Effects of outdoor artificial light at night on human health and behavior: A literature review

The association between outdoor artificial light at night exposure and antenatal depression and anxiety symptoms: A retrospective cohort study in China

BACKGROUND

Outdoor artificial light at night (ALAN) has emerged as a significant source of environmental pollution, however its association with antenatal depression and anxiety symptoms has been rarely explored before.

METHODS

This study was based on a cohort study conducted at the Maternal and Child Health Care Center in Ma'anshan City, Anhui Province, China, which ultimately included 1047 pregnant women. Depression and anxiety symptoms were evaluated utilizing the self-administered Patient Health Questionnaire (PHQ-9) and the 7-item Generalized Anxiety Scale (GAD-7), respectively. Exposure levels to outdoor ALAN were calculated utilizing satellite data and the participants' usual addresses. Logistic regression and restricted cubic spline were used to assess the association between exposure to outdoor ALAN and depression and anxiety symptoms in pregnant women.

RESULTS

After adjusting for confounding factors, high ALAN exposure during the pre-pregnancy period (ORdepression = 3.16, 95% CI: 1.14-8.75; ORanxiety = 3.09, 95% CI: 1.51-6.28) and first trimester (ORdepression = 2.90, 95% CI: 1.13-7.45; ORanxiety = 3.11, 95% CI: 1.55-6.25) were associated with increased risks of antenatal depression and anxiety symptoms. Restricted cubic spline analyses showed the above associations were not nonlinear.

CONCLUSION

Our study is the first to propose that exposure to high levels of outdoor ALAN three months before pregnancy and during the first trimester of pregnancy is a risk factor for antenatal depression and anxiety symptoms.

Artificial light at night impairs visual lateralisation in a fish

Environmental light, particularly during early development, significantly influences lateralisation, the asymmetric information processing between brain hemispheres. We hypothesised that lateralisation could be affected by artificial light at night (ALAN), a widespread form of environmental pollution. In our experiment, we exposed eggs and larvae of zebrafish to either control or ALAN conditions and then tested them in a rotational test to assess motor lateralisation, and a mirror test to assess lateralisation in response to visual stimuli. The control group exhibited a significant lateralisation bias at the population level, prioritising the processing of visual information with their right hemisphere. In contrast, the zebrafish exposed to ALAN did not show this bias, leading to a notable reduction in lateralisation. Additionally, we found evidence of reduced individual differences in lateralisation in the ALAN group. Overall, our findings demonstrate that ALAN disrupts the natural lateralisation in fish larvae, possibly affecting their behaviour and survival.

Sleep Capital: Linking Brain Health to Wellbeing and Economic Productivity Across the Lifespan

INTRODUCTION AND FRAMEWORK

Sleep capital contributes to individual and societal wellbeing, productivity, and economic outcomes and involves a novel aspect of brain capital. It encompasses the quality and quantity of sleep as integral components that influence cognitive abilities, mental and brain health, and physical health, affecting workplace productivity, learning, decision-making, and overall economic performance. Here, we bring a framework to understand the complex relationship between sleep quality, health, wellbeing, and economic productivity. Then we outline the multilevel impact of sleep on cognitive abilities, mental/brain health, and economic indicators, providing evidence for the substantial returns on investment in sleep health initiatives. Moreover, sleep capital is a key factor when considering brain health across the lifespan, especially for the aging population.

DISCUSSION

We propose specific elements and main variables to develop specific indexes of sleep capital to address its impacts on health, wellbeing and productivity.

CONCLUSION

Finally, we suggest policy recommendations, workplace interventions, and individual strategies to promote sleep health and brain capital. Investing in sleep capital is essential for fostering a healthier, happier, fairer and more productive society.

Light pollution regulations and where to find them

The growing concerns about the adverse impacts of light pollution on astronomy, the environment, biodiversity, human health, and energy use have brought increased attention to the issue on legal and political agendas. Various international frameworks and governments at different levels have taken action to mitigate the impacts of nighttime lighting. This article provides an overview of regulatory instruments adopted to protect the nocturnal environment, explaining triggers for regulatory changes, using an interdisciplinary perspective. It proposes a classification of these instruments based on their nature: (1) law or policy, (2) binding or non-binding, and by their (3) levels and (4) areas of implementation, supported by specific examples. The article identifies current shortcomings and recommends future regulatory changes to address light pollution effectively. This interdisciplinary research aims to provide a better understanding of light pollution as an environmental concern and explains the development of light pollution regulations, helping to foster interdisciplinary communication and the adoption of more adequate regulatory measures to address light pollution. Additionally, this study intends to fill the gap in legal and policy research related to light pollution.

