The Impact of Brighter Nights and Darker Days on Early Mortality
Excessive exposure to light at night and insufficient exposure during the day can disrupt circadian rhythms, leading to poor health outcomes and an increased risk of death.
Optimizing light exposure is crucial for maintaining health.
Understanding the Impact of Light Exposure
The study delved into how light exposure affects mortality from cardiometabolic risk factors, encompassing conditions that affect the heart, blood, and blood vessels, like obesity, high blood pressure, unhealthy cholesterol, and elevated blood sugar levels.
With data from light sensors worn for a week by approximately 89,000 participants, totaling 13 million hours, researchers compared the light information with death records from the National Health Service spanning around eight years. They also gauged sleep duration and efficiency from motion data.
The findings revealed that light exposure can enhance or disrupt circadian rhythms depending on the timing. These rhythms govern the variations individuals experience over a day, influencing functions like sleep, digestion, hormone release, and body temperature.
Participants exposed to brighter daylight had death rates reduced by 17–34 percent, with the effects being dosage-dependent—higher exposure correlating with lower risks. Conversely, those exposed to brighter nighttime light had death rates elevated by 21–34 percent, with higher exposure leading to greater risks. The heightened risk of death encompassed all causes, particularly cardiometabolic disease.
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“Minimizing nighttime light exposure, maximizing daytime light exposure, and maintaining regular light-dark patterns that support circadian rhythms can enhance cardiometabolic health and longevity,” the researchers concluded.
Effects of Disrupted Circadian Rhythms
The study underscores the pivotal role of circadian rhythms in the impact of light exposure on health. These rhythms are regulated by circadian clock genes, with a brain structure known as the master clock coordinating their harmonious functioning. Any disruption, such as exposure to light before sleep, can derail a rhythm, heightening health risks.
Prior research correlated disrupted circadian rhythms with the onset of conditions like obesity, diabetes, and metabolic syndrome—an amalgamation of abnormalities increasing the chances of heart disease and diabetes.
Conversely, reinforced circadian rhythms might explain the association between increased daytime light exposure and reduced mortality risk. Strengthened rhythms could also confer protection against the adverse effects of disrupted circadian rhythms.
Supporting Evidence
Earlier investigations involving night owls and shift workers offer corroborative evidence to the study’s findings.
Night Owls
A study published in Chronobiology International explored the connection between death risk and individuals with a preference for later sleep times, known as evening types or night owls.
Shift Workers
A study published in the American Journal of Preventive Medicine assessed the impact of shift work on mortality risk using data from 74,862 registered nurses in the Nurses’ Health Study.
Tips for Light Exposure
Bjørn Ekeberg, co-founder and CEO of Recharge Health, creator of FlexBeam, and an international light expert, shared light exposure tips with The Epoch Times via email.
- Try to get 15–30 minutes of sunlight exposure early in the day to improve overall health, as it plays a role in setting circadian rhythms.
- If adequate sunlight exposure is not feasible, consider a 10-minute session of red-light therapy during the day, as red and near-infrared light exposure can be beneficial. It’s best to do this early in the day when the sun naturally emits these wavelengths. Red light therapy lacks blue light that disrupts sleep and can be used safely.
- Before bedtime, particularly 1–2 hours before, minimize exposure to artificial light sources, like TV, computer, and cell phone screens, as these emit blue light that stimulates the brain and eyes, interfering with melatonin production essential for sleep.
- Avoid overhead LED lights in the evening, as they emit distorted and unnatural wavelengths. The body is more sensitive to light from above than below, making overhead lighting more impactful.
- To transition into bedtime mode, dim direct light sources like screens and lamps, opt for warm-tone lighting instead of bright ceiling lights.
Natural vs. Artificial Light
“The world heavily relies on sunlight,” according to Ekeberg. “Just like plants, humans need the sun’s energy.”
Skin exposure to sunlight provides an energy source that the body can convert, enhancing circadian rhythms and regulating wake-sleep cycles directly.
Ekeberg explains that sunlight encompasses the full electromagnetic spectrum, from ultraviolet rays through visible light (blue, green, red) to infrared wavelengths. Sunlight exposure ensures a complete range of beneficial light, notably red and near-infrared wavelengths.
On the other hand, indoor lighting, especially LED lights, primarily emit visible light and are high in blue wavelengths that can disrupt circadian rhythms during dark hours, Ekeberg noted.
“Indoor lighting is designed for visibility, not as a substitute for natural sunlight, which confers health benefits while excessive indoor lighting can be detrimental,” he added.
