Having a T.V. in the bedroom is recognised as being bad for sleep and your mood. But now there is a new pest lurking to disturb your sleep pattern. It's smaller than the T.V. but no less disruptive - it's the iPad.
My husband was given an iPad for Christmas, which he was delighted with. So delighted that he takes it to bed with him for a quick check on his emails or brief internet interlude before snuggling down under the doona. What I noticed other than I was now sharing the bed with a computer tablet as well as my husband, was the intensity of the light on the screen. I usually like to read before sleep and being of the old fashioned type, I still prefer to hold a book. But now I found that I almost didn't need the bedside light anymore because of those blueish rays emanating in an UFO kind of way from the other side of the bed.
So is this a problem?
Researchers indicate yes it is because the blueish light of the screen mimics daylight and stimulates the brain into thinking it is still daytime by suppressing the body's natural production of melatonin.
Working late at night on a computer or watching late night movies on the T.V. is bad for the same reason. The issue with the iPad is that by being so small and portable, we take it into our den, the place that really should be reserved just for sleeping. (By the way this goes for mobile phones as well.)
Researchers suggest melatonin suppression occurs after just two hours exposure to the iPad display.
The suggestion to minimise sleep disturbances would be
1. Turn the appliance off at the end of the working day and don’t use it late at night.
2. Dim the screen. Kindle has a much kinder screen appearance with a more yellow background which is softer on the eyes and less disruptive to sleep.
3. Buy yourself a pair of orange goggles to cut out the blue light. Hmm, this might be on the next year's Christmas list, if not purchased before.
The other concern about continued exposure to bright light late at night relates to mood disturbance and it's not crankiness due to the disturbed sleep either.
Researchers from John Hopkins University recently published their findings in Nature. They have found that chronic exposure to bright light (in any form) impacts the brain's limbic system via highly specialised intrinsic photosensitive retinal ganglion cells and leads to elevated cortisol levels. Cortisol is a stress hormone, which in excess can impair memory and learning and contribute to the development of depression.
Whilst the studies were performed in mice, the researchers say that humans have the same specialised retinal cells, which are likely to respond to exposure to bright light in the same way.
You may have heard of melatonin in relation to sleep and jet lag. It is a hormone produced in the tiny pineal gland in the brain. Its production is triggered by darkness and leads to sleep, lower blood pressure and body temperature.
This research could be relevant in the workplace, especially to those working night shift or night owls burning the midnight oil over their keypad.
Moreover the study found that the irregular light schedules directly affected mood and cognitive function, independent of sleep and circadian rhythms.
Those mice then given Prozac regained their ability to learn, which suggests that the depressive effect precedes the learning impairment.
Bearing in mind this research was carried out in mice, it cannot be said using an iPad as a human can lead to mood disturbance. What was shown was that animals i.e. mice exposed to an abnormal light pattern produced higher levels of a stress hormone and appeared less capable of functioning as well cognitively compared to control group mice. The correlation to humans cannot be made until the appropriate studies have been carried out. However the suggestion is that if we choose to radically change our sleep/wake habits and be exposed to chronic light exposure, whether it be through staying up late or working through the night on computers and iPads, we may be influencing our brain's ability to function normally. It is certainly no secret that sleep distrurbance and deprivation is associated with poorer cognitive function and a negative effect on mood.
Perhaps I need to ensure that my husband does keep his new tablet out of the bedroom and then hopefully we will both enjoy a better night's sleep.
Figueiro, M.G et al (2012) Light level and duration of exposure determine the impact of self-luminous tablets on melatonin suppression. Applied Ergonomics ()
Hattar, Samer. et al.(2012) Aberrant light directly impairs mood and learning through melanopsin-expressing neurons. Nature 491, 594–598 doi:10.1038/nature11673