Blood pressure changes in young male subjects exposed to a median altitude.

ABSTRACT

OBJECTIVE: Residence at high altitude has been associated with elevation in systemic blood pressure (BP), but few studies have been done on the time course and the effects of a median altitude. Moreover, there exist population differences in the reactions given to altitude and the mechanism is unknown. This study was therefore designed to determine the effects of a median altitude on resting BP and heart rate (HR) in a group of 15 healthy, young, Turkish male subjects. METHODS: After basic measurements were carried out in Bursa (155 m), subjects were transported to a mountain hotel (altitude 1,860 m), where the measurements were repeated once every 15 days during a 10-month period. RESULTS: Mean BP and diastolic BP increased on Day 4 and then remained above first values throughout the study. Compared with control measurements, high altitude increased systolic blood pressure (SBP) in all subjects, but in Month 4 and Month 6, SBP returned to control values, and remained elevated thereafter. HR continued to decrease in parallel with time and significant decrease occurred after Month 5. INTERPRETATION: Our findings imply that moderate-altitude living results in a significantly greater BP and lower HR over equivalent low-altitude measurements and we conclude that chronic exposure to hypobaric hypoxia at a median altitude causes increased parasympathetic and sympathetic tone in healthy, young, Turkish males.