Study on the ambulatory blood pressure phenotype and its correlation with hemoglobin concentration in untreated hypertensive individuals permanently living in plateau areas.

Ambulatory blood pressure monitoring (ABPM) studies for high altitude (HA) hypertensive patients are limited. We aimed to explore the hypertension phenotypes, and investigate their associations with hemoglobin in untreated hypertensives permanently living in HA. A total of 342 untreated hypertensive patients were included. Among the whole population, 91.80% had sustained hypertension (SH). In patients with SH, the proportions of isolated daytime hypertension, isolated nocturnal hypertension, and day-night hypertension were 2.87%, 2.87%, and 94.26%, respectively. Compared to patients with hemoglobin ≥16 g/dL, those with hemoglobin <16 g/dL had higher nocturnal average systolic blood pressure (SBP) (140.33 ± 17.46 vs. 136.26 ± 17.55 mmHg, P = 0.03) and a greater proportion of patients with nocturnal SBP fall<10% (55.00% vs. 43.30%, P = 0.03). Bivariate correlation analysis showed that hemoglobin was negatively correlated with the nocturnal average SBP (r = -0.145, P < 0.01) and was positively related to the nocturnal SBP fall (r = 0.136, P = 0.01). We found that the threshold effect value between hemoglobin and nocturnal blood pressure indices was 16 g/dL. The effect value between hemoglobin and nocturnal average SBP was -3.60 (-5.46, -1.74) for hemoglobin <16 g/dL and 0.88 (-1.07, 2.83) for hemoglobin ≥16 g/dL. Correspondingly, the effect values between hemoglobin and nocturnal SBP fall were 1.53 (0.61, 2.45) and -0.26 (-1.23, 0.70). In addition, hemoglobin was independently correlated with the above-mentioned nocturnal blood pressure indices in those with hemoglobin <16 g/dL. In conclusion, nocturnal hypertension was a prevalent ABPM phenotype in HA hypertensive patients. In those with hemoglobin levels <16 g/dL, hemoglobin concentration shows a significant inverse correlation with nocturnal SBP, suggesting that lower hemoglobin levels may warrant enhanced evaluation of nocturnal BP in this population.