Blue light like that from smartphones linked to some cancers, study finds

The article [below] is from; below the layman’s article is the Abstract of the scientific paper that just appeared in Environ Health Perspect. At this point, I’ll just share this news article, as is, and sit back and wait to hear from those who wish to weigh in on the scientific validity vs the rigor of the epidemiological methods used vs the hype and hysteria that this kind of article tends to generate…..

Blue light like that from smartphones linked to some cancers, study finds

The Sixth Street bridge over the Los Angeles River looks a bit different with old, left, and new streetlights.

Photos: Los Angeles LED streetlights. The Sixth Street bridge over the Los Angeles River looks a bit different with old, left, and new streetlights.

· People exposed to higher levels of blue light were at more risk of breast and prostate cancer.


· Those exposed to LEDs with less blue in them did not see an increased risk of cancer.

(CNN) Exposure to the kind of blue light emitted by outdoor LEDs, smartphones and tablets may increase your risk of breast or prostate cancer, a new study suggests. The study, published Monday in the journal Environmental Health Perspectives, compared previous exposure to artificial lights at night between approximately 2,000 breast, or prostate, cancer patients and approximately 2,000 controls living in Barcelona and Madrid.

The researchers measured exposure to outdoor artificial light, such as streetlights, using images from the International Space Station and to indoor artificial light using self-reported questionnaires. The researchers found that those exposed to high levels of outdoor blue light at night had around a 1.5-fold higher risk of developing breast cancer and a twofold higher risk of developing prostate cancer, compared with those who were less exposed. Men exposed to high levels of indoor artificial light also had 2.8-fold higher risk of developing prostate cancer, according to the study.

“The real breakthrough of this study is that, for the first time, we can see directly the color in higher resolution and relate it to individual cases,” said Alejandro Sánchez de Miguel, a researcher at the Environment and Sustainability Institute at the University of Exeter and a lead author on the study.

Though previous studies have used satellite imagery to calculate the intensity of artificial light at night in large cities, the new study is the first to look specifically at the amount of blue light, according to Sánchez de Miguel. “In this study, we focused on the satellite images, because other satellites cannot see the colors,” but astronauts aboard the space station can, he added. “And so this is the first study to put an experimental value on the correlation between blue light in the general population with the risk of breast cancer and prostate cancer.”

But exposure to other kinds of outdoor artificial light — such as those that are high in the red and green portions of the visible spectrum — was not positively associated with the development of either type of cancer, the study states.

“That finding was unexpected but suggests that it is really the blue light that is important for cancer rather than just general brightness of light,” said Kristen Knutson, associate professor of neurology at Northwestern University’s Feinberg School of Medicine, who was not involved in the new study.

Blue light has a shorter wavelength than other light in the visible spectrum, meaning it has more energy than other types of visible light. Exposure to blue light is known to decrease the release of melatonin in the brain, which helps regulate the body’s circadian rhythm, according to Knutson.

“Blue light is the spectrum that signals the clock in the brain, and it is the spectrum that suppresses melatonin,” she said. “Melatonin is a hormone that plays an important role in maintaining the synchronization of the clocks in all our body’s cells. Disruption of these clocks is thought to increase the risk of cancer.”

Melatonin is also known to act as an antioxidant, and adequate levels may be necessary to suppress the growth of certain hormone-sensitive cancers such as breast and prostate cancer, according to Sánchez de Miguel. Blue light is present in some — but not all — outdoor LEDs, particularly those with a color temperature of more than 3,000 degrees Kelvin.

Color temperature measures the spectral content of light: how much blue, green, yellow and red there is in it. A higher color temperature generally correlates with more blue light, according to Richard Stevens, professor of community medicine and health care at the University of Connecticut, who was not involved in the new study.

“The most efficient suppression of melatonin is with that beautiful blue light,” he said. “And if you have a light bulb like a fluorescent that has spikes in that region and you turn it on at night, you’re more likely to suppress melatonin.” Blue light is also produced inside smartphones and tablets. But Sánchez de Miguel cautions that the study looked only at blue light from outdoor LEDs, not smartphones or tablets.

