Heart rate variability with sleep detection
A system uses continuous tracking of sleep activity and heart rate activity to evaluate heart rate variability immediately before transitioning to an awake state, e.g., at the end of the last phase of deep sleep. In particular, a wearable, continuous physiological monitoring system as described herein includes one or more sensors to detect sleep states, the transitions between sleep states, and the transitions from a sleep state to an awake state for a user. This information can be used in conjunction with continuously monitored heart rate data to calculate heart rate variability of the user at the end of the last phase of sleep preceding the user waking up. By using the history of heart rate data in conjunction with sleep activity in this manner, an accurate and consistent recovery score can be calculated based on heart rate variability.
1. A method of operating a wearable, continuous physiological monitoring system comprising:
detecting a sleep state of a user;
monitoring a heart rate of the user substantially continuously with the continuous physiological monitoring system;
recording the heart rate as heart rate data;
detecting a waking event at a transition from the sleep state of the user to an awake state;
detecting a slow wave sleep period occurring most recently before the waking event;
evaluating a quality of heart rate data using a data quality metric for the slow wave sleep period;
calculating a heart rate variability for a window of predetermined duration within the slow wave sleep period having a highest quality of heart rate data according to the data quality metric; and
calculating a recovery score for the user based upon the heart rate variability.
2. The method of claim 1 further comprising calculating additional recovery scores after one or more other waking events of the user for comparison to the recovery score.
3. The method of claim 1 further calculating a duration of the sleep state and using the duration to calculate the recovery score.
4. The method of claim 1 further comprising detecting the sleep state using an accelerometer of the wearable, continuous physiological monitoring system.
5. The method of claim 4 further comprising detecting the waking event using the accelerometer.
6. The method of claim 1 further comprising detecting a galvanic skin response (GSR) of the user with the wearable, continuous physiological monitoring system and using the GSR to detect the sleep state.
7. The method of claim 1 further comprising detecting at least one of the sleep state and the waking event based upon the heart rate data.
8. The method of claim 1 wherein recording the heart rate data includes recording the heart rate data continuously without calculating the heart rate variability.
9. The method of claim 1 wherein the wearable, continuous physiological monitoring system includes a processor, one or more light emitting diodes, and one or more light detectors configured to obtain the heart rate data from the user.
10. The method of claim 1 further comprising calculating a sleep need score estimating an amount of sleep needed by the user in a next night, and communicating the sleep need score to user.
11. A system comprising:
a wearable housing;
one or more sensors in the wearable housing; and
a processor in the wearable housing, the processor configured to operate the one or more sensors to detect a sleep state of a user wearing the wearable housing, to monitor a heart rate of the user substantially continuously, to record the heart rate as heart rate data without calculating a heart rate variability for the user, to detect a waking event at a transition from the sleep state of the user to an awake state, to detect a slow wave sleep period occurring most recently before the waking event, to evaluate a quality of heart rate data using a data quality metric for the slow wave sleep period, to calculate the heart rate variability for a window of predetermined duration within the slow wave sleep period having a highest quality of heart rate data according to the data quality metric, and to calculate a recovery score for the user based upon the heart rate variability.
12. The system of claim 11 wherein the one or more sensors include a light detector configured to provide data to the processor for calculating the heart rate variability.
13. The system of claim 11 wherein the one or more sensors include an accelerometer configured to provide data to the processor for detecting the sleep state or the waking event.
14. The system of claim 11 further comprising a light source coupled to the housing and controlled by the processor, the light source directed toward a skin on an appendage of the user.
15. The system of claim 11 wherein the one or more sensors measure a galvanic skin response of the user.
16. A computer program product for operating a wearable, continuous physiological monitoring system, the computer program product comprising computer executable code embodied in a non-transitory computer readable medium that, when executing on the wearable, continuous physiological monitoring system, performs the steps of:
detecting a sleep state of a user;
monitoring a heart rate of the user substantially continuously with the continuous physiological monitoring system;
recording the heart rate as heart rate data;
detecting a waking event at a transition from the sleep state of the user to an awake state;
detecting a slow wave sleep period occurring most recently before the waking event;
evaluating a quality of heart rate data using a data quality metric for the slow wave sleep period;
calculating a heart rate variability using a window of heart rate data within the slow wave sleep period, wherein the window is selected based on the quality of heart rate data; and
calculating a recovery score for the user based upon the heart rate variability.
17. The computer program product of claim 16 further comprising code that performs the step of calculating a duration of the sleep state and using the duration to calculate the recovery score.
18. The computer program product of claim 16 further comprising code that performs the step of detecting at least one of the sleep state and the waking event using an accelerometer of the wearable, continuous physiological monitoring system.
19. The computer program product of claim 16 wherein the window of heart rate data includes a predetermined duration within the slow wave sleep period having a highest quality of heart rate data according to the data quality metric.