Rapid eye movement (REM) sleep behaviour disorder (RBD) is a parasomnia characterised by
the presence of acting-out behaviours in sleep and vivid dreams, which diagnosis requires
the demonstration of loss of REM atonia or an RBD episode on a video-polysomnography
(v-PSG). Importantly, patients with the isolated form of RBD are at a high risk to
develop Parkinson's disease or related neurodegenerative conditions, such as dementia
with Lewy bodies or multiple system atrophy (synucleinopathies). Hence, RBD is a
condition frequently associated to, and often preceding, a manifest neurodegenerative
disorder. It is therefore extremely relevant to identify factors that may be linked to
these early neuropathological processes. This will be key for a timely diagnosis of
isolated RBD, especially when neuroprotective trials become available.
There is also solid evidence showing that repeated concussions lead to an increased risk
to develop a neurodegenerative disorder such as Parkinson's disease, chronic traumatic
encephalopathy, all-causes of dementia, and amyotrophic lateral sclerosis.
In epidemiological studies, self-reported head injury was more frequently present in RBD
vs controls. Head injury was also proposed as a possible risk factor for probable RBD in
large community-based studies, although the diagnosis of RBD was not confirmed by v-PSG
in these cases. Of note, a higher frequency of professional football players was
demonstrated on a recent study including a large cohort of RBD patients when compared to
a control group. Moreover, in a group of deceased contact sport athletes with
neuropathology diagnosing traumatic chronic encephalopathy, probable RBD was present in
over 30% of the sample.
We hypothesise that the presence of a history of concussions or exposure to contact
sports is more frequently reported by patients with v-PSG-confirmed RBD than by sex- and
age-matched controls. There is, however, a lack of further characterisation of the
head-impact events and circumstances in which they have occurred. It would be relevant to
know whether repeated head impacts while playing contact sports or concussions that may
have not been formally diagnosed, and that may have happened in non-professional as well
as in professional sport activities, may be linked with RBD. The demonstration of a
higher percentage of concussions or exposure to contact sports in RBD would provide
greater evidence related to neuropathological changes in the context of certain sport
practices.
Given the prognostic implications of a diagnosis of RBD and the established links between
head injury and neurodegenerative conditions, it seems relevant to assess the
characteristics of previous concussions or exposure to head-impact sports in patients
with v-PSG-confirmed RBD. This will provide further evidence to help increase the
awareness of RBD (hopefully leading to a more timely diagnosis of this condition), and
potentially aid the development of health and government policies, including those
relating to safer sport practices.
As one of the major sleep disorders centres in the UK, and one of the few with expertise
in sleep neurological conditions such as RBD, it is our responsibility to assess and
report our experience on this matter.
The primary objective of this study is to assess the frequency of self-reported history
of concussions or exposure to contact sports in patients with v-PSG-confirmed RBD against
a control group (without a diagnosis of RBD).
Secondary objectives of this study will include investigating concussions/head impact
characteristics in RBD vs control group. We will also aim to search differences in
demographic and clinical variables between RBD patients with and without history of
concussions/head impact.