Urban Lighting and Circadian Disruption: A Systematic Review and Policy Framework for Sustainable Nightscapes

Artificial light at night (ALAN) has surged greatly in the past decade, mainly due to the global shift to energy-efficient LED lighting. This sudden surge has triggered major concerns among scientists and public health experts about the potential impacts of ALAN on human circadian rhythms and sleep and health, highlighting the need for more research and possibly even lighting guidelines. This article will systematically review the researches on the impact of urban lighting on human circadian rhythm in the past in this article, we will screening and searching relevant studies using the PRISMA process system, and then we found that the short wavelength blue light induced inhibition of melatonin, delayed sleep, increased the risk of metabolic disorders; Simulation shows that "dynamic warm light curfew" can reduce the day and night loads by 35-50%. Based on the above, this article proposes that the current lighting standards cannot protect day and night health, and a "policy framework for time zone tailors' spectrum and timing to local solar and social time zones" should embed circadian metrics into municipal codes. The findings of this article provide evidence-based paths toward sustainable, healthy nightscapes.