Many factors can impact our sleep: noise, too much caffeine, and eating right before bed. But did you know that light exposure is another major factor that can prevent you from restful sleep? Light is the most significant environmental factor that affects sleep. Though this may seem obvious because we sleep when it’s dark and are awake during daylight, the relationship between light and the systems that sustain our body is more deeply connected than you may think.
We are exposed to artificial light now more than ever, especially with the range of devices (smartphone, laptops, iPad, etc.) that are integrated into our daily lives. This light exposure and the length of time we are exposed to it critically affects sleep by impacting the circadian rhythms as well as melatonin production and sleep cycles. Learning about how light impacts sleep and the adjustments you can make can help you achieve quality sleep consistently.
Light and the Circadian Rhythm
The body’s circadian rhythm is an internal 24-hour clock that guides several of the body’s natural processes including appetite, mood, and sleep. The circadian rhythm is managed by the circadian pacemaker which is an area of the brain that receives its signals from light exposure. When the eyes are exposed to and absorb light, cells in the eyes send information about the time of day to the brain. The brain interprets this information and sends signals throughout the body which informs when functions are carried out. So circadian rhythms are cycles in the body that happen in 24 hours and are informed by light exposure. These 24-hour patterns the body and brain cycle through include the sleep-wake cycle (we are awake during the day and asleep at night), body temperature, hunger, and digestion.
In today’s society, there is an abundance of light sources that can impact and alter the circadian rhythm. So rather than only being exposed to natural light and the circadian rhythm being guided by sunset and sunrise, other light sources affect the brain’s circadian pacemaker. Even short periods of exposure to artificial light can cause a person’s circadian rhythm to change and become misaligned with the regular sleep-wake cycle that corresponds to natural daylight. Artificial light exposure that happens later in the evening can push back the sleep cycle, meaning that people go to bed later. This can contribute to health risks including issues with metabolism, sleep disorders, and seasonal affective disorder.
Impact of Light on Melatonin and Sleep Cycles
In addition to altering the circadian rhythm, light exposure can also affect the production of melatonin and sleep cycles. Melatonin is a hormone produced by the pineal gland which is in the brain. This hormone is critical to regulating sleep as it tells the body when to sleep and wake. Increasing levels of melatonin produce tiredness which facilitates sleep. Light exposure guides the production of melatonin – more is produced at night after the sunsets. So greater exposure to artificial light in the evening can reduce levels of melatonin, preventing restful sleep.
Light can also disrupt sleep cycles. During one night of normal sleep, an individual experiences 4-6 sleep cycles. Each cycle consists of several sleep stages that last an average of 90 minutes, each progressively entering into a deeper sleep. These stages and cycles of sleep are critical for the body’s systems to replenish. Excess light exposure can disrupt these stages, interrupting sleep. This reduces the amount of time in deeper sleep stages which impacts overall sleep.
Tips to Get the Best Sleep
There are various ways you can reduce unhealthy light exposure and promote healthy sleep. A few tips you can integrate include:
- Adjust environmental light: in the evening, use low illuminated lights that have a warmer color. Keep the lights dim as you transition to bed and avoid having excess lights/lamps on. Try using black-out curtains to make your space as dark as possible.
- Reduce technology use: reduce screen time on electronic devices before bed. Screen time can keep the mind overly active which delays going to sleep and the light can affect your circadian rhythm. Turn the brightness down on your devices and avoid the screen one hour before sleeping.
Making these adjustments can enhance your sleep quality. The benefits of restful and restorative sleep are numerous: increases energy, boosts mood, and replenishes the body; helping you be prepared for the following day!