As presented in Light regulates our internal clock and Synchrony of circadian rhythm for healthy sleep, the photic (light) information that is captured by our eyes helps regulate our internal body clock within the brain. Specifically, the cells in our eyes that communicate directly to this part of the brain respond to general levels of brightness of our environment, but also have a stronger sensitivity to the blue light spectrum.
By using the light/dark cycle of the environment, our bodies are regulated to be awake during the day time and asleep during the night. However, this rhythmic exposure can easily get trumped with modern day lighting and technology.
Therefore, maintaining a natural light/dark rhythm during the morning, day, evening and night will help promote our body’s natural rhythm and make it easier transition to a sleep state.
Reducing light exposure in the evening is one of the key steps in promoting sleep. Specifically, light interferes with the secretion of melatonin, our natural ‘night-time’ hormone that indicates to the body and brain that it is night-time and, therefore, sleep time. Reduced levels of melatonin are associated with delayed sleep onset – a harder time to fall asleep – as well as an overall lower quality of sleep throughout the night.
The following section provides advice on how to reduce exposure to lights come evening fall.
Reduce light exposure in the evening
To support the transition into our sleep state, in the hour or two before desired bedtime, it is important to reduce environmental lighting conditions. Reduce brightness levels by switching to lamp lighting or, if possible, optimize the use of dimmers throughout the house.
In addition to reducing overall brightness levels come evening time, it can also be beneficial to be weary of the type of lighting used. As shown in the figure below, the proportion of different colours emitted (wavelength spectrum) varies per light source.
Importantly, using ‘warmer’ lighting options is beneficial for evening time lighting as these type of lightbulbs emit a smaller amount in the blue light spectrum, causing less interference with our body’s secretion of melatonin in the evening.
In our own house, we switched to 3000K LED lights (warm white) throughout the house with the exception of the kitchen. This makes for makes for a more alerting environment where needed (i.e. kitchen) but a more relaxed ambiance in rooms where we spend most evenings, including the dinning room, living room and bedroom.
Additionally, our bathroom and bedroom are also equipped with dimmers to lower light intensity when getting ready to go to bed. As a bonus, I personally find that dimmers or, alternatively, the use of a nightlight in the bathroom also avoids the problem of blinding light when needing to use the bathroom a night.
Reduce exposure to electronics
Electronics are a particular area of concern come evening time. Although we all enjoy some relaxing time in front of the tv, watching a movie, or on our phones scrolling through social media, exposure to these screens can have devastating effects on our ability to fall asleep.
Cell phones, tablets and laptops are particularly disruptive when it comes to good quality sleep. The light emitted is not only strong, but is also directed towards you and typically from a close distance.
Televisions have been shown to be less worrisome as they are generally viewed at a farther distance and, depending on the type of TV, emit light at a relatively lower brightness level compared to other electronic devices.
I myself noticed a difference in the time to fall asleep when I play around on my cellphone, or watch Netflix on my tablet before bed.
Interestingly, recent studies have shown that the effects of screen time in the hour before bed may be enhanced when these are used in darkness, when ambient lighting is turned off. I know quite a few people tend to go to bed, turn off the lights and play on their phone or scroll through social media before falling asleep. These early results suggests that although lower quality sleep is observed with general use of electronic devices before bed time, environmental brightness, such as whether you are in a lit or darkened room when using these devices, can also play a factor. Specifically, when in a darkened environment, your pupils will dilate as a natural response to allow more light to enter the eye. The use of electronic devices in the absence of ambient light will therefore result in that the brightness of the screen will have a more pronounced effect, both on eye strain as well as on the quality of your sleep.
Good practice would be to avoid use of electronic devices in the hour or two before falling asleep. This time can instead be used to reinforce a relaxing bedtime routine (see Pre-bed ritual: Relax the mind and Pre-bed ritual: Relax the body). If electronic devices must be used, adjust settings to lower the screens brightness. Most cellphone and tablet, and even laptop nowadays come with auto-adjust brightness settings and night-time mode.
In addition to decreasing the overall brightness emitted by the screen, it can also be beneficial to reduce the level of blue light emitted from them. Back in my graduate study days, I would often find myself in front of my computer in the evening and before bed. Apps such as f.lux (https://justgetflux.com/) have an automatic adjustor at set times, or follow sunset and sunrise to reduce the level of blue light emitted and turning the screen to a soft orange.
We all know that technology has many perks and advantages and is often used to relax at the end of the day. However, it is important to be weary of how both ambient lighting and the use of electronic devices in the evening can affect our sleep by disrupting our circadian rhythm, including the production of melatonin, our night-time hormone. By reducing light exposure in the evening, our bodies will be able follow their natural pattern to transition from wake to sleep.
Mireku, M. O., Barker, M. M., Mutz, J., Dumontheil, I., Thomas, M. S., Röösli, M., … & Toledano, M. B. (2019). Night-time screen-based media device use and adolescents’ sleep and health-related quality of life. Environment international, 124, 66-78.