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Helbich, M., Browning, M. H. E. M., & Huss, A. (2020). Outdoor light at night, air pollution and depressive symptoms: A cross-sectional study in the Netherlands. Science of The Total Environment, in press, 140914.
Abstract: Background
Artificial light at night (ALAN) may be an anthropogenic stressor for mental health disturbing humans' natural day–night cycle. However, the few existing studies used satellite-based measures of radiances for outdoor ALAN exposure assessments, which were possibly confounded by traffic-related air pollutants.
Objective
To assess 1) whether living in areas with increased exposure to outdoor ALAN is associated with depressive symptoms; and 2) to assess the potential confounding effects of air pollution.
Methods
We used cross-sectional data from people (N = 10,482) aged 18–65 years in the Netherlands. Depressive symptoms were assessed with the Patient Health Questionnaire (PHQ–9). Satellite-measured annual ALAN were taken from the Visible Infrared Imaging Radiometer Suite. ALAN exposures were assessed at people's home address within 100 and 600 m buffers. We used generalized (geo)additive models to quantify associations between PHQ–9 scores and quintiles of ALAN adjusting for several potential confounders including PM2.5 and NO2.
Findings
Unadjusted estimates for the 100 m buffers showed that people in the 2nd to 5th ALAN quintile showed significantly higher PHQ–9 scores than those in the lowest ALAN quintile (βQ2 = 0.503 [95% confidence interval, 0.207–0.798], βQ3 = 0.587 [0.291–0.884], βQ4 = 0.921 [0.623–1.218], βQ5 = 1.322 [1.023–1.620]). ALAN risk estimates adjusted for individual and area-level confounders (i.e., PM2.5, urbanicity, noise, land-use diversity, greenness, deprivation, and social fragmentation) were attenuated but remained significant for the 100 m buffer (βQ2 = 0.420 [0.125–0.715], βQ3 = 0.383 [0.071–0.696], βQ4 = 0.513 [0.177–0.850], βQ5 = 0.541 [0.141–0.941]). When adjusting for NO2 per 100 m buffers, the air pollutant was associated with PHQ–9 scores, but ALAN did not display an exposure-response relationship. ALAN associations were insignificance for 600 m buffers.
Interpretation
Accounting for NO2 exposure suggested that air pollution rather than outdoor ALAN correlated with depressive symptoms. Future evaluations of health effects from ALAN should consider potential confounding by traffic-related exposures (i.e., NO2).
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Rabstein, S., Burek, K., Lehnert, M., Beine, A., Vetter, C., Harth, V., et al. (2019). Differences in twenty-four-hour profiles of blue-light exposure between day and night shifts in female medical staff. Science of The Total Environment, 653, 1025–1033.
Abstract: Light is the strongest zeitgeber currently known for the synchronization of the human circadian timing system. Especially shift workers are exposed to altered daily light profiles. Our objective is the characterization of differences in blue-light exposures between day and night shift taking into consideration modifying factors such as chronotype. We describe 24-hour blue-light profiles as measured with ambient light data loggers (LightWatcher) during up to three consecutive days with either day or night shifts in 100 female hospital staff including 511 observations. Linear mixed models were applied to analyze light profiles and to select time-windows for the analysis of associations between shift work, individual factors, and log mean light exposures as well as the duration of darkness per day. Blue-light profiles reflected different daily activities and were mainly influenced by work time. Except for evening (7–9 p.m.), all time windows showed large differences in blue-light exposures between day and night shifts. Night work reduced the duration of darkness per day by almost 4 h (beta = −3:48 hh:mm, 95% CI (−4:27; −3.09)). Late chronotypes had higher light exposures in the morning and evening compared to women with intermediate chronotype (e.g. morning beta = 0.50 log(mW/m2/nm), 95% CI (0.08; 0.93)). Women with children had slightly higher light exposures in the afternoon than women without children (beta = 0.48, 95% CI (−0.10; 1,06)). Time windows for the description of light should be chosen carefully with regard to timing of shifts. Our results are helpful for future studies to capture relevant light exposure differences and potential collinearities with individual factors. Improvement of well-being of shift workers with altered light profiles may therefore require consideration of both – light at the workplace and outside working hours.
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Xiao, H., Cai, H., & Li, X. (2020). Non-visual effects of indoor light environment on humans: A review. Physiology & Behavior, in press, 113195.
