Impact of Dim Light at Night on Urinary 6-Sulphatoxymelatonin Concentrations and Sleep in Healthy Humans

Use of Light Protection Equipment at Night Reduces Time Until Discharge From the Neonatal Intensive Care Unit: A Randomized Interventional Study

Newborn infants' circadian systems are not completely developed and rely on external temporal cues for synchronizing their biological rhythms to the environment. In neonatal intensive care units (NICUs), lighting is usually continuous or irregular and infants are exposed to artificial light at night, which can have negative health consequences. Therefore, the aim of this study was to evaluate the impact of the use of individual light protection equipment at night on the development and growth of preterm neonates. Infants born at less than 37 gestational weeks who no longer needed constant intensive care were admitted into a newborn nursery and randomized to either use eye masks at night (intervention, n = 21) or not (control, n = 20). Infants who used eye protection at night were discharged earlier than those in the control group (8 [5] vs 12 [3.75] days; p < 0.05). A greater variation within the day in heart rate was observed in the intervention group, with lower values of beats per minute at 1400 and 2000 h. There was no significant difference in weight gain between groups. In view of our results and of previous findings present in the literature, we suggest that combining a darkened environment at night with individual light protection devices creates better conditions for the development of preterm infants in the NICU. In addition, eye masks are an affordable and simple-to-use tool that can reduce hospitalization costs by decreasing the number of days spent in the NICU.

Artificial light at night, MRI-based measures of brain iron deposition and incidence of multiple mental disorders

BACKGROUND

Epidemiologic evidence on whether iron accumulation in brain modified the association between artificial light at night (ALAN) and incident mental disorders is lacking. The authors aims to investigate modification of brain iron deposition on the associations of ALAN with multiple mental disorders in the middle-aged and older adults.

METHODS

This prospective study used data from the UK Biobank. ALAN was drawn from satellite datasets. Susceptibility-weighted magnetic resonance imaging was used to ascertain iron content of each brain region. T2* signal loss was used as indices of iron deposition. The main outcomes are impacts of ALAN exposure on onset of wide spectrum of physician-diagnosed mental disorders, which was estimated by time-varying Cox proportional hazard model. The authors further conducted stratified analyses by levels of iron brain deposition to examine the potential modifying effects.

RESULTS

Among 298,283 participants followed for a median of 10.91 years, higher ALAN exposure was associated with increased risk of mental disorders. An IQR (11.37 nW/cm2/sr) increase in annual levels of ALAN was associated with an HR of 1.050 (95 % CI: 1.034,1.066) for any mental disorder, 1.076 (95 % CI: 1.053,1.099) for substance use disorder, and 1.036 (95 % CI: 1.004,1.069) for depression disorder in fully adjusted models. The exposure-response curves showed steeper trends at lower ALAN levels and a plateau at higher exposures. The associations were stronger in participants with high iron deposition in left hippocampus, left accumbens and left pallidum.

CONCLUSIONS

ALAN was associated with multiple mental disorders in the middle-aged and older adults, and the findings indicated stricter standards of ALAN is needed and targeted preventive measures are warranted, especially with high brain iron deposition.

Disturbances of Hormonal Circadian Rhythms by Light Pollution

The circadian rhythms evolved to anticipate and cope with cyclic changes in environmental conditions. This adaptive function is currently compromised by increasing levels of artificial light at night (ALAN), which can represent a risk for the development of diseases of civilisation. The causal links are not completely understood, and this featured review focuses on the chronodisruption of the neuroendocrine control of physiology and behaviour by dim ALAN. The published data indicate that low levels of ALAN (2-5 lux) can attenuate the molecular mechanisms generating circadian rhythms in the central oscillator, eliminate the rhythmic changes in dominant hormonal signals, such as melatonin, testosterone and vasopressin, and interfere with the circadian rhythm of the dominant glucocorticoid corticosterone in rodents. These changes are associated with a disturbed daily pattern of metabolic changes and behavioural rhythms in activity and food and water intake. The increasing levels of ALAN require the identification of the pathways mediating possible negative consequences on health to design effective mitigation strategies to eliminate or minimise the effects of light pollution.

