Blood Pressure Responses in Young Adults First Exposed to High Altitude for 12 Months at 3550 m

Abstract

To determine the changes in blood pressure (BP) and related variables in sea-level young adults with chronic exposure to high altitude, a longitudinal study was performed in male army recruits (n = 346; age 17.9 +/- 0.1 yr; BMI, 22.5 +/- 0.3 kg/m(2)) first exposed to 3550-m altitude for 12 months. Fifty male recruits (age 17.8 +/- 0.6 and BMI 22.6 +/- 0.3 kg/m(2)) never exposed to altitude were used as controls. A sustained higher mean diastolic BP (DBP) (82.1 +/- 1.0 mmHg at month 3; 81.3 +/- 0.9 mmHg at month 12) was observed, compared to first exposure and the control group (p < 0.001). The BP values were always higher than those of the sea-level control group (systolic blood pressure (SBP) 109 +/- 2.3 and DBP 67.4 +/- 0.8; p < 0.001), and a large proportion of subjects steadily presented overoptimal values for either systolic BP (SBP) (64%) or DBP (77%) and hypertensive DBP values (40%). The higher DBP was associated with lower Sao(2) (OR = 0.919; p < 0.05). In addition, the acute mountain sickness (AMS) score showed a slight decrease during re-exposure (3.9 +/- 0.3 vs.3.4 +/- 0.3; p < 0.001) and an inverse association to the before-descending Sao(2) at month 3 (OR = 0.906, p < 0.01). These data suggest that BP stabilization can take longer than currently thought and that each parameter has a different profile of change. Further, a sustained high DBP should be a matter of epidemiological concern and emphasizes the need for BP monitoring among young lowlanders exposed to high altitude.

Hypoxic training: Clinical benefits on cardiometabolic risk factors

“…However, in one study [21], both SBP and DBP reduced after hypoxic training, 26mmHg and 8mmHg respectively, while increases in SBP and DBP were reported another study [22]. Chronic exposure to hypoxic training for ≥ three weeks resulted in mixed findings, with one study reporting reductions in SBP and DBP (p<0.05) [6] two studies [23,24] reporting increase in both SBP and DBP, and no change in one study [9]. Higher levels of altitude ≥ 4000m increased both SBP and DBP [22][23][24], while at moderate levels of altitude (1,700m-2,740m), blood pressure levels either maintained or improved [6,7,9,19,21].…”

“…Higher levels of altitude ≥ 4000m increased both SBP and DBP [22][23][24], while at moderate levels of altitude (1,700m-2,740m), blood pressure levels either maintained or improved [6,7,9,19,21]. Although improvements in SBP and DBP were not evident in healthy subjects [9,[18][19][20][22][23][24][25], patients diagnosed with hypertension resulted in 8-13mmHg [6,7,21] reduction in DBP and up to 26mmHg [21] reduction in SBP at altitudes of 1,285m-2,650m [6,7,21]. With patients with obesity (BMI ≥30kg/m 2 ), one week of exposure to altitude of 2650m resulted in DBP reduction of 13.9% [7], however ,no change in blood pressure were observed with non-hypertensive patients with obesity [9].…”

“…Besides hypoxia, such factors may contribute to changes in blood pressure especially with studies that used mountainous exposure as a form of hypoxic training [6,7,21,22,24].…”

“…Moreover, only two [6,24] of those studies had a control group at a normoxic environment. The increase in both SBP and DBP at higher altitudes may be attributed by the higher hypoxic stress imposed on the body, causing heightened sympathetic responses including increased secretion of hormones like epinephrine and noradrenaline [14,35].…”

Acute mountain sickness

“…found AMS in almost 60% of the population. Three months later when soldiers descended to the lowland for over a week and re-ascended, the symptoms of AMS were noted in 55% [27]. Still another study in tourists climbing Kilimanjaro the symptoms of acute mountain sickness were observed in 9% of participants at the altitude of 2743 m a.s.l.…”