, and confirmed RBD should not be treated as the same thing.
For researchers trying to identify people who might benefit from closer neurological monitoring or participation in future prevention trials, that distinction may be just as important as the prevalence estimate itself.
Funding and Disclosures
The study was supported by the National Centre of Excellence in Research on Parkinson’s Disease, funded by the Luxembourg National Research Fund, and by the Luxembourg Institute of Health.
The researchers stated that the funders had no role in study design, data collection and analysis, publication decisions, or preparation of the manuscript.
Several investigators reported research funding or professional relationships, which are detailed in the published study.
References
Aguayo, G. A., Rosales Jubal, E., Van Cutsem, G., Schritz, A., Tsurkalenko, O., Marques, T. M., McIntyre, D., Gomes, C. P. C., Rawal, R., Ghosh, S., Roomp, K., Pauly, C., Perquin, M., Pavelka, L., Satagopam, V., Vaillant, M., & Krüger, R. (2026). Screening Luxembourg’s older general population for probable REM sleep behaviour disorder with a nationwide online survey. Scientific Reports. https://doi.org/10.1038/s41598-026-67511-z
Cicero, C. E., Giuliano, L., Luna, J., Zappia, M., Preux, P.-M., & Nicoletti, A. (2021). Prevalence of idiopathic REM behavior disorder: A systematic review and meta-analysis. Sleep, 44(6), zsaa294. https://doi.org/10.1093/sleep/zsaa294
Postuma, R. B., Iranzo, A., Hu, M., Högl, B., Boeve, B. F., Manni, R., Oertel, W. H., Arnulf, I., Ferini-Strambi, L., Puligheddu, M., Antelmi, E., Cochen De Cock, V., Arnaldi, D., Mollenhauer, B., Videnovic, A., Sonka, K.-Y., Jung, K.-Y., Kunz, D., Dauvilliers, Y., Provini, F., . . . Pelletier, A. (2019). Risk and predictors of dementia and parkinsonism in idiopathic REM sleep behaviour disorder: A multicentre study. Brain, 142(3), 744–759. https://doi.org/10.1093/brain/awz030
