Effects of acute exposure to moderate altitude on vascular function, metabolism and systemic inflammation

Abstract

Background: Travel to mountain areas is popular. However, the effects of acute exposure to moderate altitude on the cardiovascular system and metabolism are largely unknown.

Objectives: To investigate the effects of acute exposure to moderate altitude on vascular function, metabolism and systemic inflammation.

Methods: In 51 healthy male subjects with a mean (SD) age of 26.9 (9.3) years, oxygen saturation, blood pressure, heart rate, arterial stiffness, lipid profiles, low density lipoprotein (LDL) particle size, insulin resistance (HOMA-index), highly-sensitive C-reactive protein and pro-inflammatory cytokines were measured at 490 m (Zurich) and during two days at 2590 m, (Davos Jakobshorn, Switzerland) in randomized order. The largest differences in outcomes between the two altitudes are reported.

Results: Mean (SD) oxygen saturation was significantly lower at 2590 m, 91.0 (2.0)%, compared to 490 m, 96.0 (1.0)%, p<0.001. Mean blood pressure (mean difference +4.8 mmHg, p<0.001) and heart rate (mean difference +3.3 bpm, p<0.001) were significantly higher at 2590 m, compared to 490 m, but this was not associated with increased arterial stiffness. At 2590 m, lipid profiles improved (median difference triglycerides -0.14 mmol/l, p=0.012, HDL +0.08 mmol/l, p<0.001, total cholesterol/HDL-ratio -0.25, p=0.001), LDL particle size increased (median difference +0.45 nm, p=0.048) and hsCRP decreased (median difference -0.18 mg/l, p=0.024) compared to 490 m. No significant change in pro-inflammatory cytokines or insulin resistance was observed upon ascent to 2590 m.

Conclusions: Short-term stay at moderate altitude is associated with increased blood pressure and heart rate likely due to augmented sympathetic activity. Exposure to moderate altitude improves the lipid profile and systemic inflammation, but seems to have no significant effect on glucose metabolism.

Trial registration: ClinicalTrials.gov NCT01130948.

Figure 1. Study flow.

Figure 2. Effects of moderate altitude on lipids.

Black lines represent medians. Panel A shows individual high density lipoprotein (HDL) blood levels in Zurich (490 m) and Davos Jakobshorn (2590 m). HDL was higher on both days (d1, d2) at 2590 m compared to 490 m. *p<0.001 vs 490 m. Panel B shows individual total cholesterol/high density lipoprotein (HDL) ratios in Zurich (490 m) and Davos Jakobshorn (2590 m). Total cholesterol/HDL ratio was lower on both days (d1, d2) at 2590 m compared to 490 m. *p<0.05 vs 490 m. Panel C shows individual triglyceride blood levels in Zurich (490 m) and Davos Jakobshorn (2590 m). Triglycerides were lower on day 2 at 2590 m compared to 490 m. *p<0.05 vs 490 m.

Figure 3. Effects of moderate altitude on LDL diameter.

Scatterplot showing individual median low density lipoprotein (LDL) diameter in Zurich (490 m) and Davos Jakobshorn (2590 m) during day 1 and day 2. Black lines represent medians. LDL diameter was larger on both days at 2590 m compared to 490 m. *p<0.05 vs 490 m.

Figure 4. Effects of moderate altitude on C-reactive protein.

Scatterplot showing individual highly sensitive C-reactive protein (hsCRP) blood levels in Zurich (490 m) and Davos Jakobshorn (2590 m). Black lines represent medians. HsCRP levels were lower on day 1 at 2590 m compared to 490 m. *p<0.05 vs 490 m.