Systems and methods for monitoring a subject for sleep apnea risk based on a bradycardia burden are disclosed. A sleep apnea monitoring system comprises a risk stratification circuit configured to detect bradycardia using cardiac information of the subject during a monitoring period, determine a bradycardia burden representing accumulated time or relative time of the subject being in the detected bradycardia over the monitoring period, and determine an apnea risk based on the bradycardia burden. An output unit can provide the apnea risk to a user, or to a process executed by an apnea detector to perform a confirmatory apnea detection.