Table_3_Human Physiology During Exposure to the Cave Environment: A Systematic Review With Implications for Aerospace Medicine.DOCX

Background: Successful long-duration missions outside low-Earth orbit will depend on technical and physiological challenges under abnormal environmental conditions. Caves, characterized by absence of light, confinement, three-dimensional human movement and long-duration isolation, are identifiably one of the earliest examples of scientific enquiry into space analogs. However, little is known about the holistic human physiological response during cave exploration or prolonged habitation.
Objectives: The aim of our review was to conduct a systematic bibliographic research review of the effects of short and prolonged exposure to a cave environment on human physiology, with a view to extend the results to implications for human planetary exploration missions.
Methods: A systematic search was conducted following the structured PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines for electronic databases.
Results: The search retrieved 1,519 studies. There were 50 articles selected for further consideration, of which 31 met our inclusion criteria. Short-term cave exposure studies have investigated visual dysfunction, cardiovascular, endocrine-metabolic, immunologic-hematological and muscular responses in humans. Augmentations of heart rate, muscular damage, initial anticipatory stress reaction and inflammatory responses were reported during caving activity. Prolonged exposure studies mainly investigated whether biological rhythms persist or desist in the absence of standard environmental conditions. Changes were evident in estimated vs. actual rest-activity cycle periods and external desynchronization, body temperature, performance reaction time and heart rate cycles. All studies have shown a marked methodological heterogeneity and lack reproduction under controlled conditions.
Conclusions: This review facilitates a further comparison of the proposed physiological impact of a subterranean space analog environment, with existing knowledge in related disciplines pertaining to human operative preparation under challenging environmental conditions. This comprehensive overview should stimulate more reproducible research on this topic and offer the opportunity to advance study design and focus future human research in the cave environment on noteworthy, reproducible projects.

研究背景：近地轨道之外的长期载人深空任务，其成败将取决于异常环境条件下的技术与生理挑战。洞穴以无光环境、空间局促、需三维人体运动以及长期隔离为特征，被公认为太空模拟环境（space analogs）领域最早的科学探索案例之一。然而，目前学界对洞穴探索或长期驻留期间人体的整体生理反应仍知之甚少。
研究目标：本综述旨在对短期及长期暴露于洞穴环境对人体生理的影响开展系统性文献综述，以期将研究结果推广至载人行星探测任务的相关应用场景。
研究方法：本研究遵循结构化PRISMA（系统评价与元分析首选报告条目，Preferred Reporting Items for Systematic Reviews and Meta-Analyses）指南，对电子数据库进行系统性检索。
研究结果：本次检索共获取1519篇文献，其中50篇进入进一步筛选环节，最终31篇符合纳入标准。短期洞穴暴露相关研究已探讨了人体的视觉功能障碍、心血管、内分泌代谢、免疫血液及肌肉系统的生理反应。研究显示，洞穴活动期间会出现心率升高、肌肉损伤、初始预期性应激反应及炎症反应增强等情况。长期洞穴暴露研究主要探讨了在缺乏标准环境条件下，生物节律是否会持续或消失。研究发现，预估与实际静息-活动周期时长、外部去同步化、体温、反应时表现及心率周期均出现变化。所有研究均存在显著的方法学异质性，且无法在受控条件下实现重复验证。
研究结论：本综述有助于将地下太空模拟环境（subterranean space analog environment）所产生的潜在生理影响，与现有相关学科中关于挑战性环境下人体作业准备的认知进行进一步对比。本次全面综述旨在推动该主题下更具可重复性的研究，并为优化研究设计提供思路，同时可聚焦于开展有价值、可重复的洞穴环境人体研究项目。