Marie Dumont

Université de Montréal | UdeM · Department of Psychiatry

Background Individuals complaining of a delayed sleep schedule are expected to have shorter sleep duration and lower sleep quality when they must comply with morning obligations. The changes in the sleep schedule imposed by morning obligations may in turn decrease the stability and amplitude of their rest-activity cycle. These expectations were onl...

Study objectives: Sleep-wake disturbances are frequent among patients hospitalized for traumatic injuries but remain poorly documented because of the lack of tools validated for hospitalized patients. This study aimed to validate actigraphy for nighttime sleep monitoring of hospitalized patients with severe traumatic injuries, using ambulatory pol...

Recent evidence points toward an association between higher non‐visual sensitivity to light and a later circadian phase in young adults complaining of a delayed sleep schedule. Light exposure in the evening may therefore induce a larger suppression of melatonin production in these individuals, which might: (a) bias home estimates of melatonin onset...

Study Objectives To test whether the sleep-wake cycle disruption in patients hospitalized with traumatic brain injury (TBI) (1) is also found in patients with traumatic injuries other than TBI (non-TBI) and (2) is associated with a weaker or abnormal circadian clock signal. Methods Forty-two non-mechanically ventilated and non-sedated patients hos...

Abstract The discovery of intrinsically photosensitive retinal ganglion cells (ipRGCs) marked a major shift in our understanding of how light information is processed by the mammalian brain. These ipRGCs influence multiple functions not directly related to image formation such as circadian resetting and entrainment, pupil constriction, enhancement...

Beyond its essential visual role, light, and particularly blue light, has numerous non-visual effects, including stimulating cognitive functions and alertness. Non-visual effects of light may decrease with aging and contribute to cognitive and sleepiness complaints in aging. However, both the brain and the eye profoundly change in aging. Whether th...

Introduction: Most adults with moderate to severe traumatic brain injury (TBI) report persistent sleep-wake disturbances. Whether these complaints are either associated with abnormal sleep-wake patterns or can be explained by TBI-related characteristics is unclear. The present study aimed at characterising the subjective and objective sleep-wake p...

The discovery of intrinsically photosensitive retinal ganglion cells (ipRGCs) marked a major shift in our understanding of how light is processed by the mammalian brain. These ipRGCs influence multiple functions not directly related to vision such as the synchronization of circadian rhythmicity, pupil constriction, the regulation of alertness and s...

A number of factors can contribute to a delayed sleep schedule. An important factor could be a daily profile of light exposure favoring a later circadian phase. This study aimed to compare light exposure between 14 young adults complaining of a delayed sleep schedule and 14 matched controls and to identify possible associations between habitual lig...

Introduction Sleep-wake disturbances (SWD) are among the most prevalent and disabling consequences reported after a moderate-to-severe traumatic brain injury (TBI), but remain poorly understood. Our aim was to better characterize post-TBI SWD using a combination of subjective and objective measures. Moreover, we aimed to verify whether specific typ...

Introduction Sleep-wake disturbances (SWD) are present in the acute phase of moderate-severe traumatic brain injury (TBI), and could be related to circadian disturbances caused by the brain injury. The goal of this study was to 1) compare the rest-activity and melatonin rhythms of moderate-severe TBI patients to that of patients with severe orthope...

Introduction Light, particularly blue light, increases alertness, performance and cognitive brain responses, but age-related decrease in the effects of light has been reported. The extent to which these age-related modifications are caused by changes at the level of the eye (because of senile miosis and lens yellowing) or the brain is unclear. Met...

Introduction We recently demonstrated that the sleep-wake cycle is severely altered in the acute stage of moderate to severe traumatic brain injuries (TBI). In general, these patients have short sleep and wake bouts dispersed over the 24 h. This study aimed to explore whether early markers of TBI severity predict acute sleep-wake cycle disturbances...

Objective: To assess factors that might contribute to a delayed sleep schedule in young adults with sub-clinical features of delayed sleep phase disorder. Methods: Two groups of 14 young adults (eight women) were compared: one group complaining of a delayed sleep schedule and a control group with an earlier bedtime and no complaint. For one week...

