Effects of Artificial Light on Sleep and Circadian Rhythm

Introduction

Light greatly impacts one’s sleep, being the most significant external factor. While it is commonly understood that sleeping in darkness is easier, the connection between light and sleep runs deeper. Light is crucial in regulating the body's internal clock, known as the circadian rhythm, which determines when one should be awake and rest. It also influences the production of melatonin, a hormone essential for promoting sleep. Daily exposure to light, including its type, timing, and duration, significantly affects sleep patterns. Understanding the intricate relationship between light and sleep can help arrange the bedroom to promote consistent, high-quality sleep.

How Does Artificial Light at Night Affect Sleep and Circadian Rhythms?

Although human bodies are naturally attuned to sleep according to the natural cycle of day and night, the widespread availability of electricity enables constant illumination regardless of time. This means artificial light, found in streetlights, office spaces, and electronic devices like cell phones, plays a significant role in modern life, impacting one’s sleep patterns, biological clock (circadian rhythm), the production of melatonin (a hormone crucial for sleep), and overall sleep quality.

Circadian rhythms are like the body's built-in clock, controlling various functions, including sleep over a 24-hour cycle. This internal clock, managed by a part of the brain, is highly sensitive to light. When light enters the eyes, it tells the brain what time it is, guiding the body's activities accordingly. Natural light helps the body stay in sync, alerting one during the day and sleepy at night. However, modern life's abundance of artificial light can disrupt this rhythm.

Too much artificial light at the wrong times can confuse one’s internal clock, messing up the sleep patterns. This disruption does not just affect sleep; it can also lead to problems like weight gain, heart issues, and possibly even cancer. Circadian rhythms also play a big role in mood, mental health, and seasonal affective disorder.

What Are Cardiac Rhythm Disorders?

Circadian rhythm disorders happen when the body's internal clock is not synced with the surroundings. Light exposure plays a big role in many of these disorders.

• Jet Lag: Jet lag occurs when traveling across different time zones messes up the internal clock. This can make it hard to sleep when one wants to or feel tired during the day. To fix it, one needs to adjust to the new time zone by getting sunlight at certain times and avoiding light at others. This adjustment can take a few days to a couple of weeks.

• Shift Work Disorder: Some jobs require working late into the night or overnight, which can mess up the internal clock. This disorder makes it hard to get enough sleep and can lead to feeling sleepy when one should be awake. It also increases the risk of accidents at work.

• Other Circadian Sleep-Wake Disorders: Sometimes, the internal clock gets out of sync, causing problems with sleep timing. This can be due to one’s daily habits and exposure to light.

Treatment often involves light therapy, where one sits close to a bright lamp that mimics sunlight at specific times to help reset the internal clock.

Which Kinds of Light Influence Sleep?

Various types of light impact sleep differently. Daylight, with its high illuminance reaching up to 10,000 lux, greatly influences sleep patterns due to its intensity compared to indoor lighting, which typically maxes out around 500 lux. Artificial light also varies in its effects, with differences in illuminance and brightness. Even lights appearing equally bright can differ in wavelength, affecting how they affect eyes and brain.

For instance, blue light, emitted by many LEDs and common in electronic devices like phones and tablets, has a short wavelength. Research suggests it significantly disrupts melatonin levels and circadian rhythms more than longer-wavelength light. Excessive exposure to blue light from such devices, especially in the evening, can contribute to sleep disturbances.

Is It Better to Sleep in Total Darkness?

Generally, it is recommended to sleep in complete darkness as much as possible. This minimizes distractions and helps maintain uninterrupted sleep. Sleeping with a light on can disrupt sleep patterns, leading to more fragmented rest, especially in the hours just before waking up. Studies show that simply closing the eyes is insufficient to block out light. Even small amounts of indoor light can affect the body's internal clock, even when the eyes are shut. Besides improving sleep quality, there are other reasons why it is advised to sleep in total darkness:

• Eye Comfort: Even faint light during sleep can strain the eyes, causing discomfort, tiredness, and difficulty focusing.

• Weight Management: Sleeping with lights on may disrupt the body's natural metabolism rhythms, potentially increasing the risk of weight gain over time.

• Cancer Risk: Some studies have found a link between high levels of artificial light at night in homes and increased risks of certain cancers, like breast and prostate cancer. However, more research is needed to confirm this connection.

These potential effects of excess artificial light underscore its impact on the body's internal clock and overall health.

How to Create the Ideal Sleep Environment in the Bedroom?

Start by making the bedroom as dark as possible. Use blackout curtains to block out external light and create a darker space. Before bedtime, keep the lights dim. A small, low-power lamp can help ease into bedtime without bright lights. Dim lighting with a warm color can help people relax and prepare for sleep.

Limit or avoid bringing technology into the bedroom. Screens can keep the brain active, making it harder to fall asleep, and the light they emit can disrupt the body's sleep cycle. If one must have electronics in their room, dim the brightness, avoid using them right before bed, and keep them silent during the night.

• Using an Eye Mask: If someone else insists on keeping a light or the TV on in the bedroom, compromising sleep, try discussing the importance of darkness for quality rest. If they still prefer to keep some light, ensure it is at the lowest setting possible. If the light remains bothersome, wearing a snug-fitting eye mask can help. Some studies suggest that using an eye mask can improve sleep quality.

• Adjusting Electronics Settings: If one falls asleep with the TV on, it emits artificial light throughout the night, disrupting sleep. Ideally, remove the TV from the bedroom. If not feasible, check if the TV has a sleep timer to switch it off after a set time automatically. Alternatively, establish a nightly "lights out" time to consistently turn off the TV.

Similarly, limit screen time on cell phones before bed. Consider using glasses that filter blue light or activate "night mode" on the devices to reduce blue light emission. Several apps are also available to help reduce blue light.

Conclusion

The pervasive presence of artificial light, particularly at night, significantly impacts sleep quality and circadian rhythms. Exposure to artificial light disrupts the body's internal clock, affecting the production of melatonin and leading to sleep disturbances. Circadian rhythm disorders such as jet lag and shift work disorder highlight the importance of balancing natural and artificial light exposure. Creating a bedroom environment conducive to quality sleep, with measures like blackout curtains, dimming lights, and limiting technology, is crucial for mitigating the negative effects of artificial light on one’s health and well-being.