26/09/2025
Chronobiology is the scientific field that studies how biological processes are organised in time and regulated by internal clocks. These rhythms influence sleep-wake cycles, hormone secretion, metabolism, immune function and behaviour. Chronobiology also explores how internal clocks interact with environmental cues (like light, food and temperature), and how disruptions (such as shift work, jet lag or disease) affect health.
The evidence is accumulating that artificial light at night does far more than just disrupt sleep. Studies show that the glow from devices, streetlights, and other night-time sources confuses the body’s natural rhythms, which evolved to synchronise with the periods of light and darkness.
A recent ‘Genomic Press Innovators and Ideas’ feature in Brain Medicine profiled the groundbreaking work of neuroscientist Dr. Randy J. Nelson, focusing on his research into the far-reaching effects of disrupted circadian rhythms on both brain performance and overall health. As the current chair of the Department of Neuroscience at West Virginia University, he has devoted the past ten years to uncovering the lesser-known risks posed by exposure to artificial light at night. His studies reveal that night-time light does much more than reduce sleep quality; it can impair immune responses, spark neuroinflammation, interfere with metabolic processes and alter mood regulation. For example, clear links between circadian disruption and metabolic disorders have been found, potentially contributing to the obesity epidemic. Perhaps most concerningly, the research shows direct effects on mood regulation, with implications for understanding depression and anxiety disorders.
“Circadian rhythms are a fundamental aspect of biology, and much is known from foundational science about them,” Dr. Nelson explains. “However, little of this foundational science has been translated to clinical medicine.”
The research also extends to healthcare workers themselves. One clinical trial is investigating whether blue light visors can help night shift nurses reset their circadian rhythms, potentially improving their sleep quality, cognitive performance and mood. Could similar interventions help other shift workers across various industries maintain better health despite irregular schedules?
One of Dr. Nelson’s most provocative proposals involves recognising time-of-day as a crucial biological variable in all research. He argues that experimental results can vary dramatically depending on when studies are conducted, yet this information rarely appears in scientific publications.
“The answer to an experimental question may depend in part on the time-of-day when the question is asked,” Dr. Nelson notes. This observation has profound implications for research reproducibility and could explain why some studies fail to replicate previous findings.
This research carries immediate practical implications for public health. Simple interventions like reducing evening screen time, using warmer light colours after sunset, and maintaining consistent sleep schedules could significantly impact health. His work suggests that respecting our evolutionary heritage by aligning modern life more closely with natural light patterns could prevent numerous chronic health conditions. Nelson recently published a book with Oxford University Press entitled, “Dark Matters,” to help the general public appreciate the importance of good circadian hygiene for health and wellness.
I am growing increasingly interested in the concept that, due to artificial lighting, modern living has led to a deficiency of melatonin exposure. This chemical (and indeed phytochemical) is not just a sleep hormone, but functions as a mitochondria-targeted antioxidant, anti-inflammatory, neuroprotective, and immune and cardiometabolic regulator. These pleiotropic benefits make it a compound of interest in healthspan medicine, chronic disease prevention (including cancer and cognitive decline), and mitochondrial therapy. My preference is to supplement with phytomelatonin.
For more information see: https://scitechdaily.com/the-surprising-ways-nighttime-light-wrecks-your-brain-and-body/
