Adaptability of older adults to heat with reference to water balance

老年人对热应激的适应性与水分平衡的关系进行了评估。热适应对老年人水分平衡的影响研究将9名老年人和6名年轻人暴露在热运动应激下8天，比较第1天和第8天体温和水分平衡的调节反应。结果显示，老年受试者的体液量较低，水分和盐的损失较高，由于缺乏口渴而导致的水摄入量较低，水相关激素的反应性较低，对热的适应能力较差。我们认为这些因素与老年人中热伤亡率较高有关（提交给美国生理学杂志）。根据1968 ~ 1994年全国死亡统计资料，对中暑死亡的流行病学进行了分析。在日本，有热浪的年份报告的死亡人数约为150人，而1994年严重热浪的年份报告的死亡人数为589人。在中暑死亡中，64%为老年人（提交给International Journal of biomeorology）。脱水对体温调节的影响我们实验室对脱水对体温调节的影响的实验结果分为低血容量（脑研究进展，第115卷，脑功能热环境）和高渗透压（临床与基础药理学综述）的影响。本项目的实验结果表明，老年人中暑的高发生率与老年人体内较低的水分平衡水平有关。

Adaptability of older adults to heat stress was assessed in relation to water balance.1. Changes in water balance with heat acclimation in older adultsNine oIder and 6 younger adlts were exposed to heat-exercise stress for 8 days, and regulatory responses in body temperature and water balance were compared on the first and 8th day. The results obtained shown lower body fluid volumes, higher losses of water and salts, lower water intake due to the lack of thirst, lower responsiveness of water related hormones, and lesser acclimation to heat in older subject. It is suggested that these factors are relevant to the higher incidences of heat casualty in the elderly (submitted to American Journal of Physiology).2. Epidemiology of heat strokeBased on the National Death Statistics between 1968 and 1994, the epidemiology of heat stroke death was analyzed. About 150 deaths have been reported in the years with heat waves in Japan, while 589 cases were reported in 1994 with sever heat waves. Out of the heat stroke death, 64% were found in the elderly people (submitted to International Journal of Biometeorology).3. The effects of dehydration on body temperature regulationThe experimental results from our laboratory on the effects of dehydration on body temperature regulation were reviewed dividing the effect of hypovolemia (Progress in Brain Research, Vol. 115, Brain Function Hot Environment) and hyperosmolality (Reviews in Clinical & Basic Pharmacology).The experimental findings obtained in this projects suggests that the high incidences of heat casualty in the elderly are related to the lower level of water balance in older subjects.