Sunlight exposure does not just result in vitamin D production in our skin. It can also directly influence sleep quality through its effects on our circadian rhythms.[1] Increased exposure to sunlight in elderly nursing home residents can improve sleep quality scores.[2] Similarly, workers in windowless offices suffered from poorer sleep quality than those working by windows.[3] For workers in Antarctica in the winter,[4] the benefits of light can be produced using bright sun lamps, which make up for the negative effects of under-exposure of sunlight on sleep.[5] So, it seems that increased sun exposure could benefit sleep quality both through improved circadian rhythms and also increased vitamin D levels. Therefore, sun exposure is a confounding factor when studying the relationship between vitamin D levels and sleep.
References
- ^Wright KP Jr, McHill AW, Birks BR, Griffin BR, Rusterholz T, Chinoy EDEntrainment of the human circadian clock to the natural light-dark cycleCurr Biol.(2013 Aug 19)
- ^Düzgün G, Durmaz Akyol AEffect of Natural Sunlight on Sleep Problems and Sleep Quality of the Elderly Staying in the Nursing HomeHolist Nurs Pract.(2017 Sep/Oct)
- ^Boubekri M, Cheung IN, Reid KJ, Wang CH, Zee PCImpact of windows and daylight exposure on overall health and sleep quality of office workers: a case-control pilot studyJ Clin Sleep Med.(2014 Jun 15)
- ^Mottram V, Middleton B, Williams P, Arendt JThe impact of bright artificial white and 'blue-enriched' light on sleep and circadian phase during the polar winterJ Sleep Res.(2011 Mar)
- ^Smolensky MH, Sackett-Lundeen LL, Portaluppi FNocturnal light pollution and underexposure to daytime sunlight: Complementary mechanisms of circadian disruption and related diseasesChronobiol Int.(2015)