Rhythms of light: Understanding the role of circadian timing in alertness and cognitive performance.

The nonimage-forming effects of light are pivotal in regulating cognitive functions, including alertness, sustained attention, and higher-order cognitive processes. These cognitive domains are deeply influenced by the sleep-wake cycle, which are governed by two key processes: the homeostatic process, which builds sleep pressure during wakefulness, and the circadian process, which aligns with environmental light cues to regulate wakefulness and sleep. When these processes fall out of sync-a condition known as circadian misalignment-alertness, sustained attention, and cognitive performance can suffer significantly.

Adverse effects of late sleep on physical health in a large cohort of community-dwelling adults.

Aims: Sleep timing, influenced by chronotype, behavior, and circadian rhythms, is critical for human health. While previous research has linked chronotype to various health outcomes, the impact of aligning sleep timing with chronotype on physical health remains underexplored. The objective of this study is to investigate the association between chronotype, actual sleep timing, and their alignment with a spectrum of physical health outcomes.

How stepping out helped us tune in: finding space and time to as an early career researcher.

The transition from postdoc to junior faculty is exciting and uniquely challenging. On one hand, it allows for increased creative freedom and the opportunity to grow into an independent scientist. On the other hand, it comes with increasing administrative responsibilities, feelings of isolation, and high pressure to perform.

How many days are enough? Sleep-wake timing regularity and fragmentation scores change with the number of days included.

The duration of sleep data collection from actigraphy is often influenced by practical factors (e.g. workdays versus non-workdays), but the impact of the variation of duration on outcome measures of interest has not been well explored.

Perils of the nighttime: Impact of behavioral timing and preference on mental health in 73,888 community-dwelling adults.

Mental health is independently influenced by the inclination to sleep at specific times (chronotype) and the actual sleep timing (behavior). Chronotype and timing of actual sleep are, however, often misaligned. This study aims to determine how chronotype, sleep timing, and the alignment between the two impact mental health.

Sex differences in sleep, circadian rhythms, and metabolism: Implications for precision medicine.

The number of individuals experiencing sleep loss has exponentially risen over the past decades. Extrapolation of laboratory findings to the real world suggests that females are more affected by extended wakefulness and circadian misalignment than males are. Therefore, long-term effects such as sleep and metabolic disorders are likely to be more prevalent in females than in males.

The sleep-circadian interface: A window into mental disorders.

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 exacerbate poor sleep and disrupt clock-controlled processes.

Fatigued but not sleepy? An empirical investigation of the differentiation between fatigue and sleepiness in sleep disorder patients in a cross-sectional study.

Objective: Sleepiness and fatigue are common complaints among individuals with sleep disorders. The two concepts are often used interchangeably, causing difficulty with differential diagnosis and treatment decisions. The current study investigated sleep disorder patients to determine which factors best differentiated sleepiness from fatigue.

Impaired 24-h activity patterns are associated with an increased risk of Alzheimer's disease, Parkinson's disease, and cognitive decline.

Background: Sleep-wake regulating circuits are affected during prodromal stages in the pathological progression of both Alzheimer's disease (AD) and Parkinson's disease (PD), and this disturbance can be measured passively using wearable devices. Our objective was to determine whether accelerometer-based measures of 24-h activity are associated with subsequent development of AD, PD, and cognitive decline.

Methods: This study obtained UK Biobank data from 82,829 individuals with wrist-worn accelerometer data aged 40 to 79 years with a mean (± SD) follow-up of 6.

ENLIGHT: A consensus checklist for reporting laboratory-based studies on the non-visual effects of light in humans.

Background: There is no consensus on reporting light characteristics in studies investigating non-visual responses to light. This project aimed to develop a reporting checklist for laboratory-based investigations on the impact of light on non-visual physiology.

Methods: A four-step modified Delphi process (three questionnaire-based feedback rounds and one face-to-face group discussion) involving international experts was conducted to reach consensus on the items to be included in the checklist.

Moving time zones in a flash with light therapy during sleep.

