By Jane Yang 楊靜悠 In our modern, hyper-connected world, smartphones have become ubiquitous companions for many of us. However, the convenience and allure of these devices may come at a cost, particularly when it comes to our sleep habits. Do you find yourself habitually reaching for your smartphone as you wind down for the night, only to find yourself hours later still scrolling through endless social media feeds or watching video after video? If so, you're not alone. Let’s explore the impact of bedtime smartphone use on our circadian rhythms — the body's internal clock that controls our sleep-and-wake cycles. Toward the end, we will provide some insights on how to regain a restful sleep. Blue Light from Electronic Screens Modern electronic screens, from smartphones to computer monitors, utilize the RGB color model to display a wide range of hues. This method relies on mixing varying intensities of the three primary colors — red, green, and blue. However, what many don't realize is that blue light has a profound impact on our circadian rhythms [1, 2]. Melatonin-Suppressing Effect of Blue Light Our body’s biological clock needs to be calibrated every day, so that our behavior and physiology can optimally adapt to the external day-night cycle [3]. Sunlight is composed of light waves of all the visible colors, of which retinal ganglion cells have been shown to play a key role in detecting blue light to synchronize our circadian rhythms [4]. Retinal ganglion cells are photoreceptors that do not contribute to our visual perception. However, in response to blue light, they will send signals to the suprachiasmatic nucleus (SCN) — a structure located in the anterior part of the hypothalamus [5] — to tell the brain that it is daytime. The SCN then regulates the release of melatonin by the pineal gland — stimulation in darkness and suppression in light — to modulate internal biological events, such as sleep-wake cycles and some energy metabolism functions (e.g. glycogen synthesis and daily phase of high insulin sensitivity) [6]. The blue light exposure in the evening hours, therefore, confuses our brain and disrupts our sleep-wake cycles, making us difficult to fall asleep. The mechanism by which blue light from electronic screens disrupts our circadian rhythms is similar to jet lag. When we traverse multiple time zones, our internal clocks struggle to immediately adjust to the new daylight pattern of the destination. This mismatch between our body's internal clock and the local time confuses our body, leading to symptoms like fatigue and difficulty sleeping. How to Regain Your Sleep from Your Smartphone? 如何從智能手機 搶回睡眠時間？
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