THE IMPACT OF BODY POSTURE ON NOCTURNAL BLOOD PRESSURE AND DIPPING PATTERNS: THE ROLE OF HYDROSTATIC PRESSURE

Objective: Nocturnal blood pressure (BP) is a key predictor of cardiovascular events, yet individual dipping patterns show poor reproducibility. We hypothesize that positional changes during sleep lead to variations in hydrostatic pressure, resulting in inaccuracies in BP measurements.Design and method: A total of 51 participants (26 aged 18–30 years; 25 aged 50 years and older) underwent ambulatory BP monitoring on the left arm. Simultaneously, the hydrostatic pressure difference between the BP cuff and heart level was calculated during each measurement. Results: On average, the BP cuff was positioned above heart level throughout the night, leading to negative hydrostatic pressure. Right-side sleeping caused the largest hydrostatic pressure discrepancy and the most significant measurement error, averaging -9.61 mmHg during sleep. Adjusting for hydrostatic pressure reclassified nocturnal hypertension in 14 participants (27.5%) and altered dipping patterns in 19 participants (37.3%). Overall, 25 participants (49.0%) experienced changes in either their nocturnal hypertension status or dipping classification. Conclusions: These findings highlight the critical role of hydrostatic pressure in ambulatory BP monitoring. Body position during sleep is a plausible source of variability in nocturnal dipping patterns. Future efforts should focus on integrating hydrostatic pressure correction mechanisms into 24-hour BP monitoring to enhance the accuracy of hypertension diagnosis, classification, and treatment.