In humans, exposure to continuous light is typically used to change the timing of the circadian clock. This study examines the efficiency of a sequence of light flashes ("flash therapy") applied during sleep to shift the clock. Healthy participants (n = 10) took part in two 36-h laboratory stays, receiving a placebo (goggles, no light) during one visit and the intervention (goggles, 2-ms flashes broad-spectrum light for 60 min, delivered every 15 s, starting 30 min after habitual sleep onset) during the other.

The Impact of Missing Data and Imputation Methods on the Analysis of 24-Hour Activity Patterns.

The purpose of this study is to characterize the impact of the timing and duration of missing actigraphy data on interdaily stability (IS) and intradaily variability (IV) calculation. The performance of three missing data imputation methods (linear interpolation, mean time of day (ToD), and median ToD imputation) for estimating IV and IS was also tested. Week-long actigraphy records with no non-wear or missing timeseries data were masked with zeros or 'Not a Number' (NaN) across a range of timings and durations for single and multiple missing data bouts.

Circadian photoreception: The impact of light on human circadian rhythms.

Light is the preeminent external influence in determining the position of the internal circadian clock relative to the outside world. In this chapter, we discuss the different parameters of light that impact how it influences the human circadian clock. We detail how the timing (phase), intensity, duration and temporal structure, and spectral composition all can modulate the impact of light on both the timing of the circadian clock as well as its amplitude.

Impact of daytime spectral tuning on cognitive function.

Light at night can improve alertness and cognition. Exposure to daytime light, however, has yielded less conclusive results. In addition to direct effects, daytime light may also mitigate the impact of nocturnal light exposure on alertness.

Objective underpinnings of self-reported sleep quality in middle-aged and older adults: The importance of N2 and wakefulness.

Study Objectives: The measurable aspects of brain function (polysomnography, PSG) that are correlated with sleep satisfaction are poorly understood. Using recent developments in automated sleep scoring, which remove the within- and between-rater error associated with human scoring, we examine whether PSG measures are associated with sleep satisfaction.

Design And Setting: A single night of PSG data was compared to contemporaneously collected measures of sleep satisfaction with Random Forest regressions.

Physiological correlates of the Epworth Sleepiness Scale reveal different dimensions of daytime sleepiness.

The Epworth Sleepiness Scale is commonly used to examine self-reported daytime sleepiness in clinical populations; the physiologic correlates of this scale, however, are not well understood. Furthermore, how well this scale correlates with parallel objective and self-reported concepts of daytime sleepiness is not well described. As such, we used machine learning algorithms to examine the association between Epworth Sleepiness Scale scores and 55 sleep and medical variables in the Sleep Heart Health Study ( = 2105).

A Temporal Threshold for Distinguishing Off-Wrist from Inactivity Periods: A Retrospective Actigraphy Analysis.

(1) Background. To facilitate accurate actigraphy data analysis, inactive periods have to be distinguished from periods during which the device is not being worn. The current analysis investigates the degree to which off-wrist and inactive periods can be automatically identified.

Deep Brain Stimulation in the Nucleus Accumbens for Binge Eating Disorder: a Study in Rats.

Binge eating disorder (BED), with its compulsive and addictive components, may often underlie weight regain after gastrointestinal bariatric surgeries. BED is therefore considered an exclusion criterion for these surgeries. Anecdotal reports suggest that deep brain stimulation (DBS) is an effective treatment for addictive disorders with, similar to BED, pathological changes in cerebral reward circuitry.

Daytime melatonin and light independently affect human alertness and body temperature.

Light significantly improves alertness during the night (Cajochen, Sleep Med Rev, 11, 2007 and 453; Ruger et al., AJP Regul Integr Comp Physiol, 290, 2005 and R1413), but results are less conclusive at daytime (Lok et al., J Biol Rhythms, 33, 2018 and 589).

White Light During Daytime Does Not Improve Alertness in Well-rested Individuals.

Broad-spectrum light applied during the night has been shown to affect alertness in a dose-dependent manner. The goal of this experiment was to investigate whether a similar relationship could be established for light exposure during daytime. Fifty healthy participants were subjected to a paradigm (0730-1730 h) in which they were intermittently exposed to 1.

Light, Alertness, and Alerting Effects of White Light: A Literature Overview.

Light is known to elicit non-image-forming responses, such as effects on alertness. This has been reported especially during light exposure at night. Nighttime results might not be translatable to the day.