Physiological and perceptual responses in the elderly to simulated daily living activities in UK summer climatic conditions

Objectives: The elderly population is at an increasingly significant health risk to heat-related illnesses and mortality when compared with younger people in the same conditions. This is due to an increased frequency and severity of heatwaves, attributed to climate change, and reduced ability of elderly individuals to dissipate excess heat. Consequently, most excess deaths and emergency visits during heatwaves occur in people aged more than 65 years. The aim of this investigation was to assess the physiological and perceptual responses of elderly people during exercise sessions equating to activities of daily living in UK summer climatic conditions. Study design: Mixed-method, randomised research design. Methods: Twenty-eight participants (17 males, 10 females and 1 transgender female) were randomly assigned into three experimental groups; 15°C, 25°C or 35°C, with 50% relative humidity. Participants completed one preliminary and three experimental trials within their assigned environment. The data from the preliminary incremental recumbent cycling test was used to calculate participant's individual exercise intensities equating to 2, 4 and 6 metabolic equivalents (METs) for the subsequent trials. During experimental trials, participants completed 30-min seated rest and 30-min cycling. Results: No change was observed in thermal comfort ([TC] just uncomfortable in both trials), and only modest changes in ratings of perceived exertion (14 ± 2 vs 15 ± 2) at 6 METs in 25°C compared with those in 35°C were observed. In contrast, thermal strain markers did significantly increase (P < 0.05) across the same conditions, including change in rectal temperature (ΔTre) during exercise (0.27 ± 0.17°C vs 0.64 ± 0.18°C) and peak skin temperature ([Tskin] 32.94 ± 1.15°C vs 36.11 ± 0.44°C). Conclusion: When completing exercise that equates to activities of daily living, elderly people could have a decreased perceptual awareness of the environment even though physiological markers of thermal strain are elevated. Consequently, the elderly could be less likely to implement behavioural thermoregulation interventions (i.e. seek shade and/or remove excess layers) due to a decreased awareness of an increasingly thermally challenging environment.

研究目的：与相同环境下的年轻人相比，老年人群罹患热相关疾病及发生热相关死亡的健康风险日益攀升。这一现象的成因包括气候变化导致热浪的发生频率与严重程度均有所增加，以及老年个体散发热量的能力下降。因此，热浪期间绝大多数超额死亡与急诊就诊病例均发生于65岁以上人群。本研究旨在评估英国夏季气候条件下，老年人进行等同于日常活动的运动时的生理与感知反应。
研究设计：混合方法随机研究设计。
研究方法：招募28名受试者（17名男性、10名女性、1名跨性别女性），将其随机分配至15℃、25℃或35℃的实验环境中，环境相对湿度均为50%。所有受试者均在各自分配的环境中完成1次预备试验与3次正式试验。利用预备性递增负荷卧式骑行试验的数据，计算得到受试者后续试验中对应2、4、6代谢当量（metabolic equivalents, METs）的个体化运动强度。正式试验期间，受试者先完成30分钟静坐休息，随后进行30分钟骑行运动。
研究结果：与25℃环境下相比，35℃环境下6代谢当量运动时的热舒适度（thermal comfort）无明显变化，热舒适度评分显示两次试验均仅为轻度不适；自觉劳累分级评分（ratings of perceived exertion）仅出现小幅变化（14 ± 2 vs 15 ± 2）。与之相反，相同条件下的热应激标志物（thermal strain markers）则出现显著升高（P < 0.05），包括运动期间的直肠温度变化量（ΔTre）（0.27 ± 0.17℃ vs 0.64 ± 0.18℃）与峰值皮肤温度（peak skin temperature）（32.94 ± 1.15℃ vs 36.11 ± 0.44℃）。
研究结论：当老年人进行等同于日常活动的运动时，即便热应激的生理标志物水平升高，其对环境的感知觉知能力可能有所下降。因此，由于对日益严峻的热应激环境觉知不足，老年人采取行为性体温调节干预措施（behavioural thermoregulation interventions）的可能性可能更低。