Review on health effects of indoor and outdoor artificial light at night

A growing number of urban dwellers are being exposed to excessively bright artificial night light induced by the development of high-intensity, high-density cities around the world. The adverse health effects of artificial light at night (ALAN) are increasingly becoming a global public health issue. Investigating the effects of built environment, especially ALAN, on public health has progressively developed into a cross-disciplinary research hotspot since the World Health Organization launched the Healthy Cities Project. Numerous studies found the links between ALAN and multiple negative health outcomes. However, to date, no review has summarized the health impacts of ALAN in China. This article systematically outlined the progress of research on the health effects of indoor and outdoor ALAN, including sleep disorders, obesity, cancers, cardiovascular diseases, metabolic diseases, cognitive function, and mental health. We pointed out the limitations of current research such as errors in exposure assessment, lack of research in developing countries, weak causal argument, and difficulty in controlling confounding factors. Future research should improve study design, conduct quantitative studies, and explore potential mechanisms, so as to provide scientific evidence for improving urban lighting planning and urban architectural design.