Christian Cajochen

Universitäre Psychiatrische Kliniken Basel | UPK · Centre for Chronobiology

I am delighted to introduce this collection of abstracts from our recent 35th Annual SLTBR Meeting in Prague [...]

The human sleep–wake cycle is regulated by two distinct processes: the circadian timing system (CTS) and the sleep–wake homeostatic (SWH) process. The CTS is driven by a small region in the anterior hypothalamus of the brain, which is known as the “circadian clock.” By contrast, the SWH can be conceptualized as an hourglass, whereby sleep pressure...

Circadian rhythms are inherent to living organisms from single cells to humans and operate on a genetically determined cycle of approximately 24 hours. These endogenous rhythms are aligned with the external light/dark cycle of the Earth's rotation and offer the advantage of anticipating environmental changes. Circadian rhythms act directly on human...

Light influences human physiology and behaviour by regulating circadian rhythms, melatonin secretion, and alertness. Previous research has reported sex differences in melatonin secretion and circadian rhythms, possibly related to women's greater sensitivity to bright light. Other studies have suggested reduced photosensitivity and earlier circadian...

Light exposure at night can suppress melatonin production and increase alertness, primarily through the action of melanopsin-containing intrinsically photosensitive retinal ganglion cells (ipRGCs). This study investigated whether cone photoreceptors also influence melatonin suppression and subjective alertness using non-visual metameric light emitt...

Whether light exposure during the day reduces non-visual light effects later in the evening has not been studied in adolescents. We investigate whether afternoon-early evening (AEE) light interventions (130 lx, 2500 lx, 4.5 hours, compared to 6.5 lx) would increase melatonin levels during later evening light exposure (130 lx) in a counterbalanced c...

Internal circadian phase assessment is increasingly acknowledged as a critical clinical tool for the diagnosis, monitoring, and treatment of circadian rhythm sleep−wake disorders and for investigating circadian timing in other medical disorders. The widespread use of in‐laboratory circadian phase assessments in routine practice has been limited, mo...

Exposure to short-wavelength light before bedtime is known to disrupt nocturnal melatonin secretion and can impair subsequent sleep. However, while it has been demonstrated that older adults are less affected by short-wavelength light, there is limited research exploring differences between adolescents and young adults. Furthermore, it remains uncl...

This study investigates the impact of varying light intensities throughout the day on motor activity levels in adolescent girls aged between 14-16, who are students at a boarding school. The study lasted for three weeks, with each week consisting of four days. During this period, participants experienced three different lighting conditions from 07:...

Concerns have been raised about the possibility of effects from exposure to short wavelength light (SWL), defined here as 380–550 nm, on human health. The spectral sensitivity of the human circadian timing system peaks at around 480 nm, much shorter than the peak sensitivity of daytime vision (i.e., 555 nm). Some experimental studies have demonstra...

Sleep, circadian rhythms, and mental health are reciprocally interlinked. Disruption to the quality, continuity, and timing of sleep can precipitate or exacerbate psychiatric symptoms in susceptible individuals, while treatments that target sleep—circadian disturbances can alleviate psychopathology. Conversely, psychiatric symptoms can reciprocally...

The pupil modulates the amount of light that reaches the retina. Not only luminance but also the spectral distribution defines the pupil size. Previous research has identified steady-state pupil size and melatonin attenuation to be predominantly driven by melanopsin, which is expressed by a unique subgroup of intrinsically photosensitive retinal ga...

Evening exposure to short-wavelength light can affect the circadian clock, sleep and alertness. Intrinsically photosensitive retinal ganglion cells expressing melanopsin are thought to be the primary drivers of these effects. Whether colour-sensitive cones also contribute is unclear. Here, using calibrated silent-substitution changes in light colou...

It is well known that variations in light exposure during the day affect light sensitivity in the evening. More daylight reduces sensitivity, and less daylight increases it. On average days, we spend less time outdoors in winter and receive far less light than in summer. Therefore, it could be relevant when collecting research data on the non-image...

The Society for Light Treatment and Biological Rhythms (SLTBR) held this year’s annual meeting at the Ecole Polytechnique Fédérale (EPFL) in Lausanne, Switzerland from 30 May to 1 June in conjunction with the Day Light Academy (DLA) [...]

