Characterizing the Modern Light Environment and its Influence on Circadian Rhythms

AbstractHumans have largely supplanted natural light cycles with a variety of artificial light sources and schedules misaligned with day-night cycles. Circadian disruption has been linked to a number of disease processes, but the extent of circadian disruption among the population is unknown. We measured light exposure and wrist temperature among residents of New York City for a full week during each of the four seasons, as well as light illuminance in nearby outdoor locations. Daily light exposure was significantly lower for individuals, compared to outdoor light sensors, for all four seasons. There was also little seasonal variation in the realized photoperiod experienced by individuals, with the only significant difference between winter and summer. We tested the hypothesis that differential light exposure impacts circadian phase timing, detected via the wrist temperature rhythm. To determine the influence of light exposure on circadian rhythms, we modeled the impact of morning, afternoon, and nighttime light exposure on the timing of the midline-estimating statistic of rhythm (MESOR). We found that morning light exposure and nighttime light exposure had a significant but opposing impact on MESOR timing. Our results demonstrate that nighttime light can shift/alter circadian rhythms to delay the morning transition from nighttime to daytime physiology, while morning light can lead to earlier onset. Our results demonstrate that circadian shifts and disruptions may be a more regular occurrence in the general population than is currently recognized. Due to the impact of circadian rhythms on health, this is convincing evidence that real-world monitoring of light exposure and circadian rhythms could lead to new advances in personalized medicine.Significance StatementDisruption of circadian rhythms has been linked to various diseases, but the prevalence of circadian disruption among the general population is unknown. Light plays a pivotal role in entraining circadian rhythms to the 24-hour day. Humans have largely supplanted natural light cycles with a variety of electric light sources and by spending large amounts of time indoors. We have shown that individuals experience a pronounced disconnect from natural light cycles. This disconnect includes low daytime light exposure, high levels of light-at-night, and minimal seasonal variation in light exposure. We identified measurable changes in wrist temperature rhythms as a function of differential light exposure during the morning and nighttime hours. Our findings suggest that circadian shifts, and even disruption, may be common in the general population.

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Characterizing the modern light environment and its influence on circadian rhythms

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2021.0721 ◽

2021 ◽

Vol 288 (1955) ◽

pp. 20210721

Author(s):

Dennis Khodasevich ◽

Susan Tsui ◽

Darwin Keung ◽

Debra J. Skene ◽

Victoria Revell ◽

...

Keyword(s):

Circadian Rhythms ◽

Light Exposure ◽

Circadian Disruption ◽

Light Sources ◽

Night Time ◽

Circadian Phase ◽

Temperature Rhythm ◽

Four Seasons ◽

Significant Difference ◽

The Impact

Humans have largely supplanted natural light cycles with a variety of electric light sources and schedules misaligned with day-night cycles. Circadian disruption has been linked to a number of disease processes, but the extent of circadian disruption among the population is unknown. In this study, we measured light exposure and wrist temperature among residents of an urban area during each of the four seasons, as well as light illuminance in nearby outdoor locations. Daily light exposure was significantly lower for individuals, compared to outdoor light sensors, across all four seasons. There was also little seasonal variation in the realized photoperiod experienced by individuals, with the only significant difference occurring between winter and summer. We tested the hypothesis that differential light exposure impacts circadian phase timing, detected via the wrist temperature rhythm. To determine the influence of light exposure on circadian rhythms, we modelled the impact of morning and night-time light exposure on the timing of the maximum wrist temperature. We found that morning and night-time light exposure had significant but opposing impacts on maximum wrist temperature timing. Our results demonstrate that, within the range of exposure seen in everyday life, night-time light can delay the onset of the maximum wrist temperature, while morning light can lead to earlier onset. Our results demonstrate that humans are minimizing natural seasonal differences in light exposure, and that circadian shifts and disruptions may be a more regular occurrence in the general population than is currently recognized.

