Brighter nights and darker days predict higher mortality risk: A prospective analysis of personal light exposure in >88,000 individuals

Interactive effects of light at night and high fructose intake on the central circadian clock and endocrine outputs in rats

Light pollution is an increasing global environmental risk factor that contributes to the recent burden of metabolic diseases. The underlying mechanisms are not understood, but disruption of circadian control of physiological and behavioural processes may be involved. The negative consequences of chronodisruption can be augmented by co-exposure to high energy intake. Therefore, we investigated the individual and combined effects of artificial light at night (ALAN) and 10 % fructose in drinking water on the central clock in the suprachiasmatic nuclei (SCN) of the hypothalamus and circadian hormonal outputs in male rats. After 10 weeks of ALAN exposure and high fructose intake, the clockwork in the SCN was attenuated as indicated by eliminated day/night differences in the core clock gene Per1. Additionally, ALAN suppressed the daily variability and fructose induced upregulation of a gamma-aminobutyric acid-synthesising enzyme (GAD65), potentially affecting inhibitory neurotransmission in the SCN. ALAN and fructose additively inhibited plasma melatonin levels revealing excessive fructose intake as a chronodisruptive factor that can be potentiated by ALAN. In contrast to melatonin, daytime plasma testosterone concentrations were increased by high fructose and supressed by ALAN. Furthermore, high fructose intake elevated the plasma levels of two adipokines, leptin and adiponectin, but this response was absent specifically during the daytime in rats exposed to ALAN, indicating that ALAN reduced adipose tissue responsiveness. Our results document the complex consequences of ALAN and high fructose intake on endocrine control mechanisms that can have a long-term negative impact on metabolic health.

Biomarkers of aging: from molecules and surrogates to physiology and function

Many countries face an unprecedented challenge in aging demographics. This has led to an exponential growth in research on aging, which, coupled to a massive financial influx of funding in the private and public sectors, has resulted in seminal insights into the underpinnings of this biological process. However, critical validation in humans has been hampered by the limited translatability of results obtained in model organisms, additionally confined by the need for extremely time-consuming clinical studies in the ostensible absence of robust biomarkers that would allow monitoring in shorter time frames. In the future, molecular parameters might hold great promise in this regard. In contrast, biomarkers centered on function, resilience, and frailty are available at the present time, with proven predictive value for morbidity and mortality. In this review, the current knowledge of molecular and physiological aspects of human aging, potential antiaging strategies, and the basis, evidence, and potential application of physiological biomarkers in human aging are discussed.

Personal 24-hour light exposure pattern with obesity and adiposity-related parameters in school-aged children: A cross-sectional study based on compositional data analysis

The 24-h light exposure pattern is an essential feature of circadian rhythms and a potential contributor to body fat health. However, no previous studies have investigated 24-h light exposure patterns in relation to adiposity-related parameters in children. This cross-sectional study recruited school-aged children in Chuzhou, Anhui province, China. Personal 24-h light exposure was collected for 5 days and was divided into four measures: light at daytime (LAD)≥100 lx and <100 lx; light at night (LAN)≥1 lx and <1 lx. Adiposity-related parameters were measured via a body composition analyzer. The association of light exposure with adiposity-related parameters was analyzed using compositional data analysis (CoDA). This study included 831 children 8.53 ± 0.62 years, who were exposed to LAD≥100 lx for 490.1 ± 92.7 min and LAN≥1 lx for 311.2 ± 98.5 min. The proportion of time spent in LAD≥100 lx increasing by 1 % (14.4 min/day) was linked to a decline of 3.10 % in percentage of body fat (PBF). In contrast, prolonged exposure to LAN≥1 lx by 14.4 min/day was associated with an increase of 3.49 % in PBF (All P < 0.01). These associations were robust in boys after gender stratification. CoDA estimated that reducing the time of LAN≥1 lx had more influence in decreasing the odds of childhood overweight/obesity than increasing the time of LAD≥100 lx. Suboptimal 24-h light exposure patterns (brighter nights, darker days) play a threatening role in childhood overweight/obesity. Bright LAN replaced with darker LAN or bright LAD might help decrease the odds of childhood overweight/obesity.

