Brain and Heart Rhythm Responses to a Breathing-Linked Sound Application (BELL-001) in Adults With Insomnia Symptoms

The purpose of this study was to describe how brain activity and heart rhythm respond to BELL-001, a smartphone application that plays sounds linked to the user\'s own breathing, compared with a sham application that looks the same but does not link its sounds to breathing. Adults with self-reported insomnia symptoms were randomly assigned to BELL-001 or to the sham application. During one laboratory visit, brain activity was recorded with electroencephalography (EEG), heart activity with electrocardiography (ECG), and breathing with a chest belt while participants rested with their eyes closed, then used the assigned application actively for 10 minutes, and then listened passively for 50 minutes. After the visit, all participants, regardless of laboratory group, used the BELL-001 application at home for 7 nights in an open-label period while wearing a smartwatch.