Exposure to natural daylight benefits human well-being, alertness, circadian rhythms and sleep. Many workplaces have limited or no access to daylight. Thus, we implemented a light-panel (“Virtual Sky“), which reproduced nature-adapted light scenarios. In a laboratory office environment, three lighting scenarios were presented during the day: two li...

Evening exposure to short-wavelength light can acutely affect the circadian clock located in the suprachiasmatic nuclei, sleep, and alertness. The intrinsically photosensitive retinal ganglion cells (ipRGCs) expressing the photopigment melanopsin are thought to be the primary drivers of these effects. Much less is known about the contribution of th...

Study objectives: We aimed to examine the association between self-rated and clinician-rated sleep disturbances and C-reactive protein (CRP), an objective marker of inflammation, in pediatric depression. Methods: Two hundred fifty-six children and adolescents (15.2 ± 1.6 y, 72.3% female) with moderate to severe symptoms of depression participate...

The circadian system orchestrates sleep timing and structure and is altered with increasing age. Sleep propensity, and particularly REM sleep is under strong circadian control and has been suggested to play an important role in brain plasticity. In this exploratory study, we assessed whether surface-based brain morphometry indices are associated wi...

Evening light-emitting visual displays may disrupt sleep, suppress melatonin and increase alertness. Here, we control melanopic irradiance independent of display luminance and colour, in 72 healthy males 4 h before habitual bedtime and expose each of them to one of four luminance levels (i.e., dim light, smartphone, tablet or computer screen illumi...

This article describes the development of a device to investigate the non-visual responses to light: The Light-Dosimeter (lido). Its multidisciplinary team followed a user-centred approach throughout the project, that is, their design decisions focused on researchers’ and participants’ needs. Together with custom-made mountings and the software Lid...

To better understand the impact of environmental light on processes that underlie cognitive activity, Lasauskaite and Cajochen (2018) recently proposed a theoretical model that predicts how light's correlated color temperature (CCT) affects effort. Here we tested whether the effects of CCT of light on effort-related cardiovascular response also ext...

Acute caffeine intake has been found to increase working memory (WM)-related brain activity in healthy adults without improving behavioral performances. The impact of daily caffeine intake—a ritual shared by 80% of the population worldwide—and of its discontinuation on working memory and its neural correlates remained unknown. In this double-blind,...

Die zirkadiane Rhythmik und die Schlafhomöostase sind zwei Hauptkomponenten der Schlaf-Wach-Regulation. Das fein aufeinander abgestimmte Zusammenspiel dieser zwei oszillatorischen Prozesse erlaubt dem Menschen optimale Aufmerksamkeit während des Wachseins am Tag und konsolidierten Schlaf in der Nacht. Kleine Abweichungen im Zusammenspiel beider Pro...

Heatwaves are occurring more frequently and are known to affect particularly night-time temperatures. We review here literature on how night-time ambient temperature changes affect body temperature and sleep quality. We then discuss how these temperature effects impact particularly vulnerable populations such as older adults, children, pregnant wom...

Enhancing lighting conditions in institutions for individuals with dementia improves their sleep, circadian rhythms and well-being. Here, we report first findings that exposure to brighter light during daytime may support the immune response to the annual influenza vaccination. Eighty older institutionalized patients suffering from dementia (54 wom...

Pre-sleep exposure to short-wavelength light suppresses melatonin and decreases sleepiness with activating effects extending to sleep. This has mainly been attributed to melanopic effects, but mechanistic insights are missing. Thus, we investigated whether two light conditions only differing in the melanopic effects (123 vs. 59 lux melanopic EDI) d...

Evening exposure to electric light can acutely suppress melatonin levels and adversely affect subsequent sleep. We conducted a systematic review with meta-analysis investigating the influence of evening illuminance levels on polysomnographically (PSG)-assessed sleep. We also explored how melanopsin (expressed in melanopic equivalent daylight illumi...

Background Perinatal depression (PND) is a severe complication of pregnancy, but there are no established risk factors predicting the disease. Evening chronotype has been associated with unhealthy lifestyle habits and adverse outcomes during pregnancy. In this study, we aimed to clarify whether chronotype can predict symptoms and/or occurrence of P...