Exposure to green space, nighttime light, air pollution, and noise and cardiovascular disease risk: a prospective cohort study

Current literature lacks information regarding impacts of green spaces on susceptibility to cardiovascular disease (CVD) related to harmful environmental exposures. The UK Biobank cohort study was utilized to investigate whether green spaces can mitigate risks associated with air pollutants, nighttime light, noise, and traffic intensity. Latent Profile Analysis was performed on green spaces and adverse environmental exposures in order to assess individual level exposure. Cox proportional risk models were employed to calculate hazard ratios for the risk of cerebrovascular diseases related to individual and joint adverse environmental exposures. Among participants in domestic garden group (DGG, higher proportion of domestic garden and lower proportion of other green space), adverse environmental exposures was associated with increased risks of cerebrovascular disease. However, these associations were no longer observed in other green space group (GSG, lower proportion of domestic garden and higher proportion of other green space). Interestingly the opposite effect occurred in participants with heart failure (HF) onset, where adverse environmental exposures were associated with increased risk of HF in GSG, and these associations were no longer observed in DGG. Domestic gardens may mitigate the risk of HF caused by adverse environmental exposures, and natural and water environments may offset the risk of cerebrovascular disease. Consequently, there are policy implications for improving urban green space planning to maximize their protective effects.

Sleep problems mediate the association between outdoor nighttime light and symptoms of depression and anxiety: A cross-sectional, multi-city study in Bulgaria

BACKGROUND

Nighttime light is a growing anthropogenic health threat, particularly in urban areas. Limited evidence suggests that exposure to outdoor artificial light at night (ALAN) may be associated with people's mental health by disrupting sleep-wake cycles.

AIMS

We assessed 1) the association between ALAN exposure and adults' symptoms of depression and anxiety, 2) whether the association was modified by sex, age, and income, and 3) the mediating role of sleep problems.

METHODS

We obtained cross-sectional data from 4,068 adults from the five largest Bulgarian cities. Depression and anxiety symptoms were measured using the 4-item Patient Health Questionnaire (PHQ-4). Sleep problems were self-reported based on three items. Outdoor ALAN at residential addresses was assessed using annual radiance levels obtained from satellite imagery. Regression models were adjusted for person-level characteristics, green space, and nitrogen dioxide (NO2). We also assessed effect modification by sex, age, and income. Using mediation analyses, we tested sleep problems as a mediator of the ALAN-PHQ-4 association.

RESULTS

Greater ALAN exposure in the fully adjusted model was marginally associated with higher PHQ-4 scores. We observed no effect modification. The mediator, sleep problems, was also positively associated with ALAN. The mediation of sleep problems was significantly positive. While the direct association was null, the total ALAN association was marginally and positively associated with PHQ-4 scores.

CONCLUSIONS

Our findings suggest a positive association between outdoor nighttime light pollution and mental health. Poor sleep quality is a possible pathway relating ALAN exposure to mental health. Considering the increasing ubiquity and intensity of urban nighttime illumination, light pollution-reducing policies may provide significant health benefits for urban populations.

Quality analysis of photometers using vertical window illuminance measurements

In urban areas, one of the main forms of light pollution is the intrusion of light through windows into residential buildings. This phenomenon can harm human health, so standards have been introduced to define limits for vertical illuminance. This study aims to assess the levels of outdoor lighting on the windows of residential buildings in Poland in terms of compliance with standards for protection against intrusive light, as well as to compare the results obtained using various commercially available photometers. The paper presents the results of field measurements of vertical illuminance on the window surfaces of 17 residential buildings in several cities in Poland. The measurements were made with 22 photometers representing different metrological levels. The measuring instruments selected for the study are a sample of commercially available photometers. Despite the same lighting conditions on the surface of the individual windows, discrepancies can be seen in the measured illuminance values of the different photometers. The vertical illuminance measurements were subjected to statistical analysis. It was found that of the 22 photometers, only a few were suitable for assessing obtrusive light from outdoor lighting installations. It has also been noted that on window surfaces, in buildings located on a busy street in the city centre, the illuminance can reach up to 100 lx, many times exceeding the permissible values of 1, 2, 5, 10 and 25 lx.

