O56 NIGHTTIME BLOOD PRESSURE REFERENCE VALUES FOR AMBULATORY BLOOD PRESSURE MONITORING AND THEIR RELATIONSHIP WITH AGE

Background and Objective: Nocturnal hypertension is characterized by elevated blood pressure (BP) levels during sleep (systolic blood pressure [SBP]>120 mmHg or diastolic blood pressure [DBP]>70 mmHg) as measured by 24-hour ambulatory blood pressure monitoring (24-h ABPM) (ESH 2023 guidelines). With aging, there is a gradual decline in renal function and vascular health, leading to changes in BP patterns. This study seeks to evaluate the necessity of age-specific cutoff points in defining hypertension, particularly during nocturnal hours. Methods: A cross-sectional study was conducted, involving 3,220 patients without hypertension, defined by 24-hour BP values, who were not using any antihypertensive medications and were referred for 24-h ABPM. Patients with a body mass index (BMI) ≥30 kg/m 2 were excluded. The sleep period was defined as spanning from midnight to 6 am. Reference percentiles were established and juxtaposed with standard references. To determine the significance of age-specific cutoff points for defining nocturnal hypertension, the ESH 2023 reference was compared with the 95th percentile (P95) for age. Results: Among the participants, 64.6% were female, with an average age of 51.0±15.0 years, BMI of 25.0±2.7 kg/m 2 , nocturnal SBP of 106.4±9.0 mmHg (P95=121.8 mmHg), and nocturnal DBP of 66.0±5.0 mmHg (P95=74.3 mmHg). Normal distribution was observed for both SBP and DBP (Jarque Bera test). Nocturnal SBP exhibited a “J” shaped curve concerning age, whereas the average DBP remained relatively stable. Significant differences were noted for SBP across different age groups (P value <0.00001). Proposed cutoff points for mean nocturnal SBP were suggested as follows: i) P95 <60 years=120 mmHg; ii) P95 60-70 years=125 mmHg; and iii) P95 >70 years=130 mmHg (Figure). A reference of 75 mmHg was proposed as the cutoff point for mean nocturnal DBP. Conclusions: The study highlights age-related variations in the P95 of mean nocturnal SBP, while DBP remains relatively stable across age groups. Consequently, we propose new cutoff points for defining these parameters.