Lights Out: The Unseen Dangers of Artificial Light and Cancer

Since Thomas Edison first introduced electric light bulbs nearly one century ago, our lives have never been the same. Light has enabled us to fight darkness and live according to our own schedule rather than that dictated by nature; today it would be difficult to imagine life without bright city lights or phone screens lit late into the night.

But all of this light may also come at a cost we never expected. Recent studies, like those by Verywell Health, indicate that too much artificial illumination after dark could increase cancer risks significantly. We explore this topic here – how the bright lights that bring us so many conveniences might also be negatively affecting our health in ways we never imagined.

Science of Light and Biological Rhythms

Our bodies function on an internal 24-hour clock known as the circadian rhythm, telling us when it’s time for wakeup and nap time – but here’s where things get tricky: the blue light from smartphones, tablets, and LED lights is often enough an alarm that disrupts this natural cycle.

At night, prolonged exposure to blue light causes our bodies to think it’s still daytime, leading us to stay up past bedtime and disrupting hormones such as melatonin production – our natural sleep hormone with anticancer properties and associated sleep disruption – but when our eyes stay glued on screens too late into the evening our brains get the signal to cut back production of this essential hormone – meaning less sleep might ensue as well as missed opportunities to use its potential against cancer.

Studies of Artificial Light at Night

There is mounting scientific evidence supporting the link between artificial lighting at night (ALAN) and cancer risks, particularly breast cancer risk. A major study published in the International Journal of Cancer showed that women living in areas with higher outdoor light levels at night had an increased risk of breast cancer – even taking into account age, weight and smoking status factors as variables in its findings. This finding proved the correlation between light exposure and cancer risks.
No only outdoor lighting should be of concern; indoor artificial light also requires consideration. Research published in Environmental Health Perspectives revealed that men exposed to higher levels of indoor artificial lighting had an increased risk of prostate cancer; similar patterns were noted among women, further supporting the belief that excessive light exposure at night is a universal health concern.

The mechanisms behind cancer appear to be connected with hormonal imbalances. Our bodies rely on natural light-dark cycles for regulating hormone production, including melatonin. Melatonin is best known as an aid to sleeping but also plays a part in controlling other hormones which could impact cancer growth; when artificial lights disrupt circadian rhythms it reduces production, which could in turn disturb hormonal equilibrium and raise risk.

These findings highlight an aspect of modern living that we often take for granted: artificial lighting has an immense effect on health, making awareness about its consequences increasingly crucial. According to studies, additional awareness needs to be created on night-time exposure levels for optimal wellbeing.

Mitigating Risks: Practical Tips

Though modern life cannot allow us to turn off every light at night, there are practical steps we can take to limit exposure to artificial lighting at night and decrease potential health risks. Below are a few simple suggestions:

  • Try Using Blue Light Filters: With many electronic devices now offering features or apps designed to reduce blue light exposure, take advantage of them during evening hours by activating these features. Blue Light Blocking Eyewear is another option.
  • Adopt Dim Red Lights for Nighttime: When selecting a night light, red bulbs have the least potential to alter circadian rhythm and suppress melatonin production.
  • Limit Screen Time Before Bed: For optimal sleeping patterns, electronic devices like smartphones, tablets and laptops should be shut off at least an hour before turning in for the night. Blue light emitting from screens has an especially negative impact on our rest cycles.
  • Create a Dark Bedroom Environment: For optimal sleep and circadian rhythm disruption, invest in blackout curtains or shades that block light coming through streetlights or passing cars. Any additional light sources could alter your melatonin production and sleep patterns.
  • Establish a Regular Sleep Routine: Strengthen your natural circadian rhythms by keeping a set bedtime/wakeup time schedule.
  • Opt for Low Wattage Bulbs: For intimate and relaxing indoor lighting before bedtime, lower-wattage bulbs offer the best solution. Their lower brightness levels help create an intimate setting that promotes relaxation.

The Bottom Line

Light bulbs’ legacy includes one less glamorous side effect – their potential adverse impact on health, particularly regarding cancer risks. While modern life cannot be avoided entirely, understanding how artificial lighting impacts biological rhythms empowers us to make wiser choices regarding nightly routines and environments to mitigate cancer risk. Not just better sleep – protecting long-term health is paramount here! As research continues to shed more light on this subject matter, let us all take action – starting tonight – that can reduce unnecessary lighting exposures to protect ourselves against cancer risks.



Cho Y, Ryu SH, Lee BR, Kim KH, Lee E, Choi J. Effects of artificial light at night on human health: A literature review of observational and experimental studies applied to exposure assessment. Chronobiol Int. 2015;32(9):1294-310. doi: 10.3109/07420528.2015.1073158. Epub 2015 Sep 16. PMID: 26375320.

Urbano T, Vinceti M, Wise LA, Filippini T. Light at night and risk of breast cancer: a systematic review and dose–response meta-analysis. Int J Health Geogr. 2021;20(1):44. doi:10.1186/s12942-021-00297-7

Sweeney MR, Nichols HB, Jones RR, Olshan AF, Keil AP, Engel LS, James P, Jackson CL, Sandler DP, White AJ. Light at night and the risk of breast cancer: Findings from the Sister study. Environ Int. 2022 Nov;169:107495. doi: 10.1016/j.envint.2022.107495. Epub 2022 Sep 2. PMID: 36084405; PMCID: PMC9561075.

Barul C, Richard H, Parent ME. Night-shift work and risk of prostate cancer: results from a Canadian case-control study, the prostate cancer and environment study. Am J Epidemiol. 2019;188(10):1801-1811. doi:10.1093/aje/kwz167

James P, Bertrand KA, Hart JE, Schernhammer ES, Tamimi RM, Laden F. Outdoor Light at Night and Breast Cancer Incidence in the Nurses’ Health Study II. Environ Health Perspect. 2017 Aug 17;125(8):087010. doi: 10.1289/EHP935. PMID: 28886600; PMCID: PMC5783660.

Hurley S, Goldberg D, Nelson D, Hertz A, Horn-Ross PL, Bernstein L, Reynolds P. Light at night and breast cancer risk among California teachers. Epidemiology. 2014 Sep;25(5):697-706. doi: 10.1097/EDE.0000000000000137. PMID: 25061924; PMCID: PMC4130422.


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