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

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.