Greenspace exposure and sleep: A systematic review.

Green space is considered a critical environmental factor for sleep quality and quantity. However, no systematic review exploring this relationship exists. The purpose of this systematic review was to 1) explore research related to green space and sleep, and 2) examine the impact of green space exposure on sleep quality and quantity. Papers from eight electronic databases were eligible for inclusion if they met the following criteria: well-designed, any analysis exploring green space and sleep, provided sleep and green space measurement, published in peer-reviewed journals, and written in English. Thirteen eligible studies related to green space and sleep were selected after peer-review procedures. Cross-sectional studies (n = 7) used either a questionnaire or the combination of Geographic Information Systems and remote sensing images for green space measurement, while questionnaires were primarily used to measure both sleep quality and quantity. Intervention studies (n = 5) were categorized into three types: walking program, gardening, and working in a forest. Eleven out of thirteen studies concluded that green space exposure was associated with improvement in both sleep quality and quantity. The findings support the evidence of a positive association between green space exposures and sleep quality and quantity, and also suggest green exercise and therapeutic gardening as possible intervention methods to improve sleep outcomes.