Impact of plateau on antihypertensive efficacy among hypertensive highlanders : a post hoc analysis of the OMAN Trial

Background Epidemiological studies hint that the unique high-altitude environment may promote the prevalence of hypertension. Nevertheless, whether chronic plateau exposure would affect the antihypertensive efficacy in hypertensive highlanders remains unclear. Purpose To investigate whether chronic plateau exposure would affect the antihypertensive efficacy in hypertensive highlanders. Methods Hypertension patients in the OMAN Trial were divided into highlanders (Tibetan Plateau, altitude≈3000m) and lowlanders (altitude≈500m) according to 1:1 propensity score. After taking the same dose of olmesartan/amlodipine for 4 weeks, office and ambulatory blood pressure (BP) reduction, BP control rate as well as BP rhythm were compared between the two groups to evaluate the influence of plateau on the efficacy of antihypertensive drugs. Results The plateau and plain group each comprised 171 hypertensive patients with comparable baselines. The reduction in office BP and 24-hour BP in highlanders was less than that in lowlanders (difference in 24 SBP reduction: -2.39 mmHg, P=0.048; difference in 24h DBP reduction: -1.60 mmHg, P=0.025). More specifically, highlanders exhibited inferior reductions in morning BP and daytime BP relative to lowlanders. Similarly, both the office BP control rate (77.2% in highlanders vs. 60.2% in lowlanders, P = 0.001) and the 24-hour BP control rate (50.9% in highlanders vs. 34.5% in lowlanders, P = 0.002) were lower in highlanders. Intriguingly, though, there were no statistically significant differences in either nocturnal BP reduction or nocturnal BP control rates between the two groups. Conclusions Our study suggests that chronic plateau exposure may attenuate the efficacy of antihypertensive drugs in the Tibetan highlanders.