Do you use an electronic reading device before bed? More broadly, do you use your smart phone, a kindle, an iPad to browse or read through things before going to sleep? It wouldn’t be surprising if you do. These devices are entertaining and may get us through some boring periods of the day, but they certainly aren’t harmful to health, right? Logically, these devices should have some effect on our circadian rhythm, which is the internal clock that keeps us sleeping and waking at consistent and solid intervals. If your circadian rhythm is delayed, you may find yourself feeling tired later than usual. If you are someone who wakes up early to begin the day, going to sleep later is not a great idea. Since we know that bright light can push back the circadian rhythm, are these light-emitting devices affecting us when we are supposed to be getting sleepy? A recent study sheds some light on the answers to this question.
During this study, 12 individuals were assigned to two conditions: reading an E-book before bed or reading a standard paper book before bed. Each condition lasted for 5 days and was followed by a day of no reading and dim lights before bed. Each participant then participated in the other condition. During the 5th and final night of each condition, melatonin (which is a circadian rhythm marker) was measured. Additionally, sleep and wake times were measured on the 4th and 5th night of each condition. These factors were compared between E-book and standard book nights for each participant.
Results showed that melatonin levels were suppressed by up to 50% during the E-book condition. This is a bad thing, as melatonin is a sleep-promoting chemical! Additionally, sleep times were an average of 10 minutes later in the E-book condition than in the standard book condition. Nights of sleep in the E-book condition had significantly less REM sleep during the night. But does this affect quality of life? It certainly does. Although those who read the E-book reported feeling less sleepy in the evening, they reported feeling more sleepy in the morning.
The results of this study have enormous implications for everyday health. If you read or browse with any bright electronic devices before sleeping, it may be impacting your sleep and your quality of life. It is necessary to mention that the E-reader used was a standard device, and it was not equipped with super-bright lighting. This standard device was able to physiologically alter the circadian rhythm and its consequential effects. So although pushing sleep back by 10 minutes may not seem like a big deal, it becomes a big deal when you are unable to sleep in. This situation may lead to the accumulation of sleep debt. Given that those suffering from untreated (or even treated) sleep apnea are likely to have an increased amount of sleep disruptions, every 10 minutes per night counts!
Chang, A. M., Aeschbach, D., Duffy, J. F., & Czeisler, C. A. (2014). Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness. Proceedings of the National Academy of Sciences, 201418490.