Adaptability of older adults to heat with reference to water balance

根据水平衡来评估老年人对热应激的适应性。9名老年人和6名青年受热运动应激8天，并在第1天和第8天比较体温和水分平衡的调节反应。结果显示，老年受试者的体液容量较低，水分和盐分的损失较多，由于缺乏口渴而摄入的水较少，与水有关的激素的反应性较低，对热的适应性较差。这表明这些因素与老年人较高的中暑死亡率有关(提交给《美国生理学杂志》)。中暑流行病学根据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。据报道，近几年来，日本约有150人死于热浪，而1994年有589例死于严重的热浪。在中暑死亡中，%是在老年人中发现的(提交《国际生物气象杂志》)。脱水对体温调节的影响本实验室从低血容量(《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》)两个方面对本实验室有关脱水对体温调节影响的实验结果进行了综述。实验结果表明，老年人中暑的发生率较高，与老年人水平衡水平较低有关。

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.