This paper is an overview of studies on the effects of daylight exposure on human health.
The purpose of this paper is to present current evidence of how daylight impacts human health and to discuss the relevance of the resulting information to construction and renovation projects.
Studies to be included in the review were first identified through a two-step literature search. The first step involved searching PubMed and Scopus databases using keywords such as ‘daylight’, ‘sunlight’, ‘natural light’, ‘health’, and ‘human’. Secondly, searches were performed using specific health terms. Studies of daylight effects on human health were included and a pre-selection process was used based on the journal title or topic to narrow the search. Data extracted from the included studies included as many of the following elements as were available: studied health effects, light source, illuminance, time or duration of exposure, number of subjects, statistical evidence, and conclusions related to daylight and health.
Eighteen unique studies met the eligibility criteria for further analysis. One article reported the best sleep timing, duration, efficiency, and quality under natural light conditions; four studies focused on the relationship between daylight hours and physical activity; one article used daylight hours to study the effect on myocardial infarction; one article researched the season of birth with length of day as a variable related to post-partum depression; one article linked the relationship of electric lighting and daylight photoperiod to breast cancer; three studies investigated light in relation to health-related quality of life, self-reported sleep latency, and depression; one article investigated the link between daylight exposure and burnout (a physiological term for the experience of long-term exhaustion and diminished interest); one article found that daylight hours influenced salivary cortisol levels; the final articles focused on health associations. Health associations noted included positive association with vision and sleep quality, and reduction of depression, myopia, eyestrain, ADHD (attention-deficit/hyperactivity disorder) prevalence, and SAD (seasonal affective disorder) depressions.
This literature review was limited to daylight and did not address issues related to gender, photoperiod sensitivity, and daily or monthly rhythms. Potential health interaction effects and interactions related to electric lighting also were not addressed.