Hypertension and altitude in community-dwelling older adults: an epidemiological study in northwest China

Objectives Hypertension is a major risk factor for cardiovascular and cerebrovascular diseases, and a relationship between altitude and hypertension has been demonstrated. To better characterise this relationship, this study investigated the prevalence of hypertension and its association with altitude in community-dwelling older adults living at different altitudes in Xinjiang, northwest China. Design A cross-sectional study. Setting Xinjiang, China. Participants 50 778 community-dwelling older adults residing at varying altitudes across Xinjiang. Measures A multistage stratified sampling method was used to conduct an epidemiological survey from January 2019 to December 2019 among 50 778 community-dwelling older adults aged ≥60 years who were long-term residents of Kashgar (1289 m), Hami (738 m) and Turpan (35 m), Xinjiang. Logistic regression analysis was conducted to evaluate the association between altitude and hypertension risk. Results Mean systolic blood pressure (SBP) and diastolic blood pressure (DBP) showed significant variations (both p<0.001) across Kashgar, Hami and Turpan at different altitudes: Kashgar (SBP: 133.15±19.644 mm Hg, DBP: 76.6±11.363 mm Hg), Hami (SBP: 136.68±19.617 mm Hg, DBP: 77.25±11.808 mm Hg) and Turpan (SBP: 135.44±21.101 mm Hg, DBP: 74.87±12.785 mm Hg). Statistically significant differences in the distributions of both SBP and DBP were observed across different altitudes for both males and females (all p<0.001). The differences in the distributions of SBP and DBP at different altitudes were statistically significant in all age groups, except for ≥90 years (all p<0.001). Moreover, the differences in SBP and DBP in older individuals living at the three altitudes were statistically significant (all p<0.001) regardless of smoking status, alcohol consumption, diabetes, education level or body mass index. The hypertension prevalence rates were 40.5%, 49.5% and 54.5% in Kashgar, Hami and Turpan, respectively (p<0.001). After adjustment for sex, age group, education level, smoking, alcohol consumption, BMI, diabetes, HR, SCr, blood urea nitrogen and dyslipidaemia, the risk of hypertension was increased in Hami (OR = 1.55, 95% CI 1.45 to 1.66, p<0.001) and Turpan (OR=1.80, 95% CI 1.71 to 1.88, p<0.001) compared with that in Kashgar. Conclusions In community-dwelling older adults residing in lowland to mid-elevation zones (35–1289 m) of Xinjiang, the prevalence and risk of hypertension were found to be inversely associated with residential altitude. These findings may reflect an environmental gradient effect specific to mid-to-low altitude settings, and their generalisability may be limited to populations at higher altitudes (>1500 m) or regions with distinct ethnic, genetic or healthcare backgrounds. Furthermore, it should be emphasised that this association likely reflects altitude-related environmental factors rather than direct physiological effects of hypoxia. Additional studies are warranted to further elucidate these complex relationships.