Expert Science Popularization – Phototherapy for Treating Insomnia
Light is everywhere. Have you ever thought that light can also be used as a treatment for insomnia? How does light affect sleep? What are the indications for phototherapy? Today, let’s talk about it in detail.
1、 Light and Sleep
How does light affect sleep?
(1) One of the mixtures most affected by light: serotonin
Serotonin is beneficial for generating happiness and well-being, and is very important for regulating the internal biological clock of the human body. A study on the sleep quality of day shift office workers showed that compared to those who directly rely on windows, those who do not rely on windows receive 173% less natural light and sleep an average of 46 minutes less per night.
(2) The secretion of melatonin is closely related to sunlight exposure
When the environment darkens, the pineal gland naturally secretes melatonin. Morning sunlight can inhibit the secretion of melatonin. If one stays in a strong light environment such as a convenience store for a long time at night, it will hinder the secretion of melatonin, leading to disturbances in sleep and body rhythm.
(3) Cortisol and melatonin are a pair of hormones that are inversely correlated
Cortisol levels increase, melatonin levels decrease; When melatonin levels increase, cortisol levels decrease. Promoting the correct hormone production at the right time will automatically promote the normal operation of other hormones. Exposure to sunlight during the day can stimulate the production of cortisol, allowing us to actively obtain food and work with mental satisfaction.
2、 Working principle
By interacting with retinal ganglion cells, it affects the hypothalamic suprachiasmatic nucleus that controls circadian rhythms and inhibits melatonin secretion from the pineal gland. The sleep wake state of humans is generated by the interaction between endogenous circadian rhythms and the state of sleep itself. When the sleep time is consistent with the endogenous circadian rhythm, the best sleep quality can be achieved; And when this balance is disrupted, it may lead to insomnia or drowsiness.
Based on this principle, phototherapy can improve sleep quality, increase sleep efficiency, and prolong sleep time by helping to establish and consolidate regular sleep wake cycles. Light therapy for circadian rhythm sleep disorders mainly relies on the duration of light exposure, such as a period of time after waking up or before going to bed. Light exposure in the evening generally causes a delay in biological rhythms, while light exposure in the morning advances the circadian rhythm.
3、 Therapeutic effect
The effectiveness of phototherapy is closely related to the nature of the light source, light intensity, and duration of irradiation.
(1) Divided by the nature of the light source: natural light, artificial light
Natural light may vary due to unpredictable factors such as sunny and rainy days, but phototherapy equipment can maintain continuity and consistency in lighting. In addition, compared to long wave light, visible light short waves such as blue light (460nm) are more effective in resetting circadian rhythms and improving sleep disorders.
(2) Light intensity: 2500~10000 lux
Research has consistently found that exposure to artificial light ranging from 2500 to 10000 lux for phototherapy can improve sleep wake quality and mood. The outdoor light intensity measured at dusk or dawn on a sunny day is similar to the intensity of artificial light generated by many phototherapy devices (approximately 10000 lux). Therefore, for insomnia patients who have difficulty falling asleep, it is beneficial to take a morning walk immediately after waking up.
(3) Duration of irradiation: 30-45 minutes/day
To ensure patient compliance, the duration of light exposure should be relatively short (<2 hours), generally 30-45 minutes per day.
Current research shows that phototherapy has significant therapeutic effects in treating diseases such as circadian rhythm disorders, non seasonal depression, bipolar disorder, and sleep disorders in patients with Parkinson’s syndrome/Alzheimer’s disease. A meta-analysis summary: Phototherapy is effective in treating insomnia, and its therapeutic effect on insomnia is greater than other sleep disorders, even surpassing its effect on circadian rhythm sleep disorders.
4、 Warm reminder
The possible side effects of phototherapy include headache, nausea, dry mouth, eye fatigue, discomfort for people with existing retinal lesions and those who use photosensitive drugs, and may also induce mild mania. This can be avoided through the following methods:
① Reduce the dose of light (intensity, duration, or both);
② Increase the distance of the light source;
③ Adjust the lighting time;
Summary
Phototherapy is a natural, simple, and low-cost treatment method that does not cause residual effects or tolerance. It can improve mood, sleep wake quality, and help establish and consolidate regular sleep wake cycles.
At present, it is recommended to combine phototherapy with medication or other treatment methods to treat insomnia disorders. If you are suffering from insomnia, especially those with jet lag insomnia or difficulty falling asleep, you can try phototherapy.