Average Reading Time: 2 minutes and 16 seconds
Over the past 50 years, there has been a decline in the average duration and quality of sleep that has been linked to a variety of health concerns. (1) In a recent study, 1508 subjects were surveyed for reading off electronic devices before bed. They found that 90% of Americans use an electronic device for about an hour before bed at least a few nights a week. (1)
A Light-Emitting Device vs. Printed Book Showdown
In the same study, reading off electronic devices before bed was contrasted with reading old-fashioned books or magazines, and the results were surprising. (1) They found that reading off of electronic readers, iPads, cell phones, computers, or just watching TV before bed can disturb the body’s circadian rhythms, decrease melatonin production, and make it more difficult to both fall asleep and wake up. (1, 2)
Twelve adults spent two weeks in a sleep lab reading either a light-emitting device (i.e. iPad or tablet) or printed book for four hours before bedtime for five consecutive evenings. Then, the group of twelve switched reading devices, so that at some point, each reader was tested with both an iPad and a printed book. Bedtime was at 10PM.
The monitors showed that, compared to the printed book readers, the iPad readers:
- Took 10 minutes longer on average to fall asleep.
- Experienced less rapid eye movements (REM) after reading off the iPads.
- Experienced a decrease in melatonin production, delaying the circadian sleep clock by nearly an hour.
The iPad readers also reported that they felt less sleepy before bed after reading from the iPad, and it took them longer to become fully alert in the morning.
The Dangers of Blue Light
The researchers found that the light emitted from electronic devices, called blue light, has a shorter wavelength than regular incandescent light. Many back-lit devices have a form of blue light which has been shown to suppress the release of melatonin, the sleep hormone. (1)
They found that the SHORTER the wavelength emitted by the electronic reading device, the LESS melatonin would be produced in the person reading. This resulted in delayed sleep onset and poorer quality of sleep. (1)
Here are the wavelengths of the e-readers measured in the study:
|Reading Device||Wavelengths in Nanometers|
|Kindle (original – not backlit)||612nm|
|iPad, iPad2, iPhone||452nm|
The Less Screen Time, The Better
Exposure to electromagnetic fields (EMFs) can also activate free radicals and a stress response in the body. (2) As if that weren’t enough, EMFs can disturb the body’s pineal melatonin production and disrupt its circadian rhythms. (3, 4) The pineal gland is situated in the middle of the brain and is the major site of the body’s melatonin production. Being exposed to blue light at night rapidly decreases both pineal melatonin production and blood melatonin levels, and nighttime reduction of melatonin has been shown to increase cells’ vulnerability to harmful carcinogens. (5, 6)
Research has shown that, in general, sleeping near electronic screens and more screen time are associated with shorter sleep durations. (7)
This science gives us tools to make informed, healthy decisions regarding how we read at night before bedtime, and how our choices can affect our sleep and ultimately our well-being. Choose wisely, and get your zzz’s for optimum health and vitality!