Sleep assessment using a passive ballistocardiography-based system: preliminary validation

Quantitative sleep analysis through the use of polysomnography is a well established standard. Finding new ways to approach this, especially over multiple nights, is becoming more important due to a growing recognition of adverse effects from poor sleep and sleep disorders. The Non-Invasive Analysis of Physiological Signals (NAPS) system is a ballistocardiography-based monitoring system developed to measure heart rate, breathing rate and musculoskeletal movement that shows promise as a general sleep analysis tool. Overnight sleep studies were conducted on 20 healthy subjects during a validation clinical trial which compared the NAPS system to actigraphy, using polysomnography as the gold standard. The NAPS system [kappa=0.478; 95% CI (0.463, 0.494); p-value<0.001] outperformed actigraphy [kappa=0.344; 95% CI (0.324, 0.358); p-value<0.001], largely due to better performance in distinguishing sleep onset times as determined by polysomnography [NAPS mean bias estimate: -2.5 epochs; 95% CI (-16.8, 11.9); p=0.725|Actigraphy mean bias estimate: -33.6 epochs; 95% CI (-57.4, -9.7); p=0.016)].