Objective: To investigate whether the progressive recuperation of consciousness was associated with the reconsolidation of sleep and wake states in hospitalized patients with acute traumatic brain injury (TBI). Methods: This study comprised 30 hospitalized patients (age 29.1 ± 13.5 years) in the acute phase of moderate or severe TBI. Testing sta...

Background: Sleep-wake disturbances are frequently reported following traumatic brain injury (TBI), but they remain poorly documented in the acute stage of injury. Little is known about their origin and evolution. Case presentation: This study presents the case of a patient in the acute phase of a severe TBI. The patient was injured at work when...

https://www.anses.fr/fr/system/files/AP2011SA0088Ra.pdf

Notwithstanding its effects on the classical visual system allowing image formation, light acts upon several non-image-forming (NIF) functions including body temperature, hormonal secretions, sleep-wake cycle, alertness, and cognitive performance. Studies have shown that NIF functions are maximally sensitive to blue wavelengths (460–480 nm), in com...

Purpose: The aim of this study was to investigate the association between depressive symptoms severity and amplitude of diurnal variations in depression symptoms in patients with chronic obstructive pulmonary disease (COPD). Design: Prospective, observational proof-of-concept study. Methods: Fourteen participants with moderate/severe COPD comp...

Background and objectives: The onset of pervasive sleep-wake disturbances associated with traumatic brain injury (TBI) is poorly understood. This study aimed to (a) determine the feasibility of using polysomnography in patients in the acute, hospitalized stage of severe TBI and (b) explore sleep quality and sleep architecture during this stage of...

L’occurrence d’un traumatisme craniocérébral (TCC) est un problème de santé publique majeure. Les troubles du sommeil et de l’éveil sont parmi les symptômes les plus persistants et les plus déshabilitants à la suite d’un TCC. Or, les études empiriques portant sur l’apparition de ces symptômes, leur chronicisation et leur traitement demeurent non co...

Decreased melatonin production, due to nighttime exposure to light, has been proposed as one of the physiological mechanisms increasing cancer risk in night workers. However, few studies measured melatonin production in night workers, and most of these studies did not measure melatonin over 24 h. One study compared total melatonin production betwee...

Light exposure, particularly blue light, is being recognized as a potent mean to stimulate alertness and cognition in young individuals. Aging is associated with changes in alertness regulation and cognition. Whether the effect of light on cognitive brain function changes with aging is unknown, however. Cross-sectional study. Functional Neuroimagin...

Abstract Aging is associated with important modifications in the sleep–wake cycle even among healthy individuals. These changes may be related to many factors including changes in the circadian regulation of the sleep–wake cycle (e.g., phase advance, reduced amplitude, vulnerability of the sleep–wake cycle to circadian challenges), in circadian ent...

Sleep-wake disturbances are among the most persistent sequelae after traumatic brain injury (TBI) and probably arise during the hospital stay following TBI. These disturbances are characterized by difficulties sleeping at night and staying awake during the day. The aim of the present study was to document rest-activity cycle consolidation in acute...

Introduction Based on clinical observations, sleep–wake cycle disturbances, arise in the days following traumatic brain injury (TBI), and remain among the most persistent and debilitating symptoms. The aim of this study was to document the evolution of rest-activity cycle consolidation in the acute phase of moderate/severe TBI, and its association...

Abstract The purpose of this pilot study was to determine the impact of time of day on the acute response to incremental exercise in chronic obstructive pulmonary disease (COPD). Fourteen subjects (nine men) aged 71 ± 7 years with moderate to severe airflow obstruction (FEV1: 58 ± 13% predicted) followed a counterbalanced randomized design, perform...

Light regulates multiple non-image-forming (or nonvisual) circadian, neuroendocrine, and neurobehavioral functions, via outputs from intrinsically photosensitive retinal ganglion cells (ipRGCs). Exposure to light directly enhances alertness and performance, so light is an important regulator of wakefulness and cognition. The roles of rods, cones, a...

