For thousands of years, the rising and setting sun governed human biology. Now, researchers are uncovering how recreating these natural light cycles can dramatically improve our health in the modern world.
The Evolutionary Basis of Light's Impact on Health
Long before the invention of artificial lighting, humans evolved intricate biological rhythms tied to the daily cycles of sunlight. The warm red and orange hues of dawn and dusk acted as powerful cues to regulate our circadian rhythms, hormones, and countless other physiological processes.
Dr. Richard Stevens, cancer epidemiologist at the University of Connecticut, explains:
"Electric lights, especially at night, disrupt circadian rhythms through melatonin suppression and phase shifting. The health consequences are broad, including sleep disruption, depression, cardiovascular disease, and cancer."1
By understanding and recreating the essential wavelengths of natural light cycles, we may be able to mitigate many of the health issues caused by modern lighting and screen use.
The Science Behind Dawn and Dusk Light
Recent research has identified the specific light wavelengths that most powerfully influence our circadian biology:
Blue light (450-495 nm): Suppresses melatonin production, increases alertness
Green light (495-570 nm): Improves alertness and cognitive performance
Red/near-infrared light (600-1000 nm): Stimulates mitochondrial function, promotes healing
A groundbreaking 2019 study by Bromundt et al. found that simulating natural dawn-dusk cycles using these wavelengths produced significant benefits in dementia patients:
"Dawn-dusk simulation led to significantly better mood in the morning hours after waking. The effects were most pronounced in the second 4 weeks with DDS, indicating that positive effects emerged gradually."2
The researchers concluded that "continuous, long-term application of dawn-dusk simulation at the sleep-wake transitions appears to increase external zeitgeber strength" - essentially reinforcing the body's natural circadian rhythms.
Incorporating Natural Light Cycles in Modern Life
While getting outside for actual sunrise and sunset is ideal, there are several ways to mimic these beneficial light wavelengths in our indoor environments:
Use red/amber lighting in the evening hours
Install dawn simulator alarm clocks
Wear blue-blocking glasses after sundown
Enable Night Shift/f.lux on devices to filter blue light
Use red night lights instead of white/blue
Consider light therapy boxes for morning light exposure
Dr. George Brainard, Director of the Light Research Program at Thomas Jefferson University, advises: "The key is to get bright light, preferably sunlight, during the day and then dim, longer wavelength light in the evening. This will help keep your circadian rhythms appropriately synchronized."3
Therapeutic Applications of Light
Beyond general wellness, targeted light therapy shows promise for treating various health conditions:
Non-seasonal depression
Sleep disorders
A 2003 study by Fontana Gasio et al. found that even low-intensity dawn-dusk simulation improved sleep timing and quality in elderly dementia patients:
"The main sleep episode was 1:14h earlier during treatment (p=0.03) compared with before and after DDS. With respect to actimetry-determined sleep variables, the DDS group tended to have shortened 'sleep latency', longer 'sleep duration', more nocturnal immobility and less nocturnal activity than the dim red group (p<0.1)."4
Conclusion
By understanding and harnessing the power of natural light cycles, we can dramatically improve our health and wellbeing in the modern world. Simple changes to our light environment - both during the day and at night - can help realign our bodies with the rhythms we evolved with for millennia. As research in this field progresses, light-based therapies are likely to play an increasingly important role in both preventative health and medical treatments.
Interested in learning more about photobiomodulation? Watch Sayer Ji's latest interview with Dr. Christopher D' Amado, PhD on the topic here.
References
1. Stevens, Richard G., et al. "Adverse health effects of nighttime lighting: comments on American Medical Association policy statement." American journal of preventive medicine 45.3 (2013): 343-346.
2. Bromundt, Vivien, et al. "Effects of a dawn-dusk simulation on circadian rest-activity cycles, sleep, mood and well-being in dementia patients." Experimental gerontology 124 (2019): 110641.
3. Brainard, George C., et al. "Action spectrum for melatonin regulation in humans: evidence for a novel circadian photoreceptor." Journal of Neuroscience 21.16 (2001): 6405-6412.
4. Fontana Gasio, Paola, et al. "Dawn-dusk simulation light therapy of disturbed circadian rest-activity cycles in demented elderly." Experimental gerontology 38.1-2 (2003): 207-216.
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