Interactive correlations between artificial light at night, health risk behaviors, and cardiovascular health among patients with diabetes: A cross-sectional study

BACKGROUND

Artificial light at night (ALAN) is a common phenomenon and contributes to the severe light pollution suffered by more than 80% of the world's population. This study aimed to evaluate the relationship between outdoor ALAN exposure and cardiovascular health (CVH) in patients with diabetes and the influence of various modifiable factors.

METHODS

A survey method based on the China Diabetes and Risk Factor Monitoring System was adopted. Study data were extracted for 1765 individuals with diabetes in Anhui Province. Outdoor ALAN exposure (nW/cm2/sr) within 1000 m of each participant's residential address was obtained from satellite imagery data, with a resolution of ~1000 m. Health risk behaviors (HRBs) were measured via a standardized questionnaire. A linear regression model was employed to estimate the relationship between outdoor ALAN, HRBs, and CVH.

RESULTS

Participants' mean age was 59.10 ± 10.0 years. An association was observed between ALAN and CVH in patients with diabetes (β = 0.205) and exercise (β = -1.557), moderated by HRBs, or metabolic metrics. There was an association between ALAN, ALAN, vegetable intake, and CVH.

CONCLUSIONS

Exploring the relationship between ALAN exposure and cardiovascular and metabolic health provides policy data for improving light pollution strategies and reducing the risk of cardiovascular and metabolic disease in patients with diabetes.

Artificial Light at Night and Type 2 Diabetes Mellitus

The widespread and pervasive use of artificial light at night (ALAN) in our modern 24-hour society has emerged as a substantial disruptor of natural circadian rhythms, potentially leading to a rise in unhealthy lifestyle-related behaviors (e.g., poor sleep; shift work). This phenomenon has been associated with an increased risk of type 2 diabetes mellitus (T2DM), which is a pressing global public health concern. However, to date, reviews summarizing associations between ALAN and T2DM have primarily focused on the limited characteristics of exposure (e.g., intensity) to ALAN. This literature review extends beyond prior reviews by consolidating recent studies from 2000 to 2024 regarding associations between both indoor and outdoor ALAN exposure and the incidence or prevalence of T2DM. We also described potential biological mechanisms through which ALAN modulates glucose metabolism. Furthermore, we outlined knowledge gaps and investigated how various ALAN characteristics beyond only light intensity (including light type, timing, duration, wavelength, and individual sensitivity) influence T2DM risk. Recognizing the detrimental impact of ALAN on sleep health and the behavioral correlates of physical activity and dietary patterns, we additionally summarized studies investigating the potential mediating role of each component in the relationship between ALAN and glucose metabolism. Lastly, we proposed implications of chronotherapies and chrononutrition for diabetes management in the context of ALAN exposure.

Real-ambient bedroom light at night increases systemic inflammation and disrupts circadian rhythm of inflammatory markers

BACKGROUND

Exposure to light at night (LAN) has been associated with multiple adverse health outcomes. However, evidence is limited regarding the impacts of LAN exposure on human inflammation.

OBJECTIVES

To examine the association between real-ambient bedroom LAN exposure with systemic inflammation and circadian rhythm of inflammatory markers.

METHODS

Using data from a prospective cohort study of Chinese young adults. At baseline, bedroom LAN exposure was measured with a portable illuminance meter; fasting blood sample for high-sensitivity C-reactive protein (hs-CRP) assay was collected. At 3-year follow-up, 20 healthy young adults (10 LANavg < 5 lx, 10 LANavg ≥ 5 lx) were recruited from the same cohort; time-series venous blood samples were sampled every 4 h over a 24 h-cycle for the detection of 8 inflammatory markers. Circadian rhythm of inflammatory markers was assessed using cosinor analysis.

