Objective Sleep disorders pose a significant threat to the physical and mental health of older adults and have emerged as one of the key public health challenges in aging societies. As a core component of healthy aging, sleep health not only directly influences neurocognitive function and metabolic homeostasis but also exacerbates the burden of chronic diseases and social care pressures through comorbid mechanisms, and thus serves as a critical focal point for addressing health challenges in aging populations. As accessible natural elements within urban environments, green spaces offer unique advantages for improving environmental quality, regulating microclimates, and promoting physical and mental relaxation, offering new perspectives for interventions targeting sleep health among older adults. For example, natural environments may enhance sleep health through regulating older adults' circadian rhythms (e.g., increasing daytime light exposure) or by improving mental health (e.g., reducing depression risk). However, current research remains fragmented regarding the underlying mechanisms and lacks systematic integration of optimization pathways. This gap urgently necessitates in-depth exploration from multidisciplinary perspectives. This study aims to synthesize multidisciplinary theories in order to construct a systematic evidence framework elucidating the association between urban green spaces and sleep health in older adults, thereby providing a scientific basis for optimizing the design of age-friendly urban spaces.
Methods The authors searched the Web of Science database for English-language studies published since 2000 investigating the role of green spaces in promoting sleep health in older adults. The Chinese database CNKI was used to search for Chinese-language literature. The inclusion criteria were as follows: 1) Study participants aged ≥60 years; 2) research types included empirical studies, reviews, and meta-analyses; 3) publications in Chinese or English, with publication dates ranging from January 1, 2000, to the search cutoff date. The exclusion criteria included: 1) Non-academic literature; 2) studies with content unrelated to sleep health in older adults; 3) studies with inaccessible full texts or incomplete data; 4) duplicate publications. Initially, two researchers independently screened the literature based on the criteria. Subsequently, they conducted a re-screening. Any disagreements were resolved through discussion or, if necessary, by a third researcher. A total of 452 studies were ultimately identified for inclusion and analysis.
Results Our analysis revealed that relevant research primarily focuses on disciplines including geriatrics and gerontology, neuroscience and neurology, psychiatry, psychology, behavioral science, sociology, rehabilitation medicine, exercise science, environmental science, and ecology. The decline in sleep quality among older adults stems from the interplay between age-related physiological decline and multiple environmental factors. The underlying mechanisms can be categorized into two dimensions: 1) Intrinsic physiological-psychological mechanisms: This includes degenerative changes in sleep structure and circadian rhythms, along with the superimposed effects of chronic diseases; 2) extrinsic environmental stress systems: This encompasses stress responses induced by noise pollution, circadian rhythm disruption resulting from light pollution, oxidative stress damage caused by carbon-oxygen imbalance and air pollution, as well as the environmental-psychological dilemmas associated with social isolation. Urban green spaces contribute to regulating circadian rhythms, prolonging deep sleep duration, and reducing sleep fragmentation via multiple pathways. 1) Environmental regulation: Improving microclimates through green vegetation, optimizing air quality, and attenuating noise to enhance the acoustic environment; 2) behavioral promotion: Facilitating physical activity within green spaces; 3) social support: Cognitive restoration promoted by natural landscapes and the environmental-psychological benefits of social interaction; 4) stress relief: natural regulation of HPA axis activity and green-mediated inhibition of inflammatory responses; 5) circadian regulation: Regulation via natural light exposure. Significant individual variations in these health benefits, influenced by genetics, were also identified. Genetically, polymorphisms in circadian rhythm genes influence sleep patterns in older adults. Consequently, individuals with different genetic backgrounds exhibit varying responses to sleep improvement from green space exposure, attributable to differences in baseline circadian rhythms and sleep homeostasis regulation. Regarding the microbiome, the gut-brain axis plays a crucial role. Older adults with genetically susceptible gut microbiota may experience distinct sleep improvement effects from green spaces compared to those with more stable gut microbiota compositions. Additionally, culturally-specific lifestyle patterns and attitudes towards nature may lead to variations in sleep improvement outcomes among older adults from diverse cultural backgrounds when utilizing green spaces.
Conclusion Research on improving sleep health in older adults must transcend single-discipline limitations, integrating theories and research methods from multiple fields including geriatrics and gerontology, neuroscience and neurology, psychiatry, psychology, behavioral science, sociology, rehabilitation medicine, exercise science, and environmental science and ecology. This interdisciplinary approach is essential to collaboratively unravel the pathways of the “green spaces-physiological+psychological responses-leep quality” mechanism. To further improve sleep quality in older adults, it is essential to enhance the ‘intervention dosage’ (impact) of urban green spaces through multi-dimensional approaches and establish a systematic, precision-oriented ‘green sleep prescription’ system. As the primary and most frequently accessed green spaces for older adults, community green spaces and residential greening constitute critical foundational elements for enhancing sleep health. Leveraging their inherent advantages of convenient accessibility and high usage frequency, they play an irreplaceable, proactive, and sustained role in improving sleep quality. Consequently, prioritizing the advancement of their planning, design, and functional optimization is imperative. Finally, rigorous evaluation of the effectiveness of sleep quality improvement interventions is essential. In summary, future research should establish a complete closed loop of "scientific research- prescription development-design implementation- effect evaluation," grounded in deepened mechanistic understanding. This effort should focus on achieving breakthroughs in precision design and tailored activity plans for diverse older adult groups, providing innovative solutions for healthy aging and a scientific basis for implementing the Healthy China Strategy.
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