Objective With the emergence of the “24-hour city” concept and the increasing diversification of the nighttime lifestyles and activities of urban residents, the impact of nighttime outdoor environments on public health has received growing attention. At the same time, the spatiotemporal heterogeneity of nighttime outdoor environments, in contrast to daytime conditions and activities, has intensified scholarly interest in the relationship between nighttime environmental factors and residents’ health. Although previous research has explored this relationship to some extent, a comprehensive and systematic understanding of the specific health effects and the underlying mechanisms remains limited. As research in this area continues to expand, there is an urgent need to synthesize existing knowledge, identify current limitations, and provide guidance for future investigations. In view of this, this research aims to develop an integrated perspective on the health impacts of nighttime outdoor environments, elucidate key mechanistic pathways, and evaluate measurement approaches for both environmental and health indicators. The ultimate goal is to provide a scientific foundation for health-oriented nighttime urban planning and policymaking.
Methods This research conducts a comprehensive review of Chinese and English literature on nighttime outdoor environments and public health, using publications retrieved from the Web of Science (WOS) and China National Knowledge Infrastructure (CNKI) databases that span the period from 1999 and 2025. A structured literature retrieval and screening process is applied to ensure relevance and quality. Research trends and key topics are analyzed and summarized across three main dimensions: Research focus, methodological approaches, and mechanistic pathways. The objective is to identify existing gaps and limitations in the literature and to inform future research directions.
Results 1) Current research primarily explores the health effects of nocturnal climatic factors (such as nighttime temperature, humidity, and air quality), auditory factors (such as nighttime environmental noise and natural sounds), and visual environmental factors (such as nighttime outdoor artificial lighting, streetscape, and urban architectural forms), with particular attention to their associations with cardiovascular health, sleep quality, psychological well-being, and cancer risk. However, the combined or synergistic effects of these environmental factors have been insufficiently investigated. For example, the way nighttime heat and humidity interact to jointly influence physiological stress and health risks is not well understood. Similarly, while night noise pollution is widely recognized as detrimental, the potential effects of natural sounds, such as rain sounds and wind sounds, on buffering or mitigating the perceived negative impact of noise pollution have received limited attention in existing research. 2) Key mechanistic pathways include circadian rhythm disruption, perceived nighttime safety, and engagement in nighttime recreational activities. Specifically, the nighttime outdoor environment acts as a critical factor in disrupting circadian rhythms by suppressing melatonin secretion, altering core body temperature regulation, and affecting nocturnal neural activity. Perceived safety serves as an important mediator of health outcomes, particularly for vulnerable populations such as women and the elderly, as it directly influences their willingness and motivation to participate in nighttime activities. Additionally, nighttime recreational activities function as a vital medium for interaction between individuals and their environment, with the realization of health benefits depending on the combined influence of multiple environmental factors. Together, these pathways synergistically shape the overall health impact of nighttime outdoor environments. However, existing research primarily relies on single exposure pathways, lacking a systematic investigation into how multisensory stimuli in nighttime environments influence physiological regulation, emotional responses, and behavioral changes through neural feedback mechanisms. Furthermore, such research often overlooks the potential dynamic interrelationships among these responses, particularly how physiological reactions, subjective perceptions, and behavioral outcomes interact with each other. 3) Existing research mainly utilizes remote sensing, field measurements, environmental monitoring, and subjective evaluations to collect environmental data. These are often combined with surveys, clinical diagnostics, or physiological assessments to evaluate health outcomes. However, limitations remain in terms of data precision, real-time monitoring, and dynamic analysis. In addition, existing research primarily focuses on the health impacts of static nighttime exposure levels, while overlooking the temporal dynamics of nighttime environmental factors and their quantitatively dynamic relationships with individuals’ actual exposure levels.
Conclusion Future research should apply a multidimensional approach that integrates environmental factors with advanced data collection and analytical methods to better understand the complex mechanisms linking nighttime outdoor environments to health outcomes. Specifically, future research should develop analytical models that account for interactions among natural, built, and social environmental components. It is also necessary to deepen the understanding of multilayered health impact pathways by establishing interdisciplinary frameworks that link environmental exposure, physiological stress, behavioral responses, and health outcomes. Moreover, efforts should focus on integrating multi-source data and encouraging methodological innovation to support the development of high-resolution, individualized exposure–response databases. The incorporation of emerging technologies, such as wearable sensors and ecological momentary assessment tools, offers promising opportunities to capture real-time, context-specific exposure data. These advancements will support more precise and dynamic analyses of exposure – health relationships and provide a robust scientific foundation for health-oriented nighttime urban planning and policymaking, ultimately contributing to improved public health and well-being during nighttime hours.
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