Advances in research on relationship between indoor artificial light at night and human health / 环境与职业医学

With the acceleration of global urbanization, the intensity and coverage of artificial light at night (ALAN) are increasing, and its service duration is obviously prolonged. ALAN exposure is not only related to the occurrence and development of cardiovascular, metabolic, sleep, myopia, and mental diseases, but also may induce cancer. Previous studies have focused on the health effects of outdoor ALAN, but people spend more than 80% of their lives indoors, hence it is of great significance to understand the relationship between indoor ALAN and population health to create a healthy indoor environment and protect the health of the population.

Association of outdoor artificial light at night exposure with overweight and obesity among children and adolescents aged 9 to 18 years in China / 北京大学学报(医学版)

OBJECTIVE@#To analyze the association between outdoor artificial light-at-night (ALAN) exposure and overweight and obesity among children and adolescents aged 9 to 18 years in China.@*METHODS@#Using follow-up data of 5 540 children and adolescents aged 9 to 18 years conducted from November 2019 to November 2020 in eight provinces of China, latitude and longitude were determined based on school addresses, and the mean monthly average nighttime irradiance at the location of 116 schools was extracted by the nearest neighbor method to obtain the mean outdoor ALAN exposure [unit: nW/(cm2·sr)] for each school. Four indicators of overweight and obesity outcomes were included: Baseline overweight and obesity, persistent overweight and obesity, overweight and obesity progression and overweight and obesity incidence. Mixed effects Logistic regression was used to explore the association between ALAN exposure levels (divided into quintiles Q1-Q5) and baseline overweight and obesity, persistent overweight and obesity, overweight and obesity progression and overweight and obesity incidence. In addition, a natural cubic spline function was used to explore the exposure response association between ALAN exposure (a continuous variable) and the outcomes.@*RESULTS@#The prevalence of baseline overweight and obesity, persistent overweight and obesity, overweight and obesity progression and overweight and obesity incidence among the children and adolescents in this study were 21.6%, 16.3%, 2.9% and 12.8%, respectively. The OR value for the association between ALAN exposure and baseline overweight and obesity was statistically significant when ALAN exposure levels reached Q4 or Q5, 1.90 (95%CI: 1.26-2.86) and 1.77 (95%CI: 1.11-2.83), respectively, compared with the children and adolescents in the Q1 group of ALAN exposure. Similar to the results for baseline overweight and obesity, the OR values for the association with persistent overweight and obesity were 1.89 (95%CI: 1.20-2.99) and 1.82 (95%CI: 1.08-3.06) when ALAN exposure levels reached Q4 or Q5, respectively, but none of the OR values for the association between ALAN and overweight and obesity progression and overweight and obesity incidence were statistically significant. Fitting a natural cubic spline function showed a non-linear trend between ALAN exposure and persistent overweight and obesity.@*CONCLUSION@#There is a positive association between ALAN exposure and overweight and obesity in children and adolescents, and the promotion of overweight obesity in children and adolescents by ALAN tends to have a cumulative effect rather than an immediate effect. In the future, while focusing on the common risk factors for overweight and obesity in children and adolescents, there is a need to improve the overweight and obesity-causing nighttime light exposure environment.

Review on health effects of indoor and outdoor artificial light at night / 环境与职业医学

A growing number of urban dwellers are being exposed to excessively bright artificial night light induced by the development of high-intensity, high-density cities around the world. The adverse health effects of artificial light at night (ALAN) are increasingly becoming a global public health issue. Investigating the effects of built environment, especially ALAN, on public health has progressively developed into a cross-disciplinary research hotspot since the World Health Organization launched the Healthy Cities Project. Numerous studies found the links between ALAN and multiple negative health outcomes. However, to date, no review has summarized the health impacts of ALAN in China. This article systematically outlined the progress of research on the health effects of indoor and outdoor ALAN, including sleep disorders, obesity, cancers, cardiovascular diseases, metabolic diseases, cognitive function, and mental health. We pointed out the limitations of current research such as errors in exposure assessment, lack of research in developing countries, weak causal argument, and difficulty in controlling confounding factors. Future research should improve study design, conduct quantitative studies, and explore potential mechanisms, so as to provide scientific evidence for improving urban lighting planning and urban architectural design.

Effect of light at night on liver metabolism in miceby untargeted metabolomics / 预防医学

Objective@#To observe the changes of liver metabolism in mice exposed to artificial light at night. @*Methods@#Healthy male C57BL/6J mice were randomly divided into the light at night group and the control group, with 8 mice in each group. The daily light/dark cycle was 12/12 hours in the control group, and 24/0 hours in the light at night group for 10 consecutive days. The hepatic metabolite profiles of the two groups of mice were detected by high performance liquid chromatography tandem mass spectrometry. The modelling was assessed by combining principal component analysis (PCA) and orthogonal partial least squares-discriminant analysis ( OPLS-DA ) , The changes of metabolites in the two groups were compared through KEGG database.@*Results@#Compared with the control group, 9 different metabolites were detected in the light at night group, among which the down-regulated metabolites were glycine-betaine, glutathione, tyrosine, betaine, lysine, hypoxanthine, histidine and methionine, and the up-regulated ones were mannose-6-phosphate. The weight analysis of the metabolic pathways showed that the major influences on liver of light at night group were phenylalanine-tyrosine-tryptophan metabolism, tyrosine metabolism, fructose and mannose metabolism, cysteine and methionine metabolism and histidine metabolism. @*Conclusion@#The metabolism of various amino acids and sugars in light at night mice is disturbed,and the key differential metabolites are tyrosine, methionine, histidine and mannose-6-phosphate.