Many nonvisual functions are regulated by light through a photoreceptive system involving melanopsin-expressing retinal ganglion cells that are maximally sensitive to blue light. Several studies have suggested that the ability of light to modulate circadian entrainment and to induce acute effects on melatonin secretion, subjective alertness, and ge...

Decreased melatonin production, due to acute suppression of pineal melatonin secretion by light exposure during night work, has been suggested to underlie higher cancer risks associated with prolonged experience of night work. However, the association between light exposure and melatonin production has never been measured in the field. In this stud...

In most situations, complete circadian adjustment is not recommended for night workers. With complete adjustment, workers experience circadian misalignment when returning on a day-active schedule, causing repeated circadian phase shifts and internal desynchrony. For this reason, partial circadian realignment was proposed as a good compromise to sta...

SW density and characteristics per sleep cycle in chronotypes. SW density, amplitude, slope (left panels), frequency, negative and positive phases duration (right panels) are shown per sleep cycle for M-types (open diamonds) and E-types (black squares) for the firsts 4 sleep cycles of baseline and recovery nights. SW properties were compared using...

Vulnerability to the reduction in natural light associated with fall/winter is generally accepted as the main trigger of seasonal affective disorder (SAD), whereas light therapy is a treatment of choice of the disorder. However, the relationship between exposure to light and mood regulation remains unclear. As compared with green light, blue light...

Brain recovery after prolonged wakefulness is characterized by increased density, amplitude and slope of slow waves (SW, <4 Hz) during non-rapid eye movement (NREM) sleep. These SW comprise a negative phase, during which cortical neurons are mostly silent, and a positive phase, in which most neurons fire intensively. Previous work showed, using EEG...

A close temporal relationship was shown between the onset of melatonin secretion at night and the worsening of restless legs syndrome (RLS) symptoms, suggesting that melatonin may play a role in the genesis of this phenomenon. To test this hypothesis we studied the effects of the administration of exogenous melatonin and, conversely, the suppressio...

Circadian misalignment between the endogenous circadian signal and the imposed rest-activity cycle is one of the main sources of sleep and health troubles in night shift workers. Timed bright light exposure during night work can reduce circadian misalignment in night workers, but this approach is limited by difficulties in incorporating bright ligh...

To assess as whether insomniacs have higher nighttime blood pressure (BP) and a blunted day-to-night BP reduction, recognized markers of increased risk of cardiovascular morbidity and mortality. Prospective case-control study. University hospital-based sleep research laboratory. Thirteen normotensive subjects with chronic primary insomnia (9 women,...

It has been reported that the sensitivity to light of the circadian system of animals and human subjects can be modulated following long-term exposure to a given light environment. Animal studies have also shown that long-term exposure to a light regimen, or light history, will have a significant impact on the retinal structure and function, the ob...

Vigilance levels of 12 morning types (M-types) and 12 evening types (E-types) were investigated after a baseline night, 2 nights of sleep fragmentation (5 min of forced awakening every half-hour) and a recovery night. Sleep timing was adjusted to the preferred sleep schedule of each subject. Daytime vigilance levels were assessed with test series i...

In addition to being necessary for vision, light also plays a primary role in circadian physiology. Humans are diurnal animals and their biological clock synchronizes their physiological functions in such a way that functions associated with activity happen in the daytime while functions associated with rest occur at night. A misalignment between t...

To evaluate the influence of chronotype on sleep stages and quantitative sleep EEG when sleep pressure is increased and sleep schedule remains constant. A 5-day session comprising an adaptation night, a baseline night, two nights of sleep fragmentation, and a recovery night. Chronobiology laboratory. Twenty-four healthy subjects aged 19-34 years: 1...

Caffeine is often used to counteract sleepiness generated by sleep deprivation, jet lag, and shift-work, and is consumed at different times of day. Caffeine also has effects on sleep. However, little is known about the interaction between sleep deprivation, circadian timing, and caffeine consumption on sleep. In this study, we compared the effects...

