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The Effects of Sun Exposure on Sleep Duration

Getting enough high-quality sleep each night is vital for good health[1] and longevity[2]. Although general recommendations vary by age[3], most experts agree that the average adult needs between seven and nine hours per night. Various factors impact sleep quality, including sleep disorders[4], disturbances and diet. Fortunately, there are several steps individuals can take to improve their overall sleep hygiene[5], including tracking sleep patterns, organizing the bedroom and using sleep apps[6].

Links also exist between sunlight and sleep[7], with light exposure beneficial for restorative sleep. Being outdoors and soaking up natural light also promotes mental health[8], which, in turn, can aid sound sleep. Indeed, poor sleep can exacerbate mental health[9] conditions and vice versa, creating a cycle that can be tough to break. Getting plenty of light exposure can be challenging during winter when daylight hours are shorter and cold temperatures keep people indoors. This article covers why and how people should spend time in the sunshine for a better night's rest.

Sunlight and Vitamin D

Often referred to as the "sunlight vitamin"[10], vitamin D is vital for strong bones, nerve and muscle function, regulation of blood sugar and a healthy immune system[11]. Studies also show that it can help regulate sleep[12]. Indeed, a vitamin D deficiency[13] can negatively impact sleep quality.

Although limited foods[14] contain vitamin D, one of the easiest ways to increase levels is to bask in the sun's rays. Supplements[15] are also available, working in the opposite way to melatonin[16] — the sleep hormone. However, research indicates that taking vitamin D supplements too late in the day can have the unwanted effect of worsening insomnia[17].

Sunlight and the Circadian Rhythm

Natural light helps the body to regulate its internal clock — the sleep-wake circadian rhythm[18]. This natural cycle is vital for human functioning. Although several aspects can boost or maintain a healthy rhythm, such as exercise[19], limiting daytime naps and sticking to sleep schedules, light is among the most important factors[20]. That said, artificial light in the evening[21] can disrupt the body's natural cycle, while daytime sunlight, particularly in the morning, can increase wakefulness during the day and sleepiness at night. Additionally, daytime sun exposure can help the body remain asleep throughout the night for high-quality rest.

How to Get More Sunlight

Simply spending time outdoors may seem like the most obvious way to increase sun exposure, but cloud cover and smog[22] can block the beneficial rays, particularly when it comes to getting vitamin D. People should try and head outside for a stroll when the sun is actually shining. Moreover, exercising in the sunshine can support the circadian rhythm even further. Heading outside[23] as often as possible, such as a lunchtime walk outside the office, increases an individual's exposure to the sun. Sometimes, however, enjoying much sunlight during the winter can be impossible. Physicians may recommend light therapy[24]. Alternatively, a winter vacation to sunnier climes could be valuable!

In short, whatever way you do it, increasing your natural light exposure over the winter months is sure to benefit your all-around health, mood, and sleep.


  1. National Heart, Lung, and Blood Institute – Why Is Sleep Important?
  2. SoClean – New Research: Sleep Well to Live Longer
  3. National Heart, Lung, and Blood Institute – How Much Sleep Is Enough?
  4. Cleveland Clinic – Sleep Disorders
  5. SoClean – Everything You Need to Know About Sleep Hygiene
  6. SoClean – Top Sleep Apps for Improving Your Zzzs
  7. National Library of Medicine – Relationship between Sleep Duration, Sun Exposure, and Serum 25-Hydroxyvitamin D Status: A Cross-sectional Study
  8. National Library of Medicine – Association Between Sunlight Exposure and Mental Health: Evidence from a Special Population Without Sunlight in Work
  9. Harvard Health Publishing – Sleep and mental health
  10. National Library of Medicine – Sunlight and Vitamin D
  11. National Institutes of Health – Vitamin D
  12. National Library of Medicine – Vitamin D and Sleep Regulation: Is there a Role for Vitamin D?
  13. University of Nebraska-Lincoln – 9 vitamin D deficiency symptoms (and 10 high vitamin D foods)
  14. Healthline – 7 Nutritious Foods That Are High in Vitamin D
  15. National Library of Medicine – Vitamin D Supplementation and Sleep: A Systematic Review and Meta-Analysis of Intervention Studies
  16. National Center for Complementary and Integrative Health – Melatonin: What You Need To Know
  17. MedicalNewsToday – Can vitamins cause insomnia?
  18. National Library of Medicine – Physiology, Circadian Rhythm
  19. National Library of Medicine – Circadian Rhythm, Exercise, and Heart
  20. National Heart, Lung, and Blood Institute – Circadian Rhythm Disorders Treatment
  21. National Library of Medicine - Effects of light on human circadian rhythms, sleep and mood
  22. Healthnews – Are You Getting Enough Sun to Make Vitamin D?
  23. WebMD – Summer Sun for Winter Blues
  24. Harvard Health Publishing - Light therapy: Not just for seasonal depression?