Background
Hypertension is the most common cardiovascular disease among those recreating at high altitude. Previous studies with smaller, more homogenous participant pools have demonstrated increases, decreases, and no change in blood pressure (BP). We sought to characterize how BP changes with altitude on both a population-wide and individual level in normotensive (NTN) and hypertensive (HTN) trekkers in Nepal.
Methods
Trekkers in the Solukhumbu Valley of Nepal, aged 18 years and older, were recruited at 2860 m. They reported demographic information, medical history, and medications. Resting BP was recorded at 2860 m, 3400 m, and 4300 m on ascent and descent. Responses were compared between NTN and HTN subjects and across altitudes.
Results
We enrolled 604 NTN and 60 self-reported HTN trekkers. At 2860 m, mean systolic BPs (SBP) in NTN and HTN trekkers were elevated relative to self-reported home measurements (n = 303, mean difference = 9 mm Hg [95% CI 5-13], P < .05). Mean SBP did not differ between altitudes on ascent or descent (P > .05) but was higher in HTN vs NTN subjects at each altitude (P < .05). However, we observed large interindividual variability. Between 2860 m and 3400 m, the majority (60%, n = 284) of NTN SBPs did not change, while 21% (n = 102) increased >10 mm Hg and 19% (n = 91) decreased >10 mm Hg. The pattern was similar in NTNs between 3400 m and 4300 m: (65% [n = 202] no change, 21% [n = 65] increased, 15% [n = 46] decreased). A greater proportion of HTN trekkers had SBP decreases between 2860 m and 3400 m (45% [n = 19] no change, 19% [n = 8] increased, 36% [n = 15] decreased) and between 3400 m and 4300 m (44% [n = 10], 26% [n = 6], 30% [n = 7]), respectively.
Conclusions
In most individuals, with and without HTN, BP is likely to change less than 10 mm Hg at altitudes up to 4300 m. In general, travelers, including those with well-controlled HTN, may be reassured that their blood pressure will remain relatively stable at high altitude.
Funding
WMS Hultgren Grant (2014).