Guys, if you’re hanging on to a habit of taking your phone to bed with you, you’ll want to pay attention to this news: scientists have linked nighttime blue light exposure to an increased risk for prostate cancer.

What is blue light? It’s a short-wavelength light that science had demonstrated is particularly harmful to sleep. Many of today’s most common light sources, including digital and electronic devices and energy-efficient LED lightbulbs, are what’s known as “short-wavelength enriched.” That means they have higher concentrations of blue light. And that means these days, we’re exposed to more blue light than folks were in the pre-digital age.

A just-released study by European scientists at the Barcelona Institute for Global Health found that men who are exposed at night to higher amounts of blue-light-rich artificial light may double their risk of prostate cancer.

Smartphones are one rich source of artificial, blue wavelength light. And because these addictive little devices go almost everywhere with us—often, even into our bedrooms at night—they can pose particular risks to sleep and health.

But smartphones aren’t the only potentially problematic source of blue light. Tablet and computer screens, high-efficiency lightbulbs, and even environmentally-friendly streetlamps can be sources of bright, sleep-disruptive artificial light at night. In their study, the Barcelona Institute scientists took into account both indoor and outdoor exposure to artificial light.

They found that men who had very bright indoor nighttime environments and men who lived in areas with heavy concentrations of outdoor light were at higher risk for prostate cancer. Women, you’re not excluded from your own risks—the study also found women in these bright-light environments, both indoor and outdoor, had 1.5 times greater risk for breast cancer.

What makes blue light so harmful to sleep? Scientists discovered we have a certain type of photoreceptor cells in our eyes, which make us especially sensitive to the effects of blue light:

  • Blue light is especially aggressive in stopping the release of melatonin, which is known as the “sleep hormone.” At night, our bodies increase their production of melatonin. If that evening melatonin surge doesn’t happen, we have a much harder time falling asleep.
  • Blue light also throws circadian rhythms out of sync. Too much nighttime exposure to any type of artificial light can cause trouble for circadian rhythms and sleep. But blue light has an especially strong effect on circadian rhythms, according to research.

So, what are we supposed to do about this blue light problem? The Barcelona study found that using dark curtains or shades in bright environments lowered men’s risk of prostate cancer. Protecting the darkness of our bedrooms from the light outside is one step we can take. Sleep experts also tell us to follow these guidelines:

  • During evening hours, take advantage of blue-light blocking filters on our smartphones, tablets, and other screens.
  • The closer it gets to bedtime, the less screen time we should indulge in. And keeping electronics out of the bedroom altogether is ideal, experts say.
  • Get plenty of bright light exposure during the day, when we need it to stay alert. This also helps us sleep better at night.

Bottom line? Stash your phone somewhere other than your bedside table. Twitter and Instagram will be waiting for you in the morning.

Written by Caitlin Reynolds