Most patients are familiar with the concept of circadian rhythm, with the topic usually rising in conversation around daylight saving time (or winter outside of the United States). However, many patients are not taking their circadian rhythm into account day to day. Explaining the effect of sunlight on internal sleep/wake cycles could help sleep professionals establish improved sleep hygiene with patients struggling to achieve a full night’s rest or experiencing trouble with their sleep schedule during the time changes.
Understanding the body’s sleep/wake cycles is an important part of establishing good sleep hygiene. For the sleep professional working to address sleep issues, supporting the patient in their understanding of potential causes of disrupted sleep or fatigue can be the first step toward determining if sleep hygiene is the root cause of the issue, or if there is an underlying sleep disorder needing identification and treatment. When speaking to the patient about their sleep hygiene habits, ask questions about their average sunlight exposure, and explain how natural light can impact the circadian clock year-round. The following information can provide support for explaining this relationship.
The Circadian Clock and Sunlight
According to the Centers for Disease Control and Prevention (CDC), the body’s circadian clock responds to the light/dark cycle of the sun to signal alertness and sleep. The body is most sensitive to light around an individual’s usual wake-up and bedtimes and throughout the night. By properly managing light exposure, patients could maintain a healthy sleep/wake cycle and improve their overall well-being.
Morning Wakefulness
If a patient is experiencing grogginess or trouble waking in the morning, they may be feeling the effects of cortisol, the body’s main stress hormone that spikes just after waking. Encouraging sun exposure within the first hour of usual wakeup times can help patients feel more alert and reduce stress. Increased sunlight exposure during morning hours can also improve sleep onset latency, particularly during the winter.
For patients who travel across time zones often, work remotely or have other barriers to morning sunlight exposure, a light therapy lamp — also known as a seasonal affective disorder (SAD) lamp — with dawn simulator features could help. However, it is important to note these lamps are not an exact replacement for natural sunlight, and sun exposure should be encouraged whenever possible.
Managing Sun Exposure Before Bedtime
A daily dose of sun can help promote restful sleep, with exposure during peak sunlight hours — morning and midday — being linked to maintaining a healthy circadian clock. This can be of particular importance during the winter months, when many patients see a decrease in natural light exposure and increase in sleep disruption. Allowing natural light to stream into the home can help the body establish a natural sleep/wake pattern — and save on utility costs.
Patients experiencing drowsiness too early in the day can benefit from spending time in a well-lit area, signaling to the body it’s not time to sleep yet. As regular bedtime hours approach, gradually dimming lights around the home to mimic a sunset — or simply using the fading natural light — can help the body wind down and prepare for a night of sleep. As part of establishing good sleep habits, encourage patients to keep bedrooms dark to avoid disruption of their circadian rhythm.
Conclusion
While natural light exposure is an important part of maintaining a healthy circadian clock, it can be an aspect of sleep hygiene practice that is overlooked by patients. Asking questions around a patient’s sunlight exposure habits can be helpful in understanding what may be impacting their sleep/wake cycles, and explaining the importance of sunlight to the body can help improve sleep hygiene and restful sleep.
The AAST Associate Editor