Abstract: As a result of the desire to improve living standards, increasing attention is paid to creating a comfortable and healthy lighting environment that contributes to human health and well-being. It is crucial to understand the effects of environmental lighting regulation on humans’ physical responses and mental activities. In this review, we focus on the scientific research on light-induced non-visual effects on humans, providing a systematic review of how the quantity of light, spectral changes, time of day, and duration have effects on the circadian rhythm, alertness, and mood based on eligible literature. The key findings are as follows: (1) The increase of illuminance and correlated colour temperature (CCT) at night were both positively associated with melatonin suppression, thus affecting the circadian rhythm. Meanwhile, a high CCT is conducive to the stimulation of positive mood. (2) Blue light and high CCT light at night induced delayed phase shift, and the objective alertness was reduced under the condition of lack of blue components. (3) High illuminance was positively correlated with subjective alertness during daytime, and increased the positive mood in the morning and decreased it in the afternoon. These findings serve as an important reference for stakeholders to optimise lighting in constructed environments to improve health and well-being considering the non-visual effects above and beyond visual performance.
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Liu, J., Ghastine, L., Um, P., Rovit, E., & Wu, T. (2020). Environmental Exposures and Sleep Outcomes: a review of evidence, potential mechanisms, and implications. Environmental Research, in press.
Abstract: Environmental exposures and poor sleep outcomes are known to have consequential effects on human health. This integrative review first seeks to present and synthesize existing literature investigating the relationship between exposure to various environmental factors and sleep health. We then present potential mechanisms of action as well as implications for policy and future research for each environmental exposure. Broadly, although studies are still emerging, empirical evidence has begun to show a positive association between adverse effects of heavy metal, noise pollution, light pollution, second-hand smoke, and air pollution exposures and various sleep problems. Specifically, these negative sleep outcomes range from subjective sleep manifestations, such as general sleep quality, sleep duration, daytime dysfunction, and daytime sleepiness, as well as objective sleep measures, including difficulties with sleep onset and maintenance, sleep stage or circadian rhythm interference, sleep arousal, REM activity, and sleep disordered breathing. However, the association between light exposure and sleep is less clear. Potential toxicological mechanisms are thought to include the direct effect of various environmental toxicants on the nervous, respiratory, and cardiovascular systems, oxidative stress, and inflammation. Nevertheless, future research is required to tease out the exact pathways of action to explain the associations between each environmental factor and sleep, to inform possible therapies to negate the detrimental effects, and to increase efforts in decreasing exposure to these harmful environmental factors to improve health.
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Lai, K. Y., Sarkar, C., Ni, M. Y., Gallacher, J., & Webster, C. (2020). Exposure to light at night (LAN) and risk of obesity: a systematic review and meta-analysis of observational studies. Environmental Research, in press, in press.
Abstract: Background
There is emerging evidence of the association between light at night (LAN) exposure and weight gain.
Objective
We aim to conduct a systematic review and meta-analysis of observational studies on the association between LAN exposure and risk of obesity in human subjects.
Methods
Peer-reviewed observational studies were systematically searched from MEDLINE (EBSCO), Academic Search Complete (EBSCO), CINAHL Plus (EBSCO) and PubMed up to 24 December 2019. Random-effects models were developed to estimate the associations between LAN exposure and weight-related outcomes of overweight and obesity as measured by body mass index (BMI), waist circumference, waist-hip-ratio and waist-to-height-ratio. The I2 statistic was used to assess the degree of heterogeneity across studies. The National Toxicology Program’s Office of Health Assessment and Translation (OHAT) risk of bias rating tool and the Grading of Recommendations Assessment, Development and Evaluation (GRADE) guideline were respectively employed to assess the risk of bias and to appraise the quality of the generated evidence.
Results
A total of 12 studies (three with longitudinal and nine of cross-sectional design) published between 2003-2019 were included for systematic review, while seven of them fulfilling the inclusion/exclusion criteria were included in the meta-analysis. A higher LAN exposure was significantly associated with 13% higher odds of overweight (BMI≥25 kg/m2) (Summary Odds Ratio; SOR: 1.13, 95% CI: 1.10-1.16) with low heterogeneity (I2 = 27.27%), and 22% higher odds of obesity (BMI≥30 kg/m2) (SOR: 1.22, 95% CI: 1.07-1.38) with substantial heterogeneity (I2 = 85.96%). Stratifying analyses by the levels of measurement of LAN exposures (macro-, meso- and micro-levels) and time of LAN measurement (including before and while sleeping) consistently produced robust estimates, with higher exposure to LAN being positively associated with poorer weight outcomes. Assessment of risk of bias identified substantial detection bias for exposure, with over half of the pooled studies employing subjective LAN measures. The overall evidence of the association between LAN exposure and risk of obesity was rated as ‘moderate’ as per the GRADE guideline.
Conclusions
Exposure to LAN was reported to be a significant risk factor for overweight and obesity. Prospectively designed future studies with objectively measured multi-level LAN exposures and weight outcomes are required.
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