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Blue Light and Sleep

Dr. Hanesh Patel

Blue Light and Sleep

The human internal sleep cycle, or circadian rhythm, is controlled by melatonin, a hormone, that is released into the body from the Pineal gland. Melatonin release is dependent on multiple factors, one of which is light entering the eye and triggering the melanopsin photoreceptor to signal the suppression of melatonin.

Traditionally, sunlight controlled the body’s melatonin levels. During the day, light from the sun inhibits melatonin secretion and signals the body to be awake. Once the sun sets and the light decreases, melatonin is released, and the body prepares for rest. That being said, if the body continues to be near artificial light sources, it can affect the body’s ability to rest.

Light Spectrum Graph

Figure 1: Light spectrum showing high-energy visible light

Blue light (or High Energy Visible light) is defined as the shortest wavelengths in the visible electromagnetic spectrum, specifically 400-500nms. Light has always been an important aspect of human lives. Early humans lit fires to provide light in the evenings, and from there, lamplight and then incandescent bulbs were used, all of which have low amounts of blue light. In the 1930s fluorescent lighting was introduced which increased blue light exposure, however these light sources were typically used in commercial and industrial applications, therefore evening exposure was limited. Studies have shown that the melanopsin photoreceptor is most sensitive to 470nm light, therefore blue light plays the most significant role in the suppression of melatonin release.

Spectral Light Graph

Figure: Spectral distribution of various light sources. Note that cool white LED emits levels of blue light which mimic the amounts in daylight.
Source: Smick, K et al. Blue Light Hazard: New Knowledge, New Approaches to Maintaining Ocular Health.

With the advent and proliferation of LED light sources our exposure to blue light has increased dramatically. With this increase many people are using digital, LED-lit, screens later in the evening and until their bedtime. This exposure to blue light late into the evening reduces melatonin production, inhibits sleep and increases the circadian rhythm length. Over time, this can lead to issues with falling asleep and create poorer quality of sleep which may be linked to the causation of cancer, diabetes, heart disease and obesity.

Research has shown that melatonin secretion can occur by reducing blue light exposure, which will allow the body to regulate sleep. Various solutions exist to limit light and blue light exposure in the evenings. For example, many eyeglass lens manufacturers now incorporate blue-light filtering or reflecting technology into their optical solutions. Wearing blue-light filtering lenses in the evening has been shown to double melatonin levels compared to direct exposure to LED light sources.

Light intensity and blue-light can also be reduced at the source. Many smartphone manufacturers utilize a form of “night mode” to minimize blue-light emission. LED video monitors which incorporate technology to control brightness of the screen and blue-light emitted have been developed in order to reduce the effects of exposure on the user. BenQ, a global leader in display technology, has created eye-care technology that is utilized in all of their monitors to reduce blue light, adjust brightness automatically based on ambient lighting and remove LCD screen flicker for a healthier viewing experience. Their Low Blue Light technology specifically filters out hazardous blue light to reduce eye fatigue and irritation, particularly when viewing the screens in the evening.

Reducing blue light, particularly in the evening hours, can play a big role in living a healthy lifestyle. Utilizing technology like BenQ’s monitors or even blue light reducing eyeglasses can help promote your sleep cycle and regulate your melatonin secretion.

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