Objective: Perinatal depression (PND) is a severe complication of pregnancy, affecting both mothers and newborns. Bright light therapy (BLT) has only been tested in a few studies for treating either antenatal or postnatal depression. We conducted a pilot trial to investigate the efficacy and safety of BLT for PND occurring at any time across the p...

Study objectives Pre-sleep exposure to short-wavelength light acutely suppresses melatonin, increases vigilance, and decrease sleepiness with the activating effects extending to sleep. The effects have mainly been attributed to melanopic effects of light, but mechanistic insights are missing. Thus, we investigated whether two metameric light condit...

Caffeine has been reported to acutely increase working memory (WM)-related brain activity without a significant enhancement in performances in healthy adults. As a ritual in the society, however, the impacts of daily caffeine intake on WM-related brain activities remain unknown. This double-blind randomized crossover study aimed to investigate the...

Ocular light exposure has important influences on human health and well-being through modulation of circadian rhythms and sleep, as well as neuroendocrine and cognitive functions. Prevailing patterns of light exposure do not optimally engage these actions for many individuals, but advances in our understanding of the underpinning mechanisms and eme...

Improving indoor lighting conditions at the workplace has the potential to support proper circadian entrainment of hormonal rhythms, sleep, and well-being. We tested the effects of optimized dynamic daylight and electric lighting on circadian phase of melatonin, cortisol and skin temperatures in office workers. We equipped one office room with an a...

Growing evidence indicates an association between reduced dream recall and depressive symptomatology. Here, we tested the prediction that reduced dream recall in individuals experiencing major depressive disorder (MDD) is due to alterations in circadian and sleep processes. Nine young healthy women (20-31 years) and eight young unmedicated women (2...

Caffeine elicits widespread effects in the central nervous system and is the most frequently consumed psychostimulant worldwide. First evidence indicates that, during daily intake, the elimination of caffeine may slow down, and the primary metabolite, paraxanthine, may accumulate. The neural impact of such adaptions is virtually unexplored. In this...

Study objectives Age-related cataract decreases light transmission at the most sensitive spectrum for circadian photoentrainment, with negative ramifications for human health. Here, we assessed whether intraocular lens replacement (IOL) in older patients with previous cataract was associated with increased stability and amplitude of circadian rest-...

Light-induced melatonin suppression data from 29 peer-reviewed publications was analysed by means of a machine learning approach to establish which light exposure characteristics (i.e. photopic illuminance, five α-opic equivalent daylight illuminances (EDIs), duration and timing of the light exposure, and the dichotomous variables pharmacological p...

Research on the non-visual responses to light under real-world conditions has been hindered by the lack of suitable measuring devices. Here, we present a novel, portable and miniaturised light-dosimeter attached to a spectacle frame, taking measurements in the near-corneal plane. The recorded data is processed with the help of the custom-made softw...

Secretory Immunoglobulin A (sIgA) builds the first line of the human immune defense. It is not clear whether the power of this defence line is constant across the 24-h day, depends on sleep pressure levels and can be influenced by external lighting conditions. Thus, in 10 healthy young volunteers, we retrospectively analyzed saliva samples for sIgA...

Introduction: Diurnal variations in physical performance can affect athletes' success in competitive sports depending on whether the time of peak performance concurs with the time of competition. The purpose of this systematic review was to investigate the diurnal variation in maximum endurance and strength performance. Methods: The databases Pu...

Light exposure entrains the circadian clock through the intrinsically photosensitive retinal ganglion cells, which sense light in addition to the cone and rod photoreceptors. In congenital achromatopsia (prevalence 1:30–50,000), the cone system is non-functional, resulting in severe light avoidance and photophobia at daytime light levels. How this...

Caffeine elicits widespread effects in the central nervous system and is the most frequently consumed psychostimulant worldwide. First evidence indicates that, during daily intake, the elimination of caffeine may slow down, and the primary metabolite, paraxanthine, may accumulate. The neural impact of such adaptions is virtually unexplored. In this...

Acute caffeine intake can attenuate homeostatic sleep pressure and worsen sleep quality. Caffeine intake—particularly in high doses and close to bedtime—may also affect circadian-regulated rapid eye movement (REM) sleep promotion, an important determinant of subjective sleep quality. However, it is not known whether such changes persist under chron...

