The primary focus of this study was to see how ALAN (artificial light-at-night) can lead to the disruption in an individual's circadian rhythm, which could increase the risk of hormone-dependent cancers. The pineal gland produces melatonin, which is normally secreted during the night phase of the circadian rhythm. According to the International Agency for Research on Cancer (IARC), melatonin is related to cancer in several different ways, one of which is its ability to block estrogen receptors. Similar studies have been conducted on professionals that consistently work night shifts, but what does this mean for the rest of us that have created habits of using ALAN before bed (phones, laptops, kindles, etc.)?
The results of this study revealed that exposure to ALAN during night time does correlate with an increase risk of breast and prostate cancer. More specifically, researcher found that prostate cancer had a higher correlation with outdoor ALAN in the visible spectrum, and that breast cancer had the same high risk correlation with ALAN, but with artificial light in the blue spectrum. The study was conducted via survey in 11 regions throughout Spain using images from the International Space Station (ISS) , so there is a chance that some of the data collected was incorrect.
Though this limitation was mentioned, a big issue I had with this study was that researchers did not look at time spent exposed to ALAN, so there is a chance that accuracy of exposure time did effect on the results. I think that an interesting future study would be test a smaller group of individuals, to see if exposure time can increase the risk of hormone-dependent cancers even more.
Reference: Garcia-Saenz, A., Sánchez de Miguel, A., Espinosa, A., Valentin, A., Aragonés, N., Llorca, J., … García-Pérez, J. (2018). Evaluating the Association between Artificial Light-at-Night Exposure and Breast and Prostate Cancer Risk in Spain (MCC-Spain Study). Environmental Health Perspectives, 126(4), 1–11. Retrieved from https://doi-org.dml.regis.edu/10.1289/EHP1837
I don't quite understand how the ALAN is leading to these types of cancer, does it have something to do with producing different amounts of melanin? Also, how was the Space station able to figure this out with imaging, imaging of what specifically?
ReplyDeleteGood questions, I wrote this late at night so I am glad you pointed out some important missing details!
DeleteThe idea is that ALAN suppresses the amount of melatonin secreted, which have an important role in estrogen-receptor expression. Melatonin is induced during the night phase of the circadian rhythm, so a disruption (ALAN) in this rhythm can also cause a disruption in the excretion of melatonin. There have been previously conducted studies looking the relationship between hormone-dependent cancers and melatonin, but there are a few different mechanism. One of which led them to find estrogen-receptor positive human breast cancer cells. The importance of this is that we know melatonin can work as an estrogen expression suppressor (this info is from previous studies). There have been some cancer treatments that are coupled with melatonin and the results have been promising. The surveys they used to conduct their study was specific to the kinds of indoor light. The ISS images were used to see what kinds of outdoor ALAN (red, blue or green) people were being exposed to at night, since they were trying to estimate the spectrum of light being emitted. The images look like an arial view of the city at night, showing the the lights on around the city.
I hope this helps clarify some things!