There are conflicting indications on a potential association between altitude and blood pressure. Many population studies are conducted at an altitude with a relatively narrow range of variability. This study uses a unique opportunity from a population-based survey to study the blood pressure of residents living at altitudes from 450 to 1200 meters in Nepal. Thus, the objective of this study was to explore the relationship between altitude and blood pressure.Design and Method:
The data analysis was carried out using the baseline survey data of the project: “Community based management of hypertension in Nepal”. Out of 2815 observations 2557 were included in this study. Those on anti-hypertensive medication (n = 257) and one who had missing altitude data (n = 1) were excluded. The exposure variable altitude was log transformed to approximate normal distribution. Wilcoxon rank-sum test was used to explore the differences between categories of variables in altitude. Multiple linear regression analysis was conducted to explore association between blood pressure and altitude. Adjustment was made for cardiovascular risk confounders (age, sex, obesity, physical activity, education, ethnicity, tobacco use, and alcohol use).Results:
Mean systolic and diastolic blood pressures were 124.28 ± 18.57 mmHg and 81.20 ± 11.23 mmHg, respectively. Multiple linear regression analysis revealed that if altitude is increased by 20% we expect systolic and diastolic blood pressure to decrease by 1.46 (95% CI: −2.36; −0.57) mmHg and 0.99(95% CI: −1.56; −0.42) mmHg, respectively.Conclusions:
There is a significant inverse association between blood pressure and altitude. Interestingly this association remains after adjustment for known cardiovascular risk factors. This suggests that living in higher altitudes may have a positive physiological effect on blood pressure.