O025 Impact of Temporal Rhythms on Blood Pressure Variability: Daily, Weekly, and Seasonal Effects

Abstract Introduction High blood pressure (BP) and BP variability are associated with increased risk of cardiovascular events and mortality. Despite known impacts of daily, weekly, and seasonal fluctuations on BP and BP variability, the independent temporal impacts are not well quantified, particularly in sleep research. Methods Participants comprised users of the Withings Sleep Analyzer and home blood pressure monitors, with ≥6 months of measurements, ≥3 times/week and at 3 unique hours of the day. Mixed models tested non-linear associations between mean-arterial pressure (MAP) and hour of the day, day of the week, and hemisphere-adjusted month of the year, adjusting for wake time, sleep duration, apnea-hypopnea index, age, and sex. Results Results included 40,332 participants (mean±SD 59±12 years old, 87/13% male/female) with 9.5 million BP measurements (median[IQR]=97[43,245] measurements per participant). MAP was independently associated with time since wake (range=1.14mmHg), peaking at wake and declining over the day, and the hour of the day (range=2.36mmHg), typically peaking at 6AM. Significant weekday (range=0.96mmHg) and monthly variability (range=2.14mmHg) resulted in the highest MAP on Monday, in winter months. The greatest variation, Monday morning in winter vs Friday evening in summer, accounted for a 6.69±0.08mmHg difference in MAP. Conclusion Measured BP varied considerably by time of day, day of week, and season, independently from sleep duration and timing. The significant variability imposed by these rhythms has important clinical implications. Without accounting for this temporal aspect, measurements of BP changes due to external factors like sleep disorders or treatment interventions could yield misleading or incorrect associations.