“That is a confusion for many journalists; we have not done anything in phones,” Sánchez de Miguel said. “But the same mechanism may be affecting the phones or the bulbs at home, because the physiology is the same.” The American Medication Association recommends that outdoor LEDs be no greater than 3,000 Kelvin in order to “minimize potential harmful health and environmental effects,” according to a 2016 statement. Some cities, such as Davis, California, have even removed outdoor LEDs and replaced them with ones that have a lower color temperature, according to Stevens.

“The utilities put in these lights — I think they were around 4,000 (Kelvin). And about a third of the way through through the retrofit, there was pushback from the community,” Stevens said. “So the city actually sucked it up … and put in much lower-temperature lights.”

For those who wish to reduce their exposure to blue light from phones and other devices, there are a number of applications available for download, including F.lux, Redshift, SunsetScreen, Iris and Twilight. The iPhones also come with an application called Night Shift that filters out blue light, according to NPR. “I think they’re great,” Stevens said. “They change the spectrum of intensity on the screen depending on time of day, and that’s great. That’s where we need to go in society in general.”

The most recent study was performed in two large cities in Spain, meaning the results may not be generalizable to people living in other areas. But the findings probably still apply to people in other large metropolitan areas, according to Stevens. “Our cities are getting brighter and brighter, and they’re getting brighter throughout the world,” Stevens said. “We do not know if the results for breast cancer or prostate cancer would be replicable, but it’s definitely suggestive.”

Evaluating the Association between Artificial Light-at-Night Exposure and Breast and Prostate Cancer Risk in Spain (MCC-Spain Study)

Ariadna Garcia-Saenz,1,2,3 Alejandro Sánchez de Miguel,4,5,6,7 Ana Espinosa,1,2,3,8 Antonia Valentin,1,3,8 Núria Aragonés,2,9 Javier Llorca,2,10 Pilar Amiano,2,11 Vicente Martín Sánchez,2,12 Marcela Guevara,2,13 Rocío Capelo,14 Adonina Tardón,2,15 Rosana Peiró-Perez,2,16 José Juan Jiménez-Moleón,2,17,18 Aina Roca-Barceló,19Beatriz Pérez-Gómez,2,9 Trinidad Dierssen-Sotos,2,10 Tania Fernández-Villa,2,12 Conchi Moreno-Iribas,13,20Victor Moreno,2,21,22 Javier García-Pérez,2,9 Gemma Castaño-Vinyals,1,2,3,8 Marina Pollán,2,9 Martin Aubé,6and Manolis Kogevinas1,2,3,8

Author Affiliations OPEN

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BACKGROUND: Night shift work, exposure to light at night (ALAN) and circadian disruption may increase the risk of hormone-dependent cancers.
OBJECTIVES: We evaluated the association of exposure to ALAN during sleeping time with breast and prostate cancer in a population based multicase–control study (MCC-Spain), among subjects who had never worked at night. We evaluated chronotype, a characteristic that may relate to adaptation to light at night.
METHODS: We enrolled 1,219 breast cancer cases, 1,385 female controls, 623 prostate cancer cases, and 879 male controls from 11 Spanish regions in 2008–2013. Indoor ALAN information was obtained through questionnaires. Outdoor ALAN was analyzed using images from the International Space Station (ISS) available for Barcelona and Madrid for 2012–2013, including data of remotely sensed upward light intensity and blue light spectrum information for each geocoded longest residence of each MCC-Spain subject.
RESULTS: Among Barcelona and Madrid participants with information on both indoor and outdoor ALAN, exposure to outdoor ALAN in the blue light spectrum was associated with breast cancer [adjusted odds ratio (OR) for highest vs. lowest tertile, OR=1.47; 95% CI: 1.00, 2.17] and prostate cancer (OR=2.05; 95% CI: 1.38, 3.03). In contrast, those exposed to the highest versus lowest intensity of outdoor ALAN were more likely to be controls than cases, particularly for prostate cancer. Compared with those who reported sleeping in total darkness, men who slept in “quite illuminated” bedrooms had a higher risk of prostate cancer (OR=2.79; 95% CI: 1.55, 5.04), whereas women had a slightly lower risk of breast cancer (OR=0.77; 95% CI: 0.39, 1.51).
CONCLUSION: Both prostate and breast cancer were associated with high estimated exposure to outdoor ALAN in the blue-enriched light spectrum.

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