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Night-time Screen-time and Cancer Risk

 

Among non-communicable diseases, cancer is the leading cause of morbidity and mortality worldwide. It is estimated that in 10 years, the number of new cases diagnosed per year will approximately double. If there was a simple change you could make in your life that would reduce your risk of developing cancer would you do it?

 

Most of us are familiar with reducing our animal product intake, increasing our physical activity, taking our vitamin D, reducing exposure to chemicals in our homes, but what about reducing your screen time, particularly at night? Most of our digital devices emit what is called blue light. Blue light has a shorter wavelength than other colours in the visible spectrum, and is not restricted from entering the eye, like other wavelengths are, therefore is able to cause more damage.

 

Before the invention of the lightbulb, humans were exposed to insignificant amounts of light at night. As the sun sets a small gland in our brain starts to make hormone called melatonin, which helps us fall asleep and stay asleep, among other things. Today, we are exposed to artificial light nightly from street lights that shine into our bedroom window, cellphones, laptops, tablets, LED lights, fluorescent lights, you get the idea. There is no need to conduct our lives according to the sun and moon cycle anymore. This means our circadian rhythm gets disrupted, especially in those who work shiftwork.  Exposure to artificial light at night increases your risk of cancer by suppressing melatonin production. Melatonin is an antioxidant that protects us from dangerous reactive oxygen species (ROS).  When our melatonin levels are insufficient, ROS increase in circulation and damage our DNA. If not repaired by intrinsic cellular mechanisms, it will lead to cancer. Another mechanism by which low levels of endogenous melatonin increases cancer risk is via reproductive hormones. Sufficient levels of circulating melatonin actually inhibit the synthesis of estrogen and interfere with estrogen binding at cellular estrogen receptors. This means that insufficient levels of melatonin result in greater risk of hormone responsive cancers like breast, prostate, uterine and ovarian.

 

Large scale studies have found 1.5-2.0 fold increased risk of cancer in countries with more artificial light pollution, even after statistics were adjusted for age, population size, air pollution, and electricity consumption. I certainly don’t believe this is the only cause, but it is a contributing factor.

 

How do we fix this? Well, once the sun sets it’s a good idea to start dimming the lights in your home. Candles make a great natural light source. Use light bulbs with a wavelength emission peak of 470-480nm, instead of those with a peak below 450nm. Spend more time outside exposing your eyes to natural light. Reducing screen time after dinner, and completely shutting down electronics an hour or two before bed is also important. I’ll be the first to admit that I regularly use my computer after dark, especially in the fall and winter, to do research, or write things like this article. Thankfully there are glasses you can wear to reduce your exposure to blue light. My favourite is Ladyboss Glasses (no, I do not work for the company). You can also turn on the night setting on your mobile device during the day.

 

While the use of indoor lighting and mobile devices has certainly allowed humans to accomplish much more in a day, it is also important for us to do nothing once in a while, to step back from the hustle of the day and relax.

 

Dr. Brenda Tapp ND