Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada.
Harvard T.H. Chan School of Public Health, Harvard University, Boston, Massachusetts, USA.
Environ Health Perspect. 2024 Feb;132(2):27003. doi: 10.1289/EHP13159. Epub 2024 Feb 8.
Health agencies recommend that homes of heat-vulnerable occupants (e.g., older adults) be maintained below 24-28°C to prevent heat-related mortality and morbidity. However, there is limited experimental evidence to support these recommendations.
To aid in the development of evidence-based guidance on safe indoor temperatures for temperate continental climates, we evaluated surrogate physiological outcomes linked with heat-related mortality and morbidity in older adults during simulated indoor overheating.
Sixteen older adults [six women; median age: 72 y, interquartile range (IQR): 70-73 y; body mass index: ] from the Ottawa, Ontario, Canada, region (warm summer continental climate) completed four randomized, 8-h exposures to conditions experienced indoors during hot weather in continental climates (e.g., Ontario, Canada; 64 participant exposures). Ambient conditions simulated an air-conditioned environment (22°C; control), proposed indoor temperature upper limits (26°C), and temperatures experienced in homes without air-conditioning (31°C and 36°C). Core temperature (rectal) was monitored as the primary outcome; based on previous recommendations, between-condition differences were considered clinically meaningful.
Compared with 22°C, core temperature was elevated to a meaningful extent in 31°C [; 95% confidence interval (CI): 0.5, 0.8] and 36°C (; 95% CI: 0.8, 1.1), but not 26°C (, 95% CI: 0.0, 0.3). Increasing ambient temperatures were also associated with elevated heart rate and reduced arterial blood pressure and heart rate variability at rest, as well as progressive impairments in cardiac and blood pressure responses to standing from supine.
Core temperature and cardiovascular strain were not appreciably altered following 8-h exposure to 26°C but increased progressively in conditions above this threshold. These data support proposals for the establishment of a 26°C indoor temperature upper limit for protecting vulnerable occupants residing in temperate continental climates from indoor overheating. https://doi.org/10.1289/EHP13159.
卫生机构建议，易感热人群（如老年人）的居所温度应保持在 24-28°C 以下，以预防与热相关的死亡和发病。然而，支持这些建议的实验证据有限。
为了帮助制定基于证据的温带大陆性气候下室内安全温度指南，我们评估了与老年人在模拟室内过热期间与热相关的死亡和发病相关的替代生理结果。
来自加拿大安大略省渥太华地区（温暖的大陆性夏季气候）的 16 名老年人（6 名女性；中位年龄：72 岁，四分位距（IQR）：70-73 岁；体重指数：）完成了四项随机、8 小时的暴露于大陆性气候炎热天气期间室内经历的条件（例如，加拿大安大略省；64 名参与者暴露）。环境条件模拟空调环境（22°C；对照）、拟议的室内温度上限（26°C）和无空调家庭的温度（31°C 和 36°C）。核心温度（直肠）被监测为主要结果；根据先前的建议，认为条件之间的差异具有临床意义。
与 22°C 相比，31°C 时核心温度升高到有意义的程度 [; 95%置信区间（CI）：0.5，0.8]和 36°C （; 95% CI：0.8，1.1），但 26°C 时没有升高（，95% CI：0.0，0.3）。环境温度升高还与静息时心率升高和动脉血压及心率变异性降低有关，以及从仰卧位站立时的心脏和血压反应逐渐受损。
8 小时暴露于 26°C 后，核心温度和心血管压力没有明显改变，但在超过此阈值的条件下逐渐增加。这些数据支持为保护居住在温带大陆性气候中的脆弱人群免受室内过热而建立 26°C 室内温度上限的建议。