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The Effect of Light on Sleep and Sleep-Related Physiological Factors Among Patients in Healthcare Facilities: A Systematic Review

HERD Health Environments Research & Design Journal ◽

10.1177/1937586719827946 ◽

2019 ◽

Vol 12 (4) ◽

pp. 116-141

Author(s):

Khatereh Hadi ◽

Jennifer R. Du Bose ◽

Young-Seon Choi

Keyword(s):

Light Exposure ◽

Bright Light ◽

Light Sources ◽

Related Factors ◽

Healthcare Facilities ◽

New Findings ◽

Healthcare Environments ◽

The Impact ◽

Improve Patient ◽

Bright Light Exposure

Objectives: Lighting is one of the environmental factors which can improve patient sleep in healthcare environments. Due to the high degree of variation in study designs and results on this topic, the implications have been difficult to interpret. This review consolidates studies on the impact of bright light exposure on sleep to identify lighting conditions that can be applied and researched in future healthcare environments. Methods: We searched for peer-reviewed articles on the impact of light on sleep or sleep-related outcomes in healthcare settings. We provided detailed analysis of the direct links between light and sleep, and a more cursory analysis of links between light and sleep-related factors, from 34 articles which met our inclusion criteria. Results: The current state of the literature includes evidence on how various durations and intensities of morning, midday, and evening bright light exposure, as well as whole-day light exposure interventions can improve specific aspects of sleep. Lighting interventions differed in all attributes (illuminance levels, exposure time, exposure duration, and spectral qualities) but showed promising results in improving patients’ sleep. Conclusions: Short-term bright light exposure in the morning, up to 2 hr of moderate (3,000–10,000 lux) morning exposures, up to 4 hr of moderate evening exposure, and whole-day exposures to lower illuminance levels (<3,000 lux) can improve patient sleep outcomes. Based on new findings on the mechanism through which light impacts sleep, future studies should be more specific about the spectral qualities of light sources.

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Re-Setting the Circadian Clock Using Exercise against Sarcopenia

International Journal of Molecular Sciences ◽

10.3390/ijms21093106 ◽

2020 ◽

Vol 21 (9) ◽

pp. 3106 ◽

Cited By ~ 4

Author(s):

Youngju Choi ◽

Jinkyung Cho ◽

Mi-Hyun No ◽

Jun-Won Heo ◽

Eun-Jeong Cho ◽

...

Keyword(s):

Skeletal Muscle ◽

Circadian Rhythms ◽

Circadian Clock ◽

Intervention Strategy ◽

Muscle Metabolism ◽

Circadian Disruption ◽

Adverse Health Outcomes ◽

Exercise Timing ◽

Underlying Mechanisms ◽

The Impact

Sarcopenia is defined as the involuntary loss of skeletal muscle mass and function with aging and is associated with several adverse health outcomes. Recently, the disruption of regular circadian rhythms, due to shift work or nocturnal lifestyle, is emerging as a novel deleterious factor for the development of sarcopenia. The underlying mechanisms responsible for circadian disruption-induced sarcopenia include molecular circadian clock and mitochondrial function associated with the regulation of circadian rhythms. Exercise is a potent modulator of skeletal muscle metabolism and is considered to be a crucial preventative and therapeutic intervention strategy for sarcopenia. Moreover, emerging evidence shows that exercise, acting as a zeitgeber (time cue) of the skeletal muscle clock, can be an efficacious tool for re-setting the clock in sarcopenia. In this review, we provide the evidence of the impact of circadian disruption on skeletal muscle loss resulting in sarcopenia. Furthermore, we highlight the importance of exercise timing (i.e., scheduled physical activity) as a novel therapeutic strategy to target circadian disruption in skeletal muscle.

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Telling the Time with a Broken Clock: Quantifying Circadian Disruption in Animal Models

Biology ◽

10.3390/biology8010018 ◽

2019 ◽

Vol 8 (1) ◽

pp. 18 ◽

Cited By ~ 6

Author(s):

Laurence Brown ◽

Angus Fisk ◽

Carina Pothecary ◽

Stuart Peirson

Keyword(s):