Morning-type individuals (M-types) have earlier sleep schedules than do evening types (E-types) and therefore differ in their exposure to the external light-dark cycle. M-types and E-types usually differ in their endogenous circadian phase as well, but whether this is the cause or the consequence of the difference in light exposure remains controve...

The aim of the present study was to evaluate the influence of season of birth and photoperiod at birth on diurnal preference in young adults. Participants were 1591 volunteers aged 17-35 years (69% women). The scores obtained on the Morningness-Eveningness Questionnaire (MEQ) of Horne and Ostberg were first assessed as a function of gender and seas...

Morningness-eveningness has been associated with the entrained circadian phase. However, we recently identified morning and evening types having similar circadian phases. In this paper, we compared parameters of slow-wave activity (SWA) decay in non-rapid-eye-movement (NREM) sleep between these two subgroups to test the hypothesis that differences...

Circadian types classify individuals according to their preferred timing for activity and sleep, morning and evening types showing, respectively, early or late preferences. This characteristic has been associated with corresponding differences in circadian sleep propensity. In this study, quantitative analysis of the sleep EEG in antero-posterior d...

The mechanisms underlying age-related changes in the signal from the biological clock have yet to be determined. The authors sought to determine if the phase advance of circadian melatonin rhythm during the middle years of life is related to different patterns of habitual light exposure. Forty-one healthy subjects between the ages of 22 and 58 y we...

In response to progressively brighter flashes, the amplitude of the photopic b-wave of the human electroretinogram (ERG) first increases, then saturates at a maximal value (V(max)) to finally decrease with the brightest flashes. The purpose of this study was to investigate if this "photopic hill" could be modulated with the use of stimuli of differ...

To evaluate the influence of chronotype (morning types and evening types) on sleep stages and quantitative sleep electroencephalograms when constraints on the sleep schedule are minimal and when sex difference is taken into account. A 48-hour session in the laboratory, including 2 nights of polysomnography, preceded by 7 days of ambulatory actigrap...

It is now well established that symptoms of restless legs syndrome (RLS) are worsened by immobility and that their severity fluctuates according to a circadian pattern with a maximum occurring in the late evening or during the night. However, no study has ever attempted to dissociate these two effects. The objective of this study was to evaluate th...

A shorter phase angle between habitual wake time and underlying circadian rhythms has been reported in evening types (E types) compared to morning-types (M types). In this study, phase angles were compared between 12 E types and 12 M types to verify if this difference was observed when the sleep schedule was relatively free from external social con...

Recently, it was suggested that the intensity of restless legs syndrome (RLS) symptoms may be modulated by a circadian factor. The objective of this study was to evaluate, during a 28-hour modified constant routine, the nycthemeral or circadian variations in subjective leg discomfort and periodic leg movements (PLMs) and to parallel these changes w...

Fourteen healthy subjects (8 women, 6 men, aged 22-35 yr) were recruited. Each subject was exposed, in a counterbalanced order, to bright white light (BWL: 3000 lux) and to dim red light (DRL: <15 lux) at a 1-week interval. Light treatments were administered from 00:30 to 04:30 h during sleep deprivation. Salivary melatonin and urinary cortisol con...

Objectives: 735 kV powerlines increase residential exposure to electric and magnetic fields (EMF) for people living nearby. Some studies have suspected effect of EMF on depressive symptoms and there is plausibility for such an effect via the melatonin pathway. Recently, we found that aged and overweight women living near high power lines had lower...

With progressively brighter stimuli, the amplitude of the photopic b-wave first increases, briefly saturates and then decreases gradually to reach a plateau, where the amplitude of the b-wave equals that of the a-wave; a phenomenon previously presented as the photopic hill. The unique presentation of this luminance-response function seriously compl...

Purpose: With progressively brighter flashes, the amplitude of the photopic b-wave first increases, briefly saturates and then diminishes gradually; a phenomenon previously presented as the Photopic Hill. We present reproducible key descriptors of this function. Methods: Full field photopic ERGs were recorded from normal subjects to flashes of whit...

