Why is bright light at night bad for sleep?

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Bright light at night is detrimental to sleep for several reasons:

  1. Melatonin Suppression: Bright light exposure, especially between 10:00 p.m. and 4:00 a.m., can significantly reduce melatonin levels, a hormone crucial for sleep onset and maintenance. Melatonin makes you feel sleepy, and its suppression by light can interfere with your ability to fall asleep and stay asleep 1 2.

  2. Circadian Rhythm Disruption: Our sensitivity to light changes throughout the day. While we need high photon energy in the morning to set our circadian clock, very little light at night can shift this clock, disrupting sleep patterns. Exposure to bright light at the wrong time can misalign your internal body clock, leading to poorer sleep quality 3.

    Optimizing Sleep Light

    Melatonin is crucial for sleep, and exposure to bright artificial lights at night can disrupt its release. To enhance sleep quality, dim lights in the evening and embrace low-level lighting, similar to practices in Scandinavian cultures. Viewing natural light during the late afternoon can help counteract some negative effects of artificial light exposure at night.
    Huberman Lab
    Sleep Toolkit: Tools for Optimizing Sleep & Sleep-Wake Timing | Huberman Lab Podcast #84
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  3. Activation of Wake-Promoting Neurons: The neurons that respond to light and help wake you up are located in the lower part of the retina, which gets stimulated primarily by overhead light. Exposure to overhead artificial lights at night mimics sunlight, signaling to your brain that it should stay awake, which is counterproductive for sleep 1.

  4. Mood and Mental Health Effects: Bright light exposure at night can suppress dopamine release, a neurotransmitter associated with mood and motivation. This can negatively affect mental health, worsening issues like depression and anxiety. Consistent exposure to light at night can also impair learning and increase susceptibility to certain metabolic issues 4 5.

  5. Improper Light Management: Lowering light exposure in the evening, using dim lights or red lights, can help signal to your brain that it's time to prepare for sleep. Contrarily, bright lights in the evening can trick your brain into thinking it's still daytime, hence delaying sleep onset 6.

It is advisable to dim lights and use minimal lighting during these critical hours to enhance sleep quality and maintain a healthy circadian rhythm.

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red light

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Red light has several benefits, particularly when it comes to improving sleep quality and overall health.

Sleep and Circadian Rhythm

  • Melatonin Production: Red light, particularly when dim, does not inhibit melatonin production, making it an ideal light source for the evening and night. It allows you to stay awake if needed without disrupting your sleep rhythm 1.
  • Reduced Cortisol: Using red light helps lower cortisol levels at night, aiding in better sleep transitions and improved sleep quality overall. It is beneficial for maintaining low evening cortisol and improving the transition to sleep 2.

Health Benefits

  • Photophobia and Headaches: Red light can be helpful for people experiencing photophobia, as it minimizes discomfort and may prevent headaches triggered by bright light. Simple, inexpensive red lights can be used to continue daily activities without the adverse effects of brighter lights 2.
  • General Health: Red and near-infrared light improve several aspects of cellular and organ health, including faster muscle recovery, improved skin health, wound healing, acne reduction, decreased pain and inflammation, enhanced mitochondrial function, and even better vision 3.

    Red Light Benefits

    Andrew explains how red light can improve neuronal function when used early in the day, and can also be beneficial for shift workers who need to stay awake at night. Red light, if sufficiently dim, does not inhibit melatonin production or increase cortisol at night, making it the preferred light source for those who need to work late.
    Huberman Lab
    Using Light (Sunlight, Blue Light & Red Light) to Optimize Health | Huberman Lab Podcast #68
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Practical Use

  • Evening Routine: Switching to red lights an hour before bed can help induce sleepiness and improve overall sleep quality. Dim red lights, such as those from brands like Joov or Bond Charge, are effective for this purpose. Commercial red light products should be used early in the day for benefits like improved mitochondrial function 4 5.

In summary, red light is beneficial for maintaining sleep quality by not disrupting melatonin production and lowering cortisol levels in the evening. It also supports various health improvements, making it a versatile tool for both evening relaxation and general wellness.

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