Original ArticleSleep following sport-related concussions
Introduction
A growing literature reports short- and long-term sleep and vigilance problems in patients who sustained traumatic brain injury (TBI) [1], [2], [3], [4], [5], [6], [7], [8]. In fact, it has been shown that 30 to 80% of patients with TBI complain of insomnia, longer sleep onset latency, difficulty to maintain sleep, fatigue, and daytime sleepiness. Moreover, these symptoms were found to be among the most common and most severe complaints after a TBI [9], [10]. Possible focal or diffuse lesions to the brainstem structures may explain sleep disturbances and fatigue after a TBI; however, the exact mechanisms involved in the etiology of these problems are still unknown. Surprisingly, more sleep problems are reported in patients with mild TBI than in patients with moderate or severe TBI [1], [4], [8].
In spite of the high incidence of sleep and vigilance problems following TBI, only a few studies have used objective measures to describe sleep and wake disturbances in these patients and even fewer have done it with patients with mild TBI, even if mild TBI represents as many as 70 to 90% of all TBIs [11]. Kaufmann and coworkers [12] studied the sleep characteristics of teenagers who had complaints about their sleep quality three years after a mild TBI. Their major finding was that teenagers with mild TBI showed poorer sleep efficiency than control subjects as measured with polysomnography and actigraphy. In another study carried out on eight teenagers who sustained a mild TBI, Parsons and coworkers [13] observed no anomaly in polysomnographic parameters at three times of recordings (72 h, 6 weeks and 12 weeks post-trauma). However, significant power reduction of low EEG frequency activities (0.5–9.75 Hz) during non-rapid eye movement (NREM) sleep was observed as the delay since the TBI increased. In a more recent study done by Schreiber and colleagues [14], mild TBI patients with chronic sleep complaints were evaluated in the sleep laboratory, and an increase in stage 2 NREM sleep and a decrease in REM sleep were found in these patients as well as significant daytime sleepiness in comparison with healthy control subjects.
Athletes practicing contact sports, such as hockey and football, are at high risk to sustain multiple TBIs during their career. The incidence of concussions occurring in sports and their impact on brain functions are currently a major concern. Most sport-related concussions correspond to a mild TBI with a Glasgow Coma Scale score varying from 13 to 15 [15], normal structural neuroimaging results and infrequent loss of consciousness or post-traumatic amnesia [16], [17]. While the severity of injury is generally mild, it has been shown that a history of concussion increases six times the risk of sustaining another concussion [18], which can explain that 50% of football players have a history of multiple concussions [19], [20]. The short- and long-term impacts of multiple concussions in athletes are still a matter of debate [21], [22], [23].
As for patients who sustained a mild TBI in contexts other than sports, 35 to 70% of concussed athletes report sleep problems, fatigue, and vigilance disturbances after a concussion [17], [24], [25]. No study has yet investigated the impact of sport-related concussions on sleep using standardized sleep questionnaires and polysomnography. The study of sleep and vigilance in concussed athletes is of high importance, since their performance may be altered by sleep disturbances and/or vigilance decrement.
The aim of the study was thus to subjectively and objectively measure sleep quality in concussed athletes. We used standardized sleep questionnaires, polysomnographic recording and we verified the integrity of the EEG activity during wakefulness, REM, and NREM sleep by quantitative EEG analysis (QEEG) in order to understand the nature of sleep complaints and vigilance problems in this population.
Section snippets
Subjects
Ten athletes who sustained concussions were included in this study. They all experienced a concussion during the last year (see Table 1 for detailed clinical characteristics) and they all had a self-reported history of at least two sport-related concussions, which were validated during the clinical interview. Diagnosis with regard to the last concussion was made by the team physicians according to the recently proposed criteria [26], namely the presence of one or more of the following
Subjective symptoms
Results obtained with the questionnaires are presented in Table 2. A significant group difference was observed for the Post Concussion Symptom Scale score; athletes with concussions reported more symptoms than control athletes. When each item was compared separately, significant group differences were observed for physical (dizziness, headaches, and feeling pressure in head, p < 0.01), cognitive (difficulty concentrating, p < 0.05) and neurobehavioral symptoms (difficulty falling asleep,
Discussion
The aim of the present study was to measure vigilance and sleep characteristics after concussions in athletes by using standardized questionnaires, polysomnographic recording, and QEEG. The main finding was that no difference in sleep architecture was found between concussed and control athletes; additionally, no difference was found in either NREM or REM sleep QEEG. However, concussed athletes showed significant increased delta and reduced alpha activities in the waking QEEG and reported poor
Acknowledgments
This research was supported by the Canadian Institutes of Health Research (J.M. and N.G.), by the Fonds pour la Recherche en Santé du Québec (M.L. and N.G.) and by the Natural Sciences and Engineering Research Council of Canada (V.M.). J.M. holds a Canada Research Chair in Sleep Disorders and M.L., a Canada Research Chair in Developmental Neuropsychology. The authors are grateful to Emmanuelle Baron, MD, Jimmy Gosselin, B.Sc., and Sylvie Rompré for their assistance.
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