Blood pressure and hypertension in people living at high altitude in Nepal

This study aimed to describe blood pressure (BP) and hypertension (HT) in samples of high altitude populations of Nepal and to explore associations of systolic and diastolic BP with altitude. This was a cross-sectional survey of cardiovascular disease and associated risk factors among 521 people living at four different altitude levels, all above 2800 m, in the Mustang and Humla districts of Nepal. Data on BP was available for all 521 participants. Systolic and diastolic BP levels were highest at the altitude of 3620 m (the highest area surveyed) but did not consistently increase with altitude. Using the cut-point of ≥ 140/90 mmHg (systolic/diastolic), the prevalence of HT (or on anti-hypertensive medication) was 46.1%, 40.9% and 54.5%, respectively, at 2800, 3270 and 3620 m of Mustang district, and 29.1% at 2890 m of Humla district. In a multivariate model adjusting for potential confounders, there was strong evidence of a relationship between systolic BP and altitude; mean systolic BP increased by 15.6 mmHg (95% CI: 4.0-27.2), P = 0.009 for every 1000 m elevation. Although diastolic BP and the probability for HT or on anti-hypertensive medication also tended to increase with increasing altitude levels, there was no evidence of a relationship. In the present study three out of four communities living at higher altitude levels showed a greater prevalence of HT among those aged 30 years or older compared with the overall national data. These findings indicate a probable high risk of raised BP in high altitude populations in Nepal.