Sleep determination device and sleep determination method

Abstract

A sleep determination device that can accurately determine a REM sleep period during a sleep period without performing frequency analysis. [Solution] The system includes a data collection unit (S11) that collects heart rate data representing the heart rate per unit time during the subject's sleep period; a first calculation unit (S12) that treats the collected heart rate data during the sleep period as time series data and calculates a predicted trend value for each specified time period from the time series data as an hourly predicted trend value; a second calculation unit (S13) that calculates a trend value throughout the sleep period from the time series data as a period trend value; a third calculation unit (S14) that calculates the difference between the hourly trend value and the period trend value as an hourly sleep depth predicted value for each specified time period; and a REM determination unit (S16) that determines the REM sleep period during the sleep period based on the hourly sleep depth predicted value.

Description

[Technical Field]

[0001] The present invention relates to a sleep determination device and method for determining a REM sleep period during a sleep period based on the transition of a subject's heartbeat. [Background technology]

[0002] A sleep stage determination device described in Patent Document 1 is known. This sleep stage determination device has a biosensor (pressure sensor) that is attached to a mat on which a subject lies and outputs a signal corresponding to the subject's pressure against the mat. The sleep stage determination device extracts a heartbeat signal that varies in response to heartbeat from the body signals output from the biosensor, which vary in response to various body movements (heartbeat, respiratory movement, and body movement), converts the extracted signal into data, and generates the data as heartbeat data. The sleep stage determination device performs frequency analysis (FFT: Fast Fourier Transform) on the heartbeat data to convert it into frequency domain components, extracts frequency components from the frequency domain components in a range spanning a period of 2.5 seconds to 150 minutes (mid-frequency components), and converts the extracted frequency components into time domain data (IFFT: Inverse Fourier Transform). The sleep stage determination device then determines that a time domain exceeding a predetermined threshold in the time domain data is a REM sleep stage.

[0003] Such a sleep stage determination device can determine the REM sleep period within a sleep period without attaching electrodes or the like to the subject and restraining them on a bed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-164397 Summary of the Invention [Problem to be solved by the invention]

[0005] The sleep stage determination device described above converts heart rate data (time domain data) into frequency components (FFT: Fast Fourier Transform), and then inversely transforms the frequency domain data (IFFT: Inverse Fourier Transform) to return it to time domain data. Converting heart rate data into frequency components (frequency analysis) in this way assumes that a certain wave is repeated, and does not necessarily capture the actual state of the heartbeat, which includes complex level fluctuations, periodic fluctuations, etc., during sleep. Therefore, conventional sleep stage determination devices that use such frequency analysis processing have limitations in their detection accuracy.

[0006] The present invention has been made in consideration of the above circumstances, and provides a sleep determination device and a sleep determination method that can accurately determine the REM sleep period during a sleep period without performing frequency analysis. [Means for solving the problem]

[0007] The sleep determination device according to the present invention includes a data collection unit that collects heart rate data representing the heart rate per unit time during a sleep period of a subject; a first calculation unit that treats the collected heart rate data during the sleep period as time-series data and calculates a predicted trend value for each predetermined time period from the time-series data as an hourly predicted trend value; a second calculation unit that calculates a trend value throughout the sleep period from the time-series data as a period trend value; a third calculation unit that calculates a difference between the hourly predicted trend value calculated by the first calculation unit and the period trend value calculated by the second calculation unit as an hourly sleep depth predicted value for each predetermined time period; and a REM determination unit that determines a REM sleep period during the sleep period based on the hourly sleep depth predicted value calculated by the third calculation unit.

[0008] With this configuration, heart rate data representing the heart rate per unit time during a sleep period of a subject is collected. The collected heart rate data during the sleep period is treated as time-series data, and a predicted trend value for each predetermined time period is calculated from the time-series data as an hourly predicted trend value. Furthermore, a trend value throughout the sleep period is calculated from the time-series data of the heart rate data during the sleep period as a periodic trend value. The difference between the hourly predicted trend value and the periodic trend value is then calculated as an hourly sleep depth predicted value, and REM sleep periods during the sleep period are determined based on the hourly sleep depth predicted value.

[0009] In the sleep determination device of the present invention, the REM determination unit may include a comparison determination unit that determines whether the hourly sleep depth prediction value is greater than a predetermined threshold, and based on the determination result of the comparison determination unit, determines a period in which the hourly sleep depth prediction value is greater than the threshold as a REM sleep period.

[0010] With this configuration, it is determined whether the hourly sleep depth predicted value, which is the difference between the hourly predicted trend value and the period trend value, is greater than a predetermined threshold, and a period during which the hourly sleep depth predicted value is greater than the predetermined threshold, i.e., a period during which the trend of the heart rate estimated for each predetermined period (which can be represented by the hourly predicted trend value) is greater than the trend of the heart rate throughout the entire sleep period (which can be represented by the period trend value) by more than a certain amount (predetermined threshold), is determined to be a REM sleep period.

[0011] The hourly predicted trend value μ t is the time series data of heart rate y t from, μ t =μ t-1 +δ t-1 δ t =δ t-1 +ζ t ζ t ~Normarl(0,σ 2 ζ ) δ t : First difference at time t (μt -μ t-1 ) size ζ t : Regular white noise According to Under the following assumptions, δ t The likelihood of t ~Normal(δ t-1 , σ 2 ζ ) Heart rate value t The likelihood of y t ~Normal(μ t , δ 2 v ) It can be calculated by repeated calculations.

[0012] The aforementioned period trend value Y t is calculated using the following matrices X and θ: X: 1 each row, y t , y t 2 θ:[c, b, a] T where T is the transpose, a, b, c: parameters (X T X)θ=X T Y t can be calculated for each time t using θ calculated by the least squares method.

[0013] The sleep determination method of the present invention includes a data collection step of collecting heart rate data representing the heart rate per unit time during a sleep period of a subject; a first calculation step of treating the collected heart rate data during the sleep period as time series data and calculating a predicted trend value for each predetermined time period from the time series data as an hourly predicted trend value; a second calculation step of calculating a trend value throughout the sleep period as a period trend value from the time series data; a third calculation step of calculating a difference between the hourly predicted trend value calculated in the first calculation step and the period trend value calculated in the second calculation step as an hourly sleep depth predicted value for each predetermined time period; and a REM determination step of determining a REM sleep period during the sleep period based on the hourly sleep depth predicted value calculated in the third calculation step.

[0014] In addition, in the sleep determination method of the present invention, the REM determination step can include a comparison determination step of determining whether the hourly sleep depth predicted value is greater than a predetermined threshold, and based on the determination result in the comparison determination step, a period during which the hourly sleep depth predicted value is greater than the threshold can be determined to be a REM sleep period. [Effects of the Invention]

[0015] The sleep determination device and sleep determination method according to the present invention can accurately determine the REM sleep period within a sleep period without performing frequency analysis. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a block diagram showing a sleep determination device according to the present invention. [Figure 2] FIG. 2 is a graph showing the progress of heart rate data representing the heart rate per minute. [Figure 3] 2 is a flowchart showing a processing flow in a sleep stage determination unit in the sleep determination device shown in FIG. [Figure 4] FIG. 4 is a graph showing the transition of the hourly predicted trend value μt obtained based on the heart rate data during the sleeping period. [Figure 5] FIG. 5 is a diagram showing a comparison between (a) the determination result of the REM sleep period obtained from the hourly sleep depth prediction value and (b) the sleep stage determination result based on sleep depth estimation by an electroencephalograph. [Figure 6] FIