Two hours of using your tablet computer at night could end up disturbing your sleep. Researchers from Rensselaer Polytechnic Institute's Lighting Research Center found that the light from using a tablet PC for just two hours lowers melatonin production by about 22%, which could make it a lot harder to get to sleep afterwards.
The researchers suggest minimizing tablet use at night or dimming them as much as possible for people who want to get a good night's sleep.
It is not only how long you use the tablet at night that matters, it's also what you're looking at that's likely to determine how much your sleep will be affected.
The researchers looked at 13 people who each used their tablet computers under three different conditions. First, people used the tablets as they normally would, reading, playing games and watching movies, with brightness at maximum. Then they used them while wearing orange-tinted goggles, which filter out all blue light. Blue light is especially potent at suppressing melatonin production. Finally, they used their tablets while wearing clear goggles equipped with blue light-emitting diodes (470 nm, 40 lux), ensuring that the people were getting a healthy dose of blue light while using the tablets.
Melatonin is a hormone produced by the pineal gland at night and in the dark that helps set the body's biological clock. Disrupting this clock can lead to sleep disturbances and potentially more serious complications if the disruptions continue for long periods of time, as they do for shift workers.
Another finding was that the amount of light reaching the eye can vary 10-fold, from 5 lux to over 50, depending on exactly what images people are viewing on the screen. So it's not only how long you use the tablet at night that matters, it's also what you're looking at that's likely to determine how much your sleep will be affected.
The researchers hope these findings will lead to production of more circadian-friendly electronic devices, possibly models that will automatically emit more light during the day and less at night.
An article on the study was published online by Applied Ergonomics.