To clarify possible involvement of hot spring bathing in the occurrence of acute myocardial infarction and cerebral infarction at Kusatsu, its effects on blood pressure, heart rate, plasma cortisol and hematocrit were examined in 9 healthy young men. Abrupt increase in systolic blood pressure was observed immediately after starting a 3-minute 47°C or a 10-minute 42°C hot-spring bath. Both systolic and diastolic blood pressure were abruptly decreased one minute after completing either 47°C or 42°C bathing. The heart rate was increased gradually after the start of either 47°C or 42°C bathing and was decreased gradually after the completion of either 47°C or 42°C bathing. It was considered that the plasma Cortisol level was increased 15 minutes after starting 47°C bathing and the hematocrit was increased 15 minutes after starting 42°C bathing. We have already reported that fibrinolytic activity was decreased and platelet function was activated by 47°C bathing. Taken together, it is suggested that the mechanism of the occurrence of thrombotic diseases after hot spring bathing may be explained by considering transient changes in blood pressure, heart rate, blood viscosity, fibrinolytic activity and platelet function induced by hyperthermal stress.