Consensus Recommendations for Sustainable and Equitable Neonatology Staffing: A Delphi Approach

BACKGROUND AND OBJECTIVE

The specialty of neonatology faces significant and growing challenges related to patient safety, physician well-being, and workforce sustainability that highlight the necessity for innovative work models. Our objective was to develop consensus recommendations to improve neonatologist staffing practices in the United States.

METHODS

We used a modified Delphi process with 32 diverse subject-matter expert stakeholders to reach consensus. We derived 60 initial potential recommendations for improved staffing from the literature and our 2 previous studies of physician leaders. We defined consensus as 80% or higher agreement and strong consensus as 90% or higher agreement. We ultimately eliminated statements that achieved less than 80% consensus from the recommendations.

RESULTS

Fifty-one individual statements reached consensus and were grouped into 24 final recommendations to improve neonatology staffing. Topics of focus included clinical allocations (eg, clinic work is counted in hours/year), shift characteristics (eg, clinical work after 24 hours is minimized), allocation of nonclinical work (eg, nonclinical work is accounted for in full-time equivalent), and staffing flexibility (eg, options to restructure clinical work are provided for specific circumstances such as aging and pregnancy). Significant discussion on many statements focused on ensuring that recommendations were both feasible and not overly prescriptive for individual institutions.

CONCLUSIONS

We reached consensus on a set of neonatologist staffing recommendations that emphasize the critical issues related to patient safety and physician well-being. Future work will focus on advocating for widespread implementation of these recommendations and evaluating their effect on patient safety, physician well-being, and sustainability of the neonatal workforce.

Environmental pollution and cardiovascular health. Challenges and new perspectives

Environmental pollution is a key factor in cardiovascular disease (CVD) development. Several evidences support its impact at the pathophysiology of arteriosclerosis, highlighting the role of the "exposome", a concept that encompasses all environmental factors such as air pollution, water pollution, climate change and noise and light pollution. These factors are associated with an increased risk of ischemic heart disease (IHD), stroke, high blood pressure (HBP), heart failure (HF) and atrial fibrillation (AF). Currently, air pollution is the main environmental factor related to CVD. Components such as particulates matter (PM0.1, PM2.5, PM10), sulfur dioxide (SO2), nitrogen oxide and dioxide (NOx), carbon monoxide (CO) and ozone (O3) have a high capacity to penetrate the body and trigger both local and systemic inflammatory processes. These effects promote a proinflammatory, procoagulant state and an increase in oxidative stress. Similarly, aquatic pollution exposes the body to pollutants such as heavy metals, pesticides and microplastics, both through direct contact and via the food chain, thus contributing to the phenomena mentioned above. On the other hand, factors such as noise and light pollution, together with effects caused from climate change (extreme temperatures, wildfires, desertification, among others), have been closely linked to pathophysiological processes that favour the development and progression of atherosclerosis. These mechanisms include sympathetic nervous system (SNS) activation, stress hormones release such as cortisol and catecholamines, as well as chronodisruption. This review analyses the role of factors related to the exposome (air pollution, water pollution, noise and light pollution and phenomena associated with climate change) in atherosclerosis progression, as well as their involvement in the incidence, prevalence and prognosis of CVD. Physicians should promote awareness of environmental pollution impact on cardiovascular health, integrating the assessment of environmental factors into their clinical practice, advocating for sustainable policies to prevent diseases and protect present and future health.