Dose-response relationship between light at night and nonalcoholic fatty liver in steel workers / 中华疾病控制杂志

Objective To explore the relationship between light at night (LAN) and nonalcoholic fatty liver (NAFLD) in steel workers. Methods Relevant information was collected through questionnaires, physical examinations and blood biochemical analysis. Using restricted cubic spline (RCS) and mutiple Logistic regression model to explore the relationship between LAN and NAFLD based on a cross-sectional study. Results The prevalence of NAFLD was 33.8% (2 594 / 7 664) in steel workers. After adjusting for age, sex, marriage, educational level, smoking, drinking, body mass index, luminous intensity in life, liver enzyme metabolism, blood lipid level, physical activity, diet, sleep duration, shift work, high temperature, noise, dust, and carbon monoxide exposure, the RCS model showed a nonlinear dose-response relationship between LAN and NAFLD ( 2=71.59, P<0.001 for overall association test and 2=16.92, P<0.001 for nonlinear test); Multivariate Logistic regression model showed that after adjusting for all confounding factors, when the LAN in the 1 178 d ~ 2 017 d and 2 017 d ~ group, the prevalence of NAFLD increased by 21.7% (OR=1.217, 95% CI: 1.027-1.441) and 47.9% (OR=1.479, 95% CI: 1.240-1.763), respectively, when compared with the group LAN<1 178 d. Conclusion There is a nonlinear dose-response relationship between LAN and NAFLD in steel works.

Influence of Circadian Disruption Associated With Artificial Light at Night on Micturition Patterns in Shift Workers / 대한배뇨장애요실금학회지

Shift workers often experience problems associated with circadian disruption associated with artificial light at night and nocturia is commonly noted in night-shift workers. Nocturia associated with circadian disruption is due to increased urine production of the kidney and decreased storage function of the bladder. A recent discovery of peripheral clock genes in the bladder and their role in contractile property of the bladder support that micturition is closely related to the circadian rhythm. Moreover, there are clinical studies showed that shift workers more often experienced nocturia due to circadian disruption. However, comparing with other health problems, concerns on nocturia and voiding dysfunction associated with circadian disruption are insufficient. Therefore, further studies about voiding dysfunction associated with the circadian disruption in shift workers are necessary.

Impact of Exposure to Dim Light at Night on Sleep in Female and Comparison with Male Subjects

OBJECTIVE: Light pollution has become a social and health issue. We performed an experimental study to investigate impact of dim light at night (dLAN) on sleep in female subjects, with measurement of salivary melatonin. METHODS: The 25 female subjects (Group A: 12; Group B: 13 subjects) underwent a nocturnal polysomnography (NPSG) session with no light (Night 1) followed by an NPSG session randomly assigned to two conditions (Group A: 5; Group B: 10 lux) during a whole night of sleep (Night 2). Salivary melatonin was measured before and after sleep on each night. For further investigation, the female and male subjects of our previous study were collected (48 subjects), and differences according to gender were compared. RESULTS: dLAN during sleep was significantly associated with decreased total sleep time (TST; F=4.818, p=0.039), sleep efficiency (SE; F=5.072, p=0.034), and Stage R latency (F=4.664, p=0.041) for female subjects, and decreased TST (F=14.971, p<0.001) and SE (F=7.687, p=0.008), and increased wake time after sleep onset (F=6.322, p=0.015) and Stage R (F=5.031, p=0.03), with a night-group interaction (F=4.579, p=0.038) for total sample. However, no significant melatonin changes. There was no significant gender difference of the impact of dLAN on sleep, showing the negative changes in the amount and quality of sleep and the increase in rapid eye movement (REM) sleep in the both gender group under 10 lux condition. CONCLUSION: We found a negative impact of exposure to dLAN on sleep in female as well as in merged subjects. REM sleep showed a pronounced increase under 10 lux than under 5 lux in merged subjects, suggesting the possibility of subtle influences of dLAN on REM sleep.

Impact of Dim Artificial Light at Night (dALAN) Exposure during Sleep on Human Fatigue / 수면정신생리

OBJECTIVES: Exposure to light at night has become pervasive in modern society. The impact of dim artificial light at night (dALAN) exposure on sleep and fatigue is not well recognized. We aim to study the impact of dALAN exposure during sleep on human fatigue. METHODS: 30 healthy young male volunteers from 21 to 29 years old were enrolled in the study. They were randomly divided into two groups depending on light intensity (Group A : 5 lux and Group B : 10 lux). Data were gathered from each participant after each night with no light (Night 1) followed by the next night (Night 2) with two different dim light conditions (5 or 10 lux) by means of self-reported fatigue scale. RESULTS: Exposure to dALAN during sleep was significantly associated with increased overall fatigue (F = 19.556, p < 0.001) and ocular discomfort (F = 5.671, p = 0.028). CONCLUSION: We found that dALAN during sleep likely affects human fatigue in some aspects. These findings indicate that dALAN during sleep exerts a negative effect on human fatigue.