Circadian Rhythms ◽

Light Exposure ◽

Circadian Disruption ◽

Jet Lag ◽

Light Phase ◽

Potential Therapeutic Target ◽

Normal Ranges ◽

Activity Onset ◽

Periodogram Analysis ◽

Phase Activity

Circadian rhythms are approximately 24 h cycles in physiology and behaviour that enable organisms to anticipate predictable rhythmic changes in their environment. These rhythms are a hallmark of normal healthy physiology, and disruption of circadian rhythms has implications for cognitive, metabolic, cardiovascular and immune function. Circadian disruption is of increasing concern, and may occur as a result of the pressures of our modern 24/7 society—including artificial light exposure, shift-work and jet-lag. In addition, circadian disruption is a common comorbidity in many different conditions, ranging from aging to neurological disorders. A key feature of circadian disruption is the breakdown of robust, reproducible rhythms with increasing fragmentation between activity and rest. Circadian researchers have developed a range of methods for estimating the period of time series, typically based upon periodogram analysis. However, the methods used to quantify circadian disruption across the literature are not consistent. Here we describe a range of different measures that have been used to measure circadian disruption, with a particular focus on laboratory rodent data. These methods include periodogram power, variability in activity onset, light phase activity, activity bouts, interdaily stability, intradaily variability and relative amplitude. The strengths and limitations of these methods are described, as well as their normal ranges and interrelationships. Whilst there is an increasing appreciation of circadian disruption as both a risk to health and a potential therapeutic target, greater consistency in the quantification of disrupted rhythms is needed.

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Seasonal Variation in Migraine

Cephalalgia ◽

10.1111/j.1468-2982.2005.01018.x ◽

2005 ◽

Vol 25 (10) ◽

pp. 811-816 ◽

Cited By ~ 37

Author(s):

KB Alstadhaug ◽

R Salvesen ◽

SI Bekkelund

Keyword(s):

Seasonal Variation ◽

Sleep Disturbances ◽

Light Exposure ◽

Light Conditions ◽

Circadian Variations ◽

Polar Night ◽

Seasonal Periodicity ◽

Frequent Use ◽

Arctic Area ◽

The Impact

Our group has previously shown that migraineurs, as opposed to individuals with other headaches, are more likely to have headache during the bright arctic summer than during the polar night season. We set out to investigate the impact of seasonal light exposure in migraine with and without aura. We performed a questionnaire-based study of 169 female volunteer migraineurs in an arctic area where light conditions during summer and winter seasons are extreme. We included 98 patients with migraine with aura (MA) and 71 with migraine without aura (MoA). One hundred and seven patients (63%) reported seasonal variation in migraine attack frequency. Close to half (47%) of patients with aura, but only 17% of patients without aura, reported more frequent attacks during the light season ( P < 0.001). Patients with MA reported interictal light hypersensitivity and light exposure as an attack precipitating factor significantly more often than individuals with MoA. They also reported significantly more frequent use of sunglasses to prevent attacks. We found no significant differences between MA and MoA as regards sleep disturbances, use of oral contraceptives, impact of headache or circadian variations. Seasonal periodicity of migraine in an arctic population with more frequent attacks during the light season is a convincing phenomenon in MA but not in MoA. The amount of light exposure seems to be pivotal to this variation.

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Let there be blue-depleted light: in-patient dark therapy, circadian rhythms and length of stay

BJPsych Advances ◽

10.1192/bja.2020.47 ◽

2020 ◽

pp. 1-12 ◽

Cited By ~ 1

Author(s):

Jan Scott ◽

Knut Langsrud ◽

Ingunn Ro Goulding ◽

Havard Kallestad

Keyword(s):

Circadian Rhythms ◽

Sleep Disturbances ◽

Light Exposure ◽

Environmental Influence ◽

Time Of Day ◽

Circadian System ◽

Temporal Organization ◽

Night Time ◽

Inpatient Psychiatric Care ◽

The Impact

SUMMARY Light is the most important environmental influence (zeitgeber) on the synchronization of the circadian system in humans. Excess light exposure during the evening and night-time affects secretion of the hormone melatonin, which in turn modifies the temporal organization of circadian rhythms, including the sleep–wake cycle. As sleep disturbances are prominent in critically ill medical and psychiatric patients, researchers began to examine the impact of light exposure on clinical outcomes and length of hospitalization. In psychiatric inpatients, exposure to bright morning light or use of blue blocking glasses have proved useful interventions for mood disorders. Recently, knowledge about light and the circadian system has been applied to the design of inpatient facilities with dynamic lighting systems that change according to time of day. The installation of ‘circadian lighting’ alongside technologies for monitoring sleep–wake patterns could prove to be one of the most practical and beneficial innovations in inpatient psychiatric care for more than half a century.