Light pollution as a factor in breast and prostate cancer

Light pollution is a global environmental issue that affects photosensitive organisms. For instance, several researchers have recognized melatonin suppression in humans as a direct cause of long-term exposure to high artificial light levels at night. Others have identified low melatonin levels as a risk factor for a higher prevalence of hormone-sensitive cancer. This paper analyzes the association between light pollution, estimated as the emission analysis of satellite worldwide nighttime light collections from 1999 to 2012, and 25,025 breast and 16,119 prostate cancer events from 2003 to 2012. Both types of cancer increased during the study period, but light pollution increased in urban and peri-urban areas and decreased in rural areas. Cumulative light pollution during 5 years showed a positive association with breast cancer but not with prostate cancer. The association between light pollution and breast cancer persisted when adjusted to age-standardized rates with a mean increase of 10.9 events per 100,000 population-year (95% confidence interval 7.0 to 14.8). We conclude that exposure to elevated light pollution levels could be a risk factor for breast cancer in Slovakia. This work can interest researchers who study relationships between atmospheric pollutants and the growing cancer epidemic. The results and the methodology can be extrapolated to any country in the world if data is available.

The Exposome and Immune Health in Times of the COVID-19 Pandemic

Growing evidence supports the importance of lifestyle and environmental exposures-collectively referred to as the 'exposome'-for ensuring immune health. In this narrative review, we summarize and discuss the effects of the different exposome components (physical activity, body weight management, diet, sun exposure, stress, sleep and circadian rhythms, pollution, smoking, and gut microbiome) on immune function and inflammation, particularly in the context of the current coronavirus disease 2019 (COVID-19) pandemic. We highlight the potential role of 'exposome improvements' in the prevention-or amelioration, once established-of this disease as well as their effect on the response to vaccination. In light of the existing evidence, the promotion of a healthy exposome should be a cornerstone in the prevention and management of the COVID-19 pandemic and other eventual pandemics.

Sleep Characteristics According to Gender and Age Measured by Wrist Actigraphy

The sleep/wake rhythm is one of the most important biological rhythms. Quality and duration of sleep change during lifetime. The aim of our study was to determine differences in sleep efficiency, movement, and fragmentation during sleep period between genders and according to age. Sleep period was monitored by wrist actigraphy under home-based conditions. Seventy-four healthy participants-47 women and 27 men participated in the study. The participants were divided by age into groups younger than 40 years and 40 years and older. Women showed lower sleep fragmentation and mobility during sleep compared to men. Younger women showed a higher actual sleep and sleep efficiency compared to older women and younger men. Younger men compared to older men had a significantly lower actual sleep, lower sleep efficiency and significantly more sleep and wake bouts. Our results confirmed differences in sleep parameters between genders and according to age. The best sleep quality was detected in young women, but gender differences were not apparent in elderly participants, suggesting the impact of sex hormones on sleep.

Nail Melatonin Content: A Suitable Non-Invasive Marker of Melatonin Production

Melatonin plays multiple physiological roles in the human body. Evaluation of melatonin production by the determination of urinary 6-sulfatoxymelatonin in 24-h samples has important drawbacks which hinder the successful evaluation of melatonin production in large cohorts. Here, we evaluated the potential of nail analysis for estimating melatonin production. Firstly, mass spectrometry methodology for the determination of melatonin in nails was optimized and successfully validated. The method was found to be linear in the range 6.5-830 fg/mg with intraday and interday accuracy in the range 100-104 %, precision below 15 % and a LOD of 3.5 fg/mg. Secondly, nail melatonin concentrations from 84 volunteers (age 5-96) were determined. The expected correlation between melatonin and age was obtained (correlation coefficient -0.615; p < 0.001). Additionally, we showed that fingernails are preferable to toenails to determine nail melatonin content. Finally, fingernails collected for 180 days after melatonin administration (two volunteers, 1.9 mg/night during 5 days) were analyzed. Nail melatonin concentrations immediately rose after administration and went back to pre-administration values after ≈100 days in both volunteers. Our results suggest that melatonin determination in nails is a suitable non-invasive tool for the estimation of global melatonin production. Due to the easy collection and storage of nails, the long-term information obtained and the multiple functions of melatonin, nail melatonin content might complement dim light melatonin onset, which is commonly measured from plasma/saliva samples, paving the way for melatonin research.