Cardiac rhythm development: A wearable device index of risk for physical and mental illness in adolescence

The study examined cardiac rhythm development in 8,301 adolescents using Fitbit wearable device data across three research waves (at ages 12, 14, and 16 years). Researchers found that cardiac rhythm changes substantially during adolescence: average heart rate decreases, daily fluctuations flatten, and peak activity timing shifts later. Changes in individual cardiac rhythm correlated with changes in blood pressure, BMI, and symptoms of depression and ADHD. Higher average heart rate predicted the onset of all five studied conditions including psychiatric disorders, obesity, and hypertension. The research suggests that the 24-hour cardiac rhythm is a passively measurable indicator of autonomic nervous system development and signals risk for various psychiatric and cardiometabolic illnesses.