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Exploring the Impact of Natural Light Exposure on Sleep of Healthy Older Adults: A Field Study

Journal of Daylighting ◽

10.15627/jd.2018.2 ◽

2018 ◽

Vol 5 (1) ◽

pp. 14-20 ◽

Cited By ~ 2

Author(s):

Mariëlle P. J. Aarts ◽

◽

Janny C. Stapel ◽

Toine A. M. C. Schoutens ◽

Joost van Hoof ◽

...

Keyword(s):

Older Adults ◽

Field Study ◽

Light Exposure ◽

Natural Light ◽

Healthy Older Adults ◽

The Impact

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Mathematical analysis of circadian disruption and metabolic re-entrainment of hepatic gluconeogenesis: the intertwining entraining roles of light and feeding

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00271.2017 ◽

2018 ◽

Vol 314 (6) ◽

pp. E531-E542 ◽

Cited By ~ 6

Author(s):

Seul-A Bae ◽

Ioannis P. Androulakis

Keyword(s):

Circadian Rhythms ◽

Metabolic Activity ◽

Driving Forces ◽

Gene Knockout ◽

Experimental Studies ◽

Circadian Disruption ◽

Hepatic Gluconeogenesis ◽

Uncertainty Analyses ◽

The Impact ◽

The Relationship

The circadian rhythms influence the metabolic activity from molecular level to tissue, organ, and host level. Disruption of the circadian rhythms manifests to the host’s health as metabolic syndromes, including obesity, diabetes, and elevated plasma glucose, eventually leading to cardiovascular diseases. Therefore, it is imperative to understand the mechanism behind the relationship between circadian rhythms and metabolism. To start answering this question, we propose a semimechanistic mathematical model to study the effect of circadian disruption on hepatic gluconeogenesis in humans. Our model takes the light-dark cycle and feeding-fasting cycle as two environmental inputs that entrain the metabolic activity in the liver. The model was validated by comparison with data from mice and rat experimental studies. Formal sensitivity and uncertainty analyses were conducted to elaborate on the driving forces for hepatic gluconeogenesis. Furthermore, simulating the impact of Clock gene knockout suggests that modification to the local pathways tied most closely to the feeding-fasting rhythms may be the most efficient way to restore the disrupted glucose metabolism in liver.

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Accuracy of the GENEActiv Device for Measuring Light Exposure in Sleep and Circadian Research

Clocks & Sleep ◽

10.3390/clockssleep2020012 ◽

2020 ◽

Vol 2 (2) ◽

pp. 143-152

Author(s):

Julia E. Stone ◽

Elise M. McGlashan ◽

Elise R. Facer-Childs ◽

Sean W. Cain ◽

Andrew J. K. Phillips

Keyword(s):

Light Source ◽

Light Exposure ◽

Red Light ◽

Spectral Composition ◽

Green Light ◽

Well Being ◽

Infrared Light ◽

Light Sources ◽

Lower Accuracy ◽

The Impact

Light is a variable of key interest in circadian rhythms research, commonly measured using wrist-worn sensors. The GENEActiv Original is a cost-effective and practical option for assessing light in ambulatory settings. With increasing research on health and well-being incorporating sleep and circadian factors, the validity of wearable devices for assessing light environments needs to be evaluated. In this study, we tested the accuracy of the GENEActiv Original devices (n = 10) for recording light under a range of ecologically relevant lighting conditions, including LED, fluorescent, infrared, and outdoor lighting. The GENEActiv output had a strong linear relationship with photopic illuminance. However, the devices consistently under-reported photopic illuminance, especially below 100 lux. Accuracy below 100 lux depended on the light source, with lower accuracy and higher variability under fluorescent lighting. The device’s accuracy was also tested using light sources of varying spectral composition, which indicated that the device tends to under-report photopic illuminance for green light sources and over-report for red light sources. Furthermore, measures of photopic illuminance were impacted by infrared light exposure. We conclude that the GENEActiv Original is suitable for mapping light patterns within an individual context, and can reasonably differentiate indoor vs. outdoor lighting, though the accuracy is variable at low light conditions. Given the human circadian system’s high sensitivity to light levels below 100 lux, if using the GENEActiv Original, we recommend also collecting light source data to better understand the impact on the circadian system, especially where participants spend prolonged periods in dim lighting.

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