RESULTS

At baseline, the average age of the 276 participants was 18.7 years, and 33.3 % were male. Higher levels of bedroom LAN exposure were significantly associated with increased hs-CRP levels. The association between bedroom LAN exposure and systemic inflammation was only significant in the inactive group (MVPA < 2 h/d) but not in the physically active group (MVPA ≥ 2 h/d). In addition, exposure to higher levels of nighttime light (LANavg ≥ 5 lx) disrupted circadian rhythms (including rhythmic expression, circadian amplitude and circadian phase) of some inflammatory cytokines and inflammatory balance indicators.

CONCLUSION

Exposure to bedroom nighttime light increases systemic inflammation and disrupts circadian rhythm of inflammatory markers. Keep bedroom darkness at night may represent important strategies for the prevention of chronic inflammation. Additionally, for people living a community with higher nighttime light pollution, regular physical activity may be a viable option to counteract the negative impacts of LAN exposure on chronic inflammation.

Exposure to real-ambient bedroom light at night delayed circadian rhythm in healthy Chinese young adults: A cross-sectional study

BACKGROUND

Light at night (LAN) have attracted increased research attention on account of its widespread health hazards. However, the underlying mechanism remains unknown. The objective of this study was to investigate the effects of real-ambient bedroom LAN exposure on circadian rhythm among young adults and potential sex differences.

METHODS

Bedroom LAN exposure was measured at 60-s intervals for 2 consecutive days using a portable illuminance meter. Circadian phase was determined by the dim light melatonin onset (DLMO) time in 7 time-series saliva samples.

RESULTS

The mean age of the 142 participants was 20.7 ± 0.8 years, and 59.9% were women. The average DLMO time was 21:00 ± 1:11 h, with men (21:19 ± 1:12 h) later than women (20:48 ± 1:07 h). Higher level of LAN intensity (LANavg ≥ 3lx vs. LANavg < 3lx) was associated with an 81.0-min later in DLMO time (95% CI: 0.99, 1.72), and longer duration of nighttime light intensity ≥ 5lx (LAN5; LAN5 ≥ 45 min vs. LAN5 < 45 min) was associated with a 51.6-min later in DLMO time (95% CI: 0.46, 1.26). In addition, the delayed effect of LAN exposure on circadian phase was more pronounced in men than in women (all P-values <0.05).

CONCLUSIONS

Overall, bedroom LAN exposure was significantly associated with delayed circadian rhythm. Additionally, the delayed effect is more significant in men. Keeping bedroom dark at night may be a practicable option to prevent circadian disruption and associated health implications. Future studies with more advanced light measurement instrument and consensus methodology for DLMO assessment are warranted.

Spatiotemporal Dynamics of COVID-19 Pandemic City Lockdown: Insights From Nighttime Light Remote Sensing

The global COVID-19 outbreak severely hampered the growth of the global economy, prompting the implementation of the strictest prevention policies in China. Establishing a significant relationship between changes in nighttime light and COVID-19 lockdowns from a geospatial perspective is essential. In light of nighttime light remote sensing, we evaluated the spatiotemporal dynamic effects of COVID-19 city lockdowns on human activity intensity in the Zhengzhou region. Prior to the COVID-19 outbreak, nighttime light in the Zhengzhou region maintained a significant growth trend, even under regular control measures. However, following the October 2022 COVID-19 lockdown, nighttime light experienced a substantial decrease. In the central area of Zhengzhou, nighttime light decreased by at least 18% compared to pre-lockdown levels, while in the sub-center, the decrease was around 14%. The areas where nighttime light decreased the most in the central region were primarily within a 15 km radius, while in the sub-center, the decrease was concentrated within a 5 km radius. These changes in both statistical data and nighttime light underscored the significant impact of the COVID-19 lockdown on economic activities in the Zhengzhou region.

Outdoor artificial light at night exposure and gestational diabetes mellitus: a case-control study

Objective

This study aims to explore the association between outdoor artificial light at night (ALAN) exposure and gestational diabetes mellitus (GDM).

