Tracking Nocturnal Blood Pressure Dipping With the Aktiia Cuffless Monitor

Objective: Previous studies have highlighted the prognostic importance of night-time blood pressure (BP) dipping, associating non-dipping BP patterns with cardiovascular risk. Standard 24-h ambulatory BP monitors (ABPM) often show inconsistent reproducibility in nocturnal dipping. Cuffless BP monitors present a promising approach for continual measurement of night-time BP, yet their effectiveness is to be assessed. This study compares nocturnal BP dipping as recorded by a cuffless BP monitor with readings from a conventional 24-h ABPM. Design and method: 63 subjects (NCT04548986, mean age 53.1±7.2 years, 21.2% female, arm circumference 29.0±2.5 cm) were enrolled in a 12-week cardiac rehabilitation program at RHNE – Réseau Hospitalier Neuchâtelois, Switzerland. Systolic BP (SBP) night-time dipping was assessed by comparing same-day daytime (9am–9pm) and night-time (11pm–7am) averages using both cuffless BP monitor (Aktiia SA, Switzerland) and ABPM (Dyasis 3, Novacor, France). Two sessions were analyzed: session 1 compared first day's ABPM and Aktiia data; session 2 compared final day's readings from both devices. Only sessions with >=20 daytime and >=7 night-time measurements for ABPM, and >=12 daytime and >=8 night-time measurements for Aktiia were considered for analysis. The performance of night dipping identification was evaluated as the area under the curve (AUC) of a Receiver Operating Characteristic (ROC) curve (reference: -10% ABPM night-dip), and as the concordance rate (CR, accuracy) of a Four-Quadrant Plot (FQP, ±6% exclusion zone around -10% ABPM night dips). Results: 30 subjects fulfilled the data availability requirements per BP modality (26 in session 1, 12 in session 2). Figure 1A illustrates the ROC curve (AUC=0.72). The optimal operating point for Aktiia's night-time dip was found at -2.96% (red dot, 91% sensitivity, 63% specificity). Figure 1B shows the FQP comparing night-dips recorded by ABPM and Aktiia (78.9% CR, 83.3% precision). Conclusions: The Aktiia monitor effectively identifies nocturnal BP dipping with 78.9% accuracy, consistent with ABPM readings, despite some scaling differences. This indicates that the Aktiia monitor is sensitive to nocturnal BP dipping and holds potential for future use in continuous night-time monitoring. Further research is focused on improving nocturnal measurement accuracy.