Sleeping Problems? The Impact of Light on Circadian Rhythm
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Today, let’s explore a major but often underestimated cause of sleep problems: light. Specifically, artificial light. Sleep disturbances have become a global health concern, and while various factors contribute, artificial light plays a significant role that often goes unnoticed.
Artificial light disrupts our circadian rhythm—our internal biological clock that regulates hormones, melatonin production, body temperature, and metabolism. Overexposure to light, particularly blue light emitted by screens and artificial lighting, can increase the risk of obesity, type 2 diabetes, and mental health disorders.
What makes this problem particularly insidious is how easily we overlook it in our daily lives. One stark example of its impact can be seen in hospitals, where constant exposure to artificial light has profound effects on patients. Let’s take a closer look at how disrupted circadian rhythms influence health outcomes.
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How Artificial Light Affects the Circadian Clock
It is well-established that exposure to blue light, particularly at night, disrupts the circadian rhythm and can lead to insomnia. Blue light (~480 nm wavelength) suppresses melatonin production, delaying sleep onset and altering sleep patterns.
Light is the most significant external cue for the circadian system. Throughout human evolution, the natural cycle of daylight and darkness has shaped our internal rhythms. However, the invention of electric lighting extended our waking hours, fundamentally changing how our bodies respond to the environment.
Artificial light not only influences our ability to see but also exerts non-visual effects on the brain, delaying the circadian phase, increasing alertness, and changing sleep architecture. These disruptions contribute to a range of health issues, including:
Depression and anxiety
Insomnia and poor cognitive performance
Metabolic disorders such as obesity and type 2 diabetes
Immune system impairment
Increased cancer risk
The primary pathway for these effects involves photosensitive retinal ganglion cells in the eye, which are particularly sensitive to blue light. These cells relay information to the circadian pacemaker in the hypothalamus, which regulates melatonin production and sleep timing.
Research has shown that mitigating exposure to blue light in the evening, such as by using blue-blocking glasses or dimming lights, can reduce melatonin suppression and improve sleep quality.