Nowadays lighting projects often include temporal variations of the light, both spectrally and in terms of intensity to consider non-visual effects of light on people. However, as of today there are no specific regulations. Compliance with common lighting standards that address visual aspects of light, often means that only little non-visually effe...

Introduction Patients with major depressive disorder (MDD) show disrupted circadian rhythms and sleep, including reduced daytime physical activity and poor sleep quality. However, previous findings are masked by psychotropic medication intake, co-morbid diseases and years of chronic mental illness. Here, we aim at identifying circadian motor activi...

Introduction Light emitted from visual displays can acutely increase alertness, improve cognitive performance and suppress melatonin in the evening. Here we tested the influence of different melanopic irradiance levels emitted by a metameric display setting on alertness, vigilance and salivary melatonin levels. Methods In an ongoing study, 37 heal...

Neuroprotective effects of caffeine have been frequently reported in the context of disease and cognitive dysfunction as well as in epidemiological studies in humans. However, evidence on caffeine effects on neural and memory functions during daily intake in a healthy cognitive state remains scarce. This randomized double-blind placebo-controlled c...

The detection of (NREM-REM) sleep cycles in human sleep data (i.e., polysomnographically assessed sleep stages) enables fine-grained analyses of ultradian variations in sleep microstructure (e.g., sleep spindles, and arousals), or other amplitude- and frequency-specific electroencephalographic features during sleep. While many laboratories have sof...

Acute caffeine intake can delay sleep initiation and reduce sleep intensity, particularly when consumed in the evening. However, it is not clear whether these sleep disturbances disappear when caffeine is continuously consumed during daytime, which is common for most coffee drinkers. To address this question, we investigated the sleep of twenty mal...

Caffeine is commonly used to combat high sleep pressure on a daily basis. However, interference with sleep–wake regulation could disturb neural homeostasis and insufficient sleep could lead to alterations in human gray matter. Hence, in this double-blind, randomized, cross-over study, we examined the impact of 10-day caffeine (3 × 150 mg/day) on hu...

Aging is associated with sleep and circadian alterations, which can negatively affect quality of life and longevity. Importantly, the age-related reduction in light sensitivity, particularly in the short-wavelength range, may underlie sleep and circadian alterations in older people. While evidence suggests that non-image-forming (NIF) light respons...

Objective This study compared the robustness of a V˙O2-plateau definition and a verification-phase protocol to day-to-day and diurnal variations in determining the true V˙O2max. Further, the additional value of a verification-phase was investigated. Methods Eighteen adults performed six cardiorespiratory fitness tests at six different times of the...

We examined whether dynamically changing light across a scheduled 16‐h waking day influences sleepiness, cognitive performance, visual comfort, melatonin secretion, and sleep under controlled laboratory conditions in healthy men. Fourteen participants underwent a 49‐h laboratory protocol in a repeated‐measures study design. They spent the first 5‐h...

The growing awareness of the biological effects of electric light on humans has stimulated ample research. New research has been devoted to lighting solutions that dynamically change their colour to mimic spectral changes of daylight. However, in some situations, the visual properties of light must be preserved, such as when working under standardi...

The detection of sleep cycles in human sleep data (i.e. polysomnographically assessed sleep stages) enables fine-grained analyses of ultradian variations in sleep microstructure (e.g. sleep spindles, and arousals), or other amplitude- and frequency-specific electroencephalographic features during sleep. While many laboratories have software that is...

Enhancing lighting conditions in institutions for individuals with dementia improves their sleep, circadian rhythms and well-being. Here, we tested whether a greater long-term daily light exposure supports the immune response to the annual influenza vaccination. Eighty older institutionalised patients suffering from dementia (54 women and 26 men) c...

Ocular light exposure has important influences on human health and well-being through modulation of circadian rhythms and sleep, as well as neuroendocrine and cognitive functions. Current patterns of light exposure do not optimally engage these actions for many individuals, but advances in our understanding of the underpinning mechanisms and emergi...

Prospective evidence on the risk of depression in relation to transportation noise exposure and noise annoyance is limited and mixed. We aimed to investigate the associations of long-term exposure to source-specific transportation noise and noise annoyance with incidence of depression in the SAPALDIA (Swiss cohort study on air pollution and lung an...