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Blume, Garbazza & Spitschan, 2019

Effects of light on human circadian rhythms, sleep and mood.
Somnologie, 23, 147–156. DOI: 10.1007/s11818-019-00215-x

A useful peer-reviewed overview of how light affects circadian rhythms, sleep and mood. The authors are associated with the Centre for Chronobiology at the University of Basel, making it particularly relevant in the Swiss context.

 

Brown et al., 2022

Recommendations for daytime, evening, and nighttime indoor light exposure to best support physiology, sleep, and wakefulness in healthy adults.
PLOS Biology, 20(3), e3001571. DOI: 10.1371/journal.pbio.3001571

An international expert consensus recommending substantially more light during the day, much lower melanopic light before sleep, and very low light during the sleep period. It provides strong support for Restwell's emphasis on a clear day-evening-night light pattern.

 

Cajochen et al., 2011

Evening exposure to a light-emitting diodes (LED)-backlit computer screen affects circadian physiology and cognitive performance.
Journal of Applied Physiology, 110, 1432–1438. DOI: 10.1152/japplphysiol.00165.2011
A controlled human experiment showing that evening exposure to a blue-enriched LED display affected melatonin, subjective sleepiness and EEG measures of sleepiness compared with a different spectral condition.

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Phillips et al., 2019
High sensitivity and interindividual variability in the response of the human circadian system to evening light.
Proceedings of the National Academy of Sciences, 116(24), 12019–12024. DOI: 10.1073/pnas.1901824116

A controlled human study showing that relatively low evening light levels can suppress melatonin, with substantial differences in sensitivity between individuals. The findings support reducing evening light exposure and help explain why the same lighting environment may affect people differently.

 

Chang et al., 2015
Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness.
Proceedings of the National Academy of Sciences, 112(4), 1232–1237. DOI: 10.1073/pnas.1418490112

A randomised crossover experiment showing that prolonged evening reading on a light-emitting device suppressed melatonin, delayed circadian timing and reduced next-morning alertness compared with reading a printed book. The extended exposure used in the experiment should be considered when applying its findings to everyday screen use.

 

Hartstein et al., 2022
High sensitivity of melatonin suppression response to evening light in preschool-aged children.
Journal of Pineal Research, 72(2), e12780. DOI: 10.1111/jpi.12780

An experimental study showing substantial melatonin suppression in preschool children exposed to evening light, including relatively low intensities. The children had previously spent an extended period in dim light, which affects how the results should be interpreted. The findings support particular care with lighting before children’s bedtime.

 

Münch et al., 2017
Blue-Enriched Morning Light as a Countermeasure to Light at the Wrong Time: Effects on Cognition, Sleepiness, Sleep, and Circadian Phase.
Neuropsychobiology, 74(4), 207–218. DOI: 10.1159/000477093

A small controlled study showing that bright, blue-enriched morning light helped stabilise circadian timing under challenging daytime and evening lighting conditions. It illustrates the importance of exposure timing and supports adequate morning light as part of a consistent daily light–dark pattern.

 

Mason et al., 2022
Light exposure during sleep impairs cardiometabolic function.
Proceedings of the National Academy of Sciences, 119(12), e2113290119. DOI: 10.1073/pnas.2113290119

A controlled laboratory study showing that one night of sleeping under moderate room lighting increased nighttime heart rate and next-morning insulin resistance compared with sleeping in dim light. It demonstrates short-term physiological effects and supports reducing unnecessary illumination during sleep; long-term disease outcomes were not measured.

 

Cheung et al., 2016
Morning and Evening Blue-Enriched Light Exposure Alters Metabolic Function in Normal Weight Adults.
PLOS ONE, 11(5), e0155601. DOI: 10.1371/journal.pone.0155601

A small laboratory study reporting changes in insulin responses during blue-enriched light exposure, with a higher glucose peak during evening exposure. It provides experimental evidence that lighting can influence metabolic regulation. Brightness and spectrum changed together, so the effects cannot be attributed to blue wavelengths alone.