Evaluate the diurnal variation of retinal function, as measured with the electroretinogram (ERG), in subjects with an early (morning type: M-type) or a late (evening type: E-type) circadian phase. Subjects (n = 24) were recruited according to their scores on a Morningness-Eveningness Questionnaire assessing preferences in, e.g., bedtime, waketime,...

An anomaly in the retinal adaptation processes to the decreased light exposure in winter has been suggested as a contributing factor in winter depression. The purpose of this study was to investigate seasonal variations in rod sensitivity in normal subjects and in subjects with seasonal mood variations. Nine normal subjects (5 men, 4 women, aged 21...

The present study examined the similarities between the diurnal time courses in the waking EEG activity and the psychomotor performance. The aim was to verify if some ongoing changes in the excitability of the cortical nerve cells across the daytime could facilitate the sensorimotor processing. EEG recordings and performance results for the Four Ch...

Light exposure was measured in 30 permanent night nurses to determine if specific light/dark profiles could be associated with a better circadian adaptation. Circadian adaptation was defined as a significant shift in the timing of the episode of melatonin secretion into the daytime. Light exposure was continuously recorded with ambulatory wrist mon...

In 1998, the authors studied the effect of residential exposure to electric and magnetic fields from high-power lines on female urinary excretion of 6-sulfatoxymelatonin (6-OHMS) in the Quebec city, Canada, metropolitan area. A sample of 221 women living near a 735-kV line was compared with 195 women the same age living away from any power lines. P...

Daytime measures of sleep latency and subjective alertness do not correlate with one another, suggesting that they assess different aspects of alertness. In addition, their typical diurnal variations show very different time courses. Quantitative analysis of the waking electroencephalogram (EEG) has been proposed as an objective measure of alertnes...

To test the hypothesis that nightworkers' diurnal sleep complaints are associated with the timing of melatonin secretion. After a minimum of three consecutive night shifts, the subjects were admitted to the laboratory for 24 hours during which they were allowed to eat and sleep ad lib. Urine was collected every two hours under dim illumination (<25...

Electroencephalograms (EEGs) of 14 normal subjects were recorded every 2 h during 38 h constant routines. Adjacent narrow frequency bands (NFB) with similar temporal trends were grouped into frequency clusters. Clusters I (2.00-7.75 Hz) and III (11.00-14.75 Hz) exhibited similar time courses which may reflect both the duration of time awake and a c...

There are many work schedules which affect workers’ sleep-wake cycle. In the present paper, shiftwork will refer essentially to nightwork, including both permanent nightwork and rotating night/day work. The difficulties experienced by shiftworkers are multi-facetted and vary with the type of schedule, type of work (physical and mental workload), fa...

Considering the success of bright light therapy in seasonal affective disorders, it was suggested that seasonal mood disorders are triggered by decreased exposure to bright light in the winter; however, no previous studies have used objective measures to assess seasonal patterns of bright light illumination in subjects with seasonal mood variations...

This study was designed to test the hypothesis that bright light (BL) can have a stimulating effect on vigilance even in the absence of suppression of melatonin secretion and that this effect can be detected when measured in subjects with low vigilance levels. Seven normal subjects were exposed to bright-white light (BL group) and seven to dim-red...

Little is known about the natural pattern of seasonal and diurnal illumination to which normal people are exposed, especially in northern latitudes. In this study, ambient illumination of normal volunteers living at a latitude of 45 degrees 31' N was recorded with ambulatory photosensors worn for 5 to 6 days in winter and summer. Results from 12 no...

This study explored the relationship between past night-shift work and present quality of sleep, first by a survey and second with standard laboratory recordings. Nurses (n = 479) working on a day or evening schedule answered a questionnaire about past night-shift work and present quality of sleep. An insomnia index, derived from the questionnaire,...

Moderate circadian phase shifts were induced by 3 days of bright light exposure, without changing the habitual sleep schedule. Daytime sleep propensity was evaluated with multiple sleep latency tests (MSLT) conducted before and after the light treatment. Phase shifts were estimated using the core body temperature rhythm recorded during constant rou...