Sleep quality and health can be affected by exposure to different light-emitting devices. Exposure to short-wavelength-enriched (blue-enriched) light in the evening increases alertness and suppresses the production of melatonin, which is only produced during sleeping hours and helps regulate the sleep-wake cycle.

In this study, Gringras et al reveals the spectral profiles of the most popular devices in 2014: the iPad Air, the iPhone 5s, and the Kindle Paperwhite 1st generation. The difference in light signals emitted from a popular game (Angry Birds) and e-book text was also compared. The default brightness levels were used for the iPhone and iPad, and 50% brightness was used for the Kindle based on convenience sampling from users. Irradiance was measured as an exact spectral power distribution (SPD) using a spectrometer. The spectral profiles were similar across all devices, and between Angry Birds and e-book text. The intensity level was higher for the iPad.

ipad at night

Two strategies to reduce the impact of short-wavelength enriched light emissions were tested. First, the blue-blocking, orange-tinted Pyramex Ztek Safety Eyewear was very effective in decreasing the intensity of the short-wavelength/blue light emissions. Second, the Kids Sleep Dr app, which allowed for selection of a “sleep-aware” palate of colors on the device, was also successful in reducing short-wavelength light emissions, but also changed the spectral profile completely.

ipad at night

The authors have collected the following recommendations to avoid letting light-emitting devices affect sleep quality and health:

  • Avoid light-emitting devices 2-3 hours before bedtime (Harvard Medical School)
  • Turn off all electronic devices at least 1 hour before bedtime (National Sleep Foundation)
  • Consider wearing commercially available and affordable orange-tinted glasses when looking at light-emitting devices at night
  • Use apps like the “sleep-aware” app at night to adjust the displayed color scheme
  • Use software like F.lux that filters the emission spectrum of the device (currently only available on Android devices. To get this device on your iPhone or iPad you would have to jailbreak it since Apple does not allow F.lux or other companies to change the display colors on the screen).

It is important to keep in mind that although resources to decrease the short-wavelength emission levels are available, increased duration of exposure to low levels of these blue lights will still suppress melatonin levels and increase alertness at night time.

The orange tinted glasses the study mentions are just $5.53 on Amazon right now.  While the study did specify a specific brand, they didn’t say the orange tint had to be exclusive to those glasses.

Frankly though, if improving sleep is a serious priority — you shouldn’t be using your iPad or smartphone devices at night. As we’ve written before, the best way to improve sleep is to focus on sleep hygiene.  There are several sleep apps available as well to help with sleep hygiene.