Abstract MP40: U-shaped Association Of Altitude With Prevalence Of Hypertension Among Tibetan Residents

Abstract

Background: Tibet has a disproportionately higher prevalence of hypertension, compared to other regions of China. This may be related to long-term exposure to the high altitude. The aim of our study is to evaluate associations of altitudes with prevalence of hypertension among residents aged 15 years and older in Tibet, China. Method: A total of 11,407 Tibet residents in the 5 th National Health Services Survey (NHSS) in 2013-2015 were included in this study. Physician diagnosed hypertension was determined based on self-report. County level altitude was identified and assigned to all residents in a county. Association between altitude and hypertension prevalence was assessed by two logistic regression models: model 1 adjusted for age and gender, and model 2 additionally adjusted for marital status, education, smoking, drinking, exercise, distance to a medical institute, area of residency, and body mass index (BMI). Non-linear relationship between altitude and prevalence of hypertension was explored by restricted cubic spline analyses. Sensitivity analysis were performed by restricting residents in rural and/or nomadic areas. Result: The prevalence of self-reported hypertension is 15.7%, the medication adherence rate is 14%, and the control rate is 10.3%. Compared to residents without physician diagnosed hypertension, those with hypertension were closer to a hospital, older, having lower education level, and less likely to be a smoker or live in an urban area. Altitude showed a U shape relationship with the prevalence of hypertension with a turning point at around 3,800 meters. For residents living more than 3,800 meters above sea level, a 1,000 meters increase in altitude was associated with 2.05 (95% confidence interval: 1.62-2.61) times higher odds of having physician diagnosed hypertension, after adjusting for age and gender. When further controlling for all covariates, the OR dropped to 1.87 (1.46-2.41) but still significant. For residents living below the altitude of 3,800 meters, 1000 meters’ increase was associated 0.55 (95% CI: 0.33-0.92) less likelihood of having physician diagnosed hypertension. Conclusion: The burden of self-reported hypertension was high among Tibet residents. Altitude was in a U-shaped association with the prevalence of hypertension with a turning point at around 3,800 meters.