Review date
April 2023
Article publication date
February 2023
Summary
This cross-sectional study evaluated the association between sunlight exposure, changes in vitamin D levels and sleep quality. The study included 1,709 people from Brazil and was conducted between October and December 2020 during the Covid-19 pandemic. The study assessed sunlight exposure over one week and sleep quality using a questionnaire. Vitamin D levels were measured with a blood test. The authors reported that vitamin D levels were not associated with poor sleep quality (odds ratio (OR) 0.85; 95% confidence interval (CI) 0.43–1.72) among the people who received adequate sunlight exposure. However, vitamin D deficiency was associated with poor sleep quality (OR 2.02; 95% CI 1.10–3.71) among individuals with insufficient sunlight. They further reported that each 1-ng/mL increase in vitamin D levels reduced the chance of poor sleep quality by 4.2% (OR, 0.96; 95% CI 0.92–0.99). The study concluded that deficiency in vitamin D resulted in poor sleep quality among those who had insufficient exposure to sunlight.
Link to
Published in
Nutrition
Commentary by ARPANSA
The study has limitations that should be acknowledged, including the subjective nature of self-reported sleep quality and sun exposure, which may result in overestimation or underestimation of the findings. Previous studies have also concluded that sunlight and vitamin D can impact sleep quality. Studies by Boubekri et al (2014) and Mirzaei-Azandaryani et al (2022) reported that sunlight exposure and vitamin D supplementation could improve sleep quality in office workers. However, the relationship between sunlight, vitamin D, and sleep is complex and may be influenced by factors such as time of day, environment, and behaviour (Choi et al, 2020). Further research is needed to better understand this relationship.
The Cancer Council Australia mentions that most people reach adequate vitamin D levels through incidental sun exposure. When the UV index is above 3, adequate vitamin D levels can be maintained just by spending a few minutes outdoors. When the UV index is below 3, the Cancer Council Australia suggests adequate vitamin D levels can be still be reached by incidental exposure during outdoor physical activity or gardening. Despite Australia’s high solar UV, one in four Australians are estimated to be vitamin D deficient (Cancer Council Australia). The Cancer Council and the Endocrine Society of Australia recommend that people who may be at risk of vitamin D deficiency discuss their vitamin D requirements with their medical practitioner rather than seeking sun exposure.
