People obsessed by their smartphones or tablets should wear special computer glasses or use screen filters to block out blue light to get a good night’s sleep.
If they use these filters three hours before bed, they will see levels of their sleep hormone increase by nearly three fifths, sleep better and nod off quicker and get an extra 24 minutes sleep a night.
The ubiquitous digital gadgets are always on hand and the temptation is to use them just before we go to bed.
The largest source of blue light is sunlight and it boosts alertness and regulates our internal body clock that tells our bodies when to sleep.
But the blue light emitted from most LED-based devices disrupts sleep by suppressing the sleep hormone melatonin leaving many tired out in the morning.
Lead author Assistant Professor Dr Lisa Ostrin said to avoid sleep disturbances, people should limit their screen time, apply screen filters, wear computer glasses that block blue light, or use anti-reflective lenses to offset the effects of artificial light at nighttime.
Some devices even include night mode settings that limit blue light exposure.
Prof Ostrin of the University of Houston College of Optometry said: “Exposure to increasing amounts of artificial light during the night may contribute to the high prevalence of reported sleep dysfunction.
“Release of the sleep hormone melatonin is mediated by the intrinsically photosensitive retinal ganglion cells (ipRGCs).
“This study sought to investigate whether melatonin level and sleep quality can be modulated by decreasing night-time input to the ipRGCs.
It gave 22 participants aged 17 to 42 short wavelength-blocking glasses three hours before bedtime for two weeks while still performing their nightly digital routine.
They also wore activity, light exposure and sleep monitors 24 hours a day during the study period.
Saliva samples were collected to assess melatonin content, sleep quality assessed by using The Pittsburgh Sleep Quality Index and pupil dilation measured.
All had about a 58 per cent increase in their nighttime melatonin levels, the chemical that signals your body that it’s time to sleep.
And levels were even higher than increases from over-the-counter melatonin supplements.
All participants also reported sleeping better, falling asleep faster, and even increased their sleep duration by 24 minutes a night from an average six hours and 48 minutes hours to seven hours and 11 minutes.
They also had slower redilation phase.
Prof Ostrin said: “The most important takeaway is that blue light at night time really does decrease sleep quality.
“Sleep is very important for the regeneration of many functions in our body.
“By using blue blocking glasses we are decreasing input to the photoreceptors, so we can improve sleep and still continue to use our devices.
“That’s nice, because we can still be productive at night.”
She concluded: “The use of short wavelength-blocking glasses at night increased subjectively measured sleep quality and objectively measured melatonin levels and sleep duration, presumably as a result of decreased night-time stimulation of ipRGCs.
“Alterations in the ipRGC-driven pupil response suggest a shift in circadian phase.
“Results suggest that minimising short wavelength light following sunset may help in regulating sleep patterns.”
The study was published in Ophthalmic & Physiological Optics.