Altitude and hypertension
‘Tibet is known as the ‘Third Pole’ and is one of the highest inhabited areas of the world.’
There is a controversy about the impact of altitude on blood pressure. So, will living at high altitude predispose you to high blood pressure?
To address this question, we searched four different scientific databases to identify human studies investigating the relationship between high altitude and the prevalence of hypertension in Tibet – one of the highest altitude regions of the earth with average altitude of 4500 m above sea levels. We then used statistical techniques to explore the relationships between altitude and prevalence, and to also calculate the degree of changes in the prevalence of hypertension with changing altitudes.
In total, we identified eight survey studies with a total of 16,913 Tibetan participants. The altitude in the studies was between 3000 and 4300 m, which is below the average altitude in Tibet. The prevalence of hypertension was between 23% and 56%, and there was no evidence that gender was a factor.
We observed a significant relationship between altitude and the prevalence of hypertension; indeed for every 100 m increase in altitude, there was a corresponding 2% increase in the prevalence of hypertension. In addition, we found that the socioeconomic status of participants had an influence on the rates of awareness and subsequent control and treatment of hypertension.
So when next you encounter anyone who dwells at high altitude, or has travelled to a high-altitude region, ask them if they’ve recently had their blood pressure checked.
Relationship between altitude and the prevalence of hypertension in Tibet: a systematic review.
Mingji C, Onakpoya IJ, Perera R, Ward AM, Heneghan CJ.
Heart. 2015 May 7. pii: heartjnl-2014-307158. doi: 10.1136/heartjnl-2014-307158
Introduction Hypertension is a leading cause of cardiovascular disease, which is the cause of one-third of global deaths and is a primary and rising contributor to the global disease burden. The objective of this systematic review was to determine the prevalence and awareness of hypertension among the inhabitants of Tibet and its association with altitude, using the data from published observational studies.
Methods We conducted electronic searches in Medline, Embase, ISI Web of Science and Global Health. No gender or language restrictions were imposed. We assessed the methodological characteristics of included studies using the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) criteria. Two reviewers independently determined the eligibility of studies, assessed the methodology of included studies and extracted the data. We used meta-regression to estimate the degree of change in hypertension prevalence with increasing altitude.
Results We identified 22 eligible articles of which eight cross-sectional studies with a total of 16 913 participants were included. The prevalence of hypertension ranged between 23% and 56%. A scatter plot of altitude against overall prevalence revealed a statistically significant correlation (r=0.68; p=0.04). Meta-regression analysis revealed a 2% increase in the prevalence of hypertension with every 100 m increase in altitude (p=0.06). The locations and socioeconomic status of subjects affected the awareness and subsequent treatment and control of hypertension.
Conclusions The results from cross-sectional studies suggest that there is a significant correlation between altitude and the prevalence of hypertension among inhabitants of Tibet. The socioeconomic status of the inhabitants can influence awareness and management of hypertension. Very little research into hypertension has been conducted in other prefectures of Tibet where the altitude is much higher. Further research examining the impact of altitude on blood pressure is warranted.