Methods

This study is a retrospective case-control study. According with quantiles, ALAN has been classified into three categories (Q1-Q3). GDM was diagnosed through oral glucose tolerance tests. Conditional logistic regression models were used to evaluate the association between ALAN exposure and GDM risk. The odds ratio (OR) with 95% confidence interval (CI) was used to assess the association. Restricted cubic spline analysis (RCS) was utilized to investigate the no liner association between ALAN and GDM.

Results

A total of 5,720 participants were included, comprising 1,430 individuals with GDM and 4,290 matched controls. Pregnant women exposed to higher levels of ALAN during the first trimester exhibited an elevated risk of GDM compared to those with lower exposure levels (Q2 OR = 1.39, 95% CI 1.20-1.63, p < 0.001); (Q3 OR = 1.70, 95% CI 1.44-2.00, p < 0.001). Similarly, elevated ALAN exposure during the second trimester also conferred an increased risk of GDM (second trimester: Q2 OR = 1.70, 95% CI 1.45-1.98, p < 0.001; Q3 OR = 2.08, 95% CI 1.77-2.44, p < 0.001). RCS showed a nonlinear association between ALAN exposure and GDM risk in second trimester pregnancy, with a threshold value of 4.235.

Conclusion

Outdoor ALAN exposure during pregnancy is associated with an increased risk of GDM.

Outdoor Light at Night, Air Pollution, and Risk of Cerebrovascular Disease: A Cohort Study in China

BACKGROUND

We sought to explore the associations of outdoor light at night (LAN) and air pollution with the risk of cerebrovascular disease (CeVD).

METHODS

We included a total of 28 302 participants enrolled in Ningbo, China from 2015 to 2018. Outdoor LAN and air pollution were assessed by Satellite-derived images and land-use regression models. CeVD cases were confirmed by medical records and death certificates and further subdivided into ischemic and hemorrhagic stroke. Cox proportional hazard models were used to estimate hazard ratios and 95% CIs.

RESULTS

A total of 1278 CeVD cases (including 777 ischemic and 133 hemorrhagic stroke cases) were identified during 127 877 person-years of follow-up. In the single-exposure models, the hazard ratios for CeVD were 1.17 (95% CI, 1.06-1.29) for outdoor LAN, 1.25 (1.12-1.39) for particulate matter with an aerodynamic diameter ≤2.5 µm, 1.14 (1.06-1.22) for particulate matter with aerodynamic diameter ≤10 μm, and 1.21 (1.06-1.38) for NO2 in every interquartile range increase. The results were similar for ischemic stroke, whereas no association was observed for hemorrhagic stroke. In the multiple-exposure models, the associations of outdoor LAN and PM with CeVD persisted but not for ischemic stroke. Furthermore, no interaction was observed between outdoor LAN and air pollution.

CONCLUSIONS

Levels of exposure to outdoor LAN and air pollution were positively associated with the risk of CeVD. Furthermore, the detrimental effects of outdoor LAN and air pollution might be mutually independent.

The relationship between nighttime exercise and problematic smartphone use before sleep and associated health issues: a cross-sectional study

OBJECTIVE

Physical exercise has the potential to mitigate addictive behaviors and relevant health issues. However, the nighttime exercise has not been studied regarding this research topic. This study aims to explore the association between nocturnal physical exercise and problematic smartphone use before sleep, as well as related health issues.

METHODS

To explore the association between nighttime physical exercise and problematic smartphone use before sleep as well as related health issues, we conducted a cross-sectional survey among 1,334 college students. Their daily exercise behaviors (including timeframe, rationale, frequency, and duration), smartphone use before sleep, sleep quality, smartphone addiction, anxiety, and depression were measured by questionnaires. The associations were assessed using generalized linear models.

RESULTS

Our findings indicate that nearly 70% of participants chose to perform exercise at nighttime. Among these individuals who exercised at nighttime, the frequency and duration of nighttime exercise were significantly associated with decreased probabilities of smartphone use before sleep. Additionally, the frequency and duration of nighttime exercise were associated with lower levels of smartphone addiction and anxiety disorders.

CONCLUSION

Nighttime Exercise behaviors can effectively reduce sleep delays caused by problematic smartphone use before bedtime. These findings contribute to understanding the potential effects of nighttime exercise on problematic smartphone use and relevant health issues. Future research should employ more precise methodologies to examine these associations.