 

Windred et al., 2024 — Type 2 diabetes
Personal light exposure patterns and incidence of type 2 diabetes: analysis of 13 million hours of light sensor data and 670,000 person-years of prospective observation.
The Lancet Regional Health – Europe, 42, 100943. DOI: 10.1016/j.lanepe.2024.100943

A large prospective study using wrist-worn light sensors in approximately 85,000 adults. Brighter nighttime exposure was associated with a higher subsequent risk of type 2 diabetes, including after adjustment for several lifestyle and health factors. The findings support nighttime light reduction as a reasonable precaution, while causation remains incompletely established.

 

Windred et al., 2025 — Cardiovascular disease
Light Exposure at Night and Cardiovascular Disease Incidence.
JAMA Network Open, 8(10), e2539031. DOI: 10.1001/jamanetworkopen.2025.39031

A prospective study of approximately 89,000 adults linking brighter personally measured nighttime light exposure with higher subsequent risks of coronary artery disease, heart attack, heart failure, atrial fibrillation and stroke. Associations remained after adjustment for multiple risk factors, although the observational design cannot establish that reducing light prevents these conditions.

 

Windred et al., 2024 — Mortality
Brighter nights and darker days predict higher mortality risk: A prospective analysis of personal light exposure in >88,000 individuals.
Proceedings of the National Academy of Sciences, 121(43), e2405924121. DOI: 10.1073/pnas.2405924121

A large prospective study associating brighter nighttime exposure with higher mortality and brighter daytime exposure with lower mortality. Personal light measurements strengthen the exposure assessment, but a single measurement week and possible residual confounding limit causal interpretation. The findings support further investigation of the daily light–dark pattern as a modifiable health factor.

 

Park et al., 2019
Association of Exposure to Artificial Light at Night While Sleeping With Risk of Obesity in Women.
JAMA Internal Medicine, 179(8), 1061–1071. DOI: 10.1001/jamainternmed.2019.0571

A prospective study of more than 43,000 women finding that sleeping with a television or light on in the room was associated with subsequent weight gain and obesity. Exposure was self-reported, and other behavioural factors may contribute. The study adds human evidence to concerns about nighttime lighting and metabolic health.

 

Burns et al., 2023
Day and night light exposure are associated with psychiatric disorders: an objective light study in >85,000 people.
Nature Mental Health, 1, 853–862. DOI: 10.1038/s44220-023-00135-8

A large observational study linking brighter nighttime light with several psychiatric outcomes, while brighter daytime exposure was associated with more favourable outcomes. The findings support the relevance of daily lighting patterns to mental health, although psychiatric conditions can themselves alter sleep, behaviour and light exposure.

 

National Toxicology Program, 2021
NTP Cancer Hazard Assessment Report on Night Shift Work and Light at Night.
US National Toxicology Program. DOI: 10.22427/NTP-CHR-NSWLAN

A systematic assessment integrating human, animal and mechanistic research. NTP concluded that there is moderate confidence in a causal relationship between cancer and excessive nighttime light combined with insufficient daylight when these conditions cause circadian disruption. Human epidemiological evidence for indoor or outdoor light exposure alone was considered inadequate, so the assessment does not quantify cancer risk from ordinary household lighting.

Research context: The Windred and Burns studies above draw on overlapping UK Biobank participants. They examine different outcomes but should not be counted as independent population replications.

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CIE, 2022

Visual Aspects of Time-Modulated Lighting Systems
The International Commission on Illumination notes that temporal light modulation can reduce performance, increase fatigue and contribute to acute effects including migraine episodes.

 

Wilkins et al., 1989 

Fluorescent lighting, headaches and eyestrain
In a double-blind crossover study of office workers, headache and eyestrain incidence was more than halved under high-frequency lighting with much lower 100 Hz modulation compared with conventionally ballasted fluorescent lighting.

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Fisher et al., 2022 

Visually sensitive seizures: An updated review by the Epilepsy Foundation
The review reports that flashing light and other visual stimuli can provoke seizures in susceptible individuals, with particular risk from flashes in the roughly 3–60 Hz range, especially around 15–20 Hz. PMID: 35132632

 

Fisher et al., 2005

Photic- and pattern-induced seizures: expert consensus of the Epilepsy Foundation of America Working Group
This expert consensus describes flashing light as a seizure risk under defined conditions of frequency, brightness and visual-field coverage, and provides thresholds intended to reduce the risk of photosensitive seizures.  PMID: 16146438

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