Determination of bed-time duration using wearable sensors

A system for automatically determining bed-time periods, the system comprising at least one sensor to detect a plurality of physiological signals, a processor coupled to the at least one sensor, and a memory device coupled to the processor, wherein the memory device includes an application that, when executed by the processor, causes the processor to:

• determine a posture angle and an activity level using at least one of the plurality of detected physiological signals;
• and
• determine a bed-time period using both the posture angle and the activity level, wherein the determining the bed-time period comprises:
• determining a bed-entry event, and
• determining a bed-exit event;
• wherein the determining the bed-entry event and the bed-exit event comprises:
• determining whether a fraction of the supine posture over a slower moving window (FSPSMW) is greater than a first threshold,
• in response to the FSPSMW being greater than the first threshold, determining whether a fraction of the supine posture over a faster moving window (FSPFMW) is greater than a second threshold, wherein if both FSPSMW is greater than the first threshold and FSPFMW is greater than the second threshold, the bed-entry event is determined for a given data sample number, and
• in response to the FSPSMW being less than or equal to the first threshold, determining whether a fraction of the supine posture over a faster moving window (FSPFMW) is less than the second threshold, wherein if FSPSMW is less than or equal to the first threshold and FSPFMW is less than the second threshold, the bed-exit event is determined for the given data sample number;
• and
• wherein the bed-time period is a time difference between the bed-exit event and the bed-entry event.