Stuck in time: The slow march of circadian medicine and how to speed it up

While there is considerable enthusiasm for the translational and clinical applications of chronobiology, their actual implementation is not progressing as rapidly as might be expected. Here we discuss the possibility that this may relate to a combination of conceptual, methodological, evidentiary and training challenges. These are compounded by the remaining, profound cultural differences between basic and applied chronobiologists. We argue that all these issues can be overcome by cross-faculty teaching, time, patience and goodwill, together with a set of more formal actions, such as the establishment of a collaborative framework for evidence generation, the engagement of relevant stakeholders and public health campaigns based on already available evidence. We hope that chronobiology, and in particular the transformative power of circadian medicine, will change health outcomes, increase safety and improve quality of life for patients worldwide. Now is the time to bring "internal time" into medicine.

Physiological rhythms and metabolic regulation: Shining light on skeletal muscle

Metabolic regulation is essential for maintaining homeostasis in response to fluctuating dietary nutrient availability. In this review, we explore how metabolic health can be affected by the temporal alignment between daily behavioural patterns (e.g., eating, physical activity and sleep) and recurring cycles in underlying physiology (e.g., 'circadian' rhythms). Misalignment within and/or between these patterns and cycles can lead to metabolic dysregulation, increasing the risk of chronic disease states such as obesity, type 2 diabetes and cardiovascular disease. Conversely, metabolic health can be improved by strategically aligning certain behavioural patterns with endogenous rhythms in physiology. Dietary interventions based upon this reasoning are referred to as chrono-nutrition strategies. Skeletal muscle is an important tissue in relation to both whole-body metabolism and behaviour and plays a central role in how physiological rhythms respond to the timing of nutrient delivery/availability. Few studies have examined rhythms in metabolism within human skeletal muscle, providing opportunities to advance current understanding of how nutrient timing affects muscle metabolism.

Evaluating circadian light hygiene: Methodology and health implications

Background — A growing body of research demonstrates that a substantial daily range of light exposure, characterized by ample daylight followed by darkness during sleep, is essential for human well-being. This encompasses crucial aspects like sleep quality, mood regulation, and cardiovascular and metabolic health. Objective — This study characterizes Circadian Light Hygiene (CLH) as an essential factor in maintaining health, well-being, and longevity in modern society. CLH involves adjusting the 24-hour light exposure dynamic range to support the natural sleep-wake cycle and circadian rhythms. Three major challenges to CLH negatively impacting human health are: 1) light pollution (light at night, or LAN), characterized by excessive evening and nighttime artificial light; 2) insufficient natural daylight; and 3) irregular light exposure patterns. These interacting challenges necessitate a systematic approach to measurement and analysis. Material and Methods — A systematic review of peer-reviewed literature published through October 30, 2024, examined the methodologies and health effects of circadian and seasonal aspects of light exposure. Conclusion — This review elucidates fundamental principles of circadian light hygiene, synthesizing existing literature and our research to assess the benefits of adequate daylight, the risks of light at night, and adverse outcomes stemming from diminished light exposure range, mistimed light exposure, and irregular patterns. Novel indices for quantifying and optimizing circadian light hygiene are introduced.

Circadian Deregulation: Back Facing the Sun Toward Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD) Development

Earth's rotation around its axis has pressured its inhabitants to adapt to 24 h cycles of day and night. Humans adapted their own circadian rhythms to the Earth's rhythms with a light-aligned awake-sleep cycle. As a consequence, metabolism undergoes drastic changes throughout the circadian cycle and needs plasticity to cope with opposing conditions in the day (when there is an increase in energy demands and food availability), and during the night (when prolonged fasting couples with cyclic changes in the energy demands across the sleep stages). In the last century, human behavior changed dramatically with a disregard for the natural circadian cycles. This misalignment in sleep and eating schedules strongly modulates the metabolism and energy homeostasis, favoring the development of obesity, metabolic syndrome, and metabolic dysfunction-associated steatotic liver disease (MASLD). This review summarizes the effects of circadian disruption, with a particular focus on the feeding and sleep cycles in the development of MASLD and hepatocellular carcinoma.