Association between exposure to outdoor artificial light at night and the risk of preterm birth

Background

This study aimed to investigate the association between outdoor artificial light at night (ALAN) exposure during pregnancy and the risk of preterm birth (PTB).

Methods

A retrospective case-control study was conducted, and data were collected from pregnant women residing in Beijing, China. The level of ALAN exposure during pregnancy was estimated using remote sensing satellite data. Propensity score matching was utilized to match the control group. Logistic and multivariate linear regression were used to analyze the association between ALAN and the risk of PTB. The odds ratio (OR) and partial regression coefficient (β) with 95% confidence interval (CI) were utilized to assess the association.

Results

A total of 2,850 pregnant women were enrolled in this study. ALAN (nW/cm2/sr) exposure was higher in the PTB group than in the control group during first trimester (mean ± standard deviation: 25.30 ± 17.91 vs. 17.56 ± 14.74, p < 0.001) and second trimester (27.07 ± 18.10 vs. 21.93 ± 16.08, p < 0.001). A negative association was found between ALAN exposure and gestation day in the first (β = -0.151, 95%CI: -0.217 to -0.085, p < 0.001) and second trimesters (β = -0.077, 95%CI: -0.139 to -0.015, p = 0.015). ALAN was identified as a risk factor for PTB during the first trimester (OR = 1.032, 95%CI: 1.025-1.040, p < 0.001) and the second trimester (OR = 1.018, 95%CI: 1.011-1.025, p < 0.001), while no significant association was observed in the third trimester.

Conclusion

Our study suggesting that exposure to outdoor ALAN, especially during first and second trimester, was associated with the risk of PTB. These findings highlight the potential impact of ALAN on pregnancy health and offer new insights into the risk of PTB.

Daylight exposure and circadian clocks in broilers: part I-photoperiod effect on broiler behavior, skeletal health, and fear response

The aim of this study was to examine effects of various daylight exposure during the 24-h light-dark (L-D) cycle on growth performance, skeletal health, and welfare state in broilers. Environmental photoperiod and related circadian clock, the 24-h L-D cycle, are important factors in maintaining productive performance, pathophysiological homeostasis, and psychological reaction in humans and animals. Currently, various lighting programs as management tools for providing a satisfactory environmental condition have been used in commercial broiler production. Four hundred thirty-two 1-day-old Rose 308 broiler chicks were assigned to 24 pens (18 birds/pen). The pens were randomly assigned to 1 of 4 thermal and lighting control rooms, then the birds were exposed to (n = 6): 1) 12L, 2) 16L, 3) 18L, or 4) 20L at 15 d of age. Lighting program effects on bird body weight, behavioral patterns, bone health, and stress levels were evaluated from d 35 to d 45, respectively. The birds of 12L as well as 16L groups, reared under short photoperiods close to the natural 24-h L-D cycle, had improved production performance, leg bone health, and suppressed stress reaction compared to the birds of both 18L and 20L groups. Especially, 12L birds had heavier final body weight and averaged daily weight gain (P < 0.05), higher BMD and BMC with longer and wider femur (P < 0.05), lower H/L ratio (P < 0.05), and more birds reached the observer during the touch test (P < 0.05) but spent shorter latency during the tonic immobility test (P < 0.05). Taken together, the data suggest that supplying 12 h as well as 16L of daily light improves performance and health while decreasing stress levels in broilers, making it a potentially suitable approach for broiler production.

Inappropriate nighttime light reduces living comfort

Living comfort is an important aspect of human well-being and a critical index of sustainable environments. Many environmental factors are associated with living comfort. Nighttime light (NTL) is remote sensing data that is widely used to reflect development level and economic status, and it also represents the lighting intensity in living environments. However, the relationship between NTL and living comfort is poorly understood. Here, we employ linear regression and a random forest model to investigate the direct impact of NTL on living comfort. Our results show that increased NTL is negatively associated with living comfort, but this relationship may be obscured by other factors, such as infrastructure. According to the nonlinear relationship, when the NTL is approximately 10 nW/cm2∙sr, there is a peak in living comfort. Hence, ensuring a reasonable level of lighting is a key to promoting sustainable development. Our research offers crucial insights that can aid in developing sustainable development policies to enhance livability.