By Chang-Shanmei
What rituals do you repeat before bed? Do you lie down and continue watching a series or the latest videos from your YouTube subscriptions? Do you scroll through Facebook, LINE, and Instagram, liking friends’ posts and replying to messages? Or do you need a few rounds of an online game with friends before you can finally sleep?
Do Two or Three Hours Disappear While You Are in Bed?
After a busy day of classes or work, many of us want to relax. We lie down, take out a phone or tablet, and treat it as a reward at the end of the day. As mobile devices have become more capable, using them in bed has become a common habit and an emerging health concern.
Technology makes it easy to bring leisure into bed. We can find favorite topics on YouTube, follow new videos, choose films and dramas, read serialized comics, watch music videos, and keep up with celebrities. At the same time, notifications arrive from social platforms. We switch to Instagram or Facebook, reply to private messages, talk with friends, or play games. People with roommates may wear headphones, adding sound to the visual stimulation.
Light, Sound, and Stimulating Content Can Affect Sleep
Light, Sympathetic Arousal, and Melatonin
A 2018 study by Professor Sung-Jan Lin and colleagues at National Taiwan University reported that eight minutes of intense blue-light exposure produced sympathetic nervous system arousal in mice, including faster heart rate, higher blood pressure, and sweating. The response lasted for more than an hour after the light exposure ended.
Some studies suggest that blue light from phones, tablets, and computers can suppress melatonin, delay the circadian clock, and make it harder to feel alert the following morning. The evidence is not entirely consistent. One reason is that humans were exposed to artificial lighting long before smartphones appeared. Energy-efficient LED lighting can also contain wavelengths toward the blue portion of the spectrum.
Over recent decades, average sleep duration and sleep quality have declined, with consequences for health. A 2014 study of 1,508 American adults found that 90 percent used a phone or tablet during the hour before bed. In an experimental comparison, participants who read an e-book before bedtime took longer to fall asleep, produced less melatonin, and felt less alert the next morning than those who read a printed book.
Melatonin and Serotonin: Important for Sleep and Emotional Well-Being
Melatonin regulates the circadian rhythm and helps the body prepare for sleep. Light-sensitive cells in the retina convey environmental light patterns to the brain’s suprachiasmatic nucleus, influencing melatonin production. Daylight also supports the production of serotonin, which is involved in emotional stability and is one of the substances used to synthesize melatonin.
Retinal ganglion cells respond to environmental brightness and help signal darkness to the pineal gland. Melatonin is therefore sometimes called the “hormone of darkness.” It is highest at night and gradually declines as morning approaches. Light is one of the strongest influences on its release.
Longer use of light-emitting devices before bed can increase alertness, delay sleep, suppress melatonin, shorten sleep duration, and delay rapid eye movement sleep. Feeling unrefreshed the next morning may lead people to use caffeine, creating a cycle that further disrupts sleep.
Some people spend nearly all day under artificial lighting. Try to go outdoors before noon for at least 30 minutes of activity or exercise, or spend more than an hour in an environment with natural light. Daylight helps the body become alert during the day and supports serotonin production, providing the body with what it needs to produce melatonin at night.
How Can We Sleep Better?
If you often have trouble falling asleep, staying asleep, or feeling rested, try these eight habits:
- Spend at least 30 minutes exercising or being active outdoors after sunrise and before noon.
- Reduce caffeinated drinks.
- Avoid electronic devices during the two hours before bedtime whenever possible.
- Do not bring phones or tablets into bed.
- Turn off platform notifications and reconsider unnecessary subscriptions.
- Prepare a bedroom suitable for rest, including sufficiently dark lighting.
- End the day’s work before bedtime. Write unfinished tasks down and give them to your future self.
- If you must use a phone in bed, shorten the time and keep a room light on rather than staring at the screen in complete darkness.
Bedtime phone use can also contribute to neck strain, poor posture, and eye problems. If sleep difficulties continue after changing these conditions, or if you frequently experience difficulty falling asleep, light sleep, or early awakening, consider an evaluation at a sleep medicine center or by a mental health professional. Identifying the underlying problem is the first step toward treating a sleep disorder.
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