Objectives: The purpose of this cross-sectional study was to determine the predictive value of measuring awake blood pressure (BP) at different time points on nocturnal hypertension by ambulatory blood pressure monitoring (ABPM) device in patients with hypertension.

Methods: A total of 558 consecutive hypertensive outpatients seeking medical care at the First Affiliated Hospital of Fujian Medical University from April 2023 to July 2024 were enrolled. We measured office BP and out-of-office BP. Out-of-office BP include evening BP, bedtime BP, morning BP and mean morning BP which were measured by ABPM device and BP daily record. Nocturnal hypertension was defined by the mean nocturnal blood pressure ≥120/70 mmHg (1 mmHg=0.133 kPa). ROC curve analyses of different awake blood pressure was established to identify significant correlates to nocturnal hypertension. The serial test was also performed. The value of the two indexes in predicting nocturnal hypertension was compared. The predictors of nocturnal hypertension were evaluated by multivariate analysis.

Results: Of the 558 subjects, 281 (50.4%) had nocturnal hypertension. Nocturnal hypertension was present in 76.9% (259/337) of patients with bedtime systolic BP ≥120 mmHg, in 94.6% (139/147) of patients with bedtime systolic BP ≥135 mmHg and in 86.8% (184/212) of patients with mean morning systolic BP ≥135 mmHg. ROC curve analyses showed that the diagnostic accuracy of bedtime systolic BP (AUC 0.907, P<0.05) for subjects with nocturnal hypertension was significantly superior to that of office systolic BP (AUC 0.739, P<0.05), evening systolic BP (AUC 0.808, P<0.05), morning systolic BP (AUC 0.859, P<0.05), and mean morning BP (AUC 0.876, P<0.05). Multivariate logistic regression analysis revealed that mean morning systolic BP and bedtime systolic BP were significantly associated with a higher risk of nocturnal hypertension (P<0.05). ROC curve analyses of predicted probability of bedtime systolic BP and mean morning systolic BP showed higher diagnostic accuracy (AUC 0.927, P<0.05).

Conclusions: Mean morning BP and bedtime BP are significant correlates of nocturnal hypertension in patients with hypertension, and combined mean morning BP with bedtime BP showed higher diagnostic accuracy, which might used for predicting nocturnal hypertension with high efficiency.