Effects of low altitude exposure on 24-hour blood pressure and adrenergic activity

The circulatory response to acute exposure to high altitude (>3,000 m) has been extensively studied. 1–3 Sympathetic activation that occurs immediately after the exposure produces an abrupt increase in blood pressure (BP) and heart rate (HR), which persists for a few days. 4,5 Subsequently, both BP and HR gradually return to normal levels. In contrast, the circulatory changes caused by exposure to a lower altitude (< 1,800 m) have not been well studied even though increasing numbers of people are spending holidays in the mountains. How should a clinician advise the hypertensive patient who asks if he is allowed to spend a holiday in the mountains? The present study evaluates the effect of a short stay in the mountains (1,200 m) on 24-hour ambulatory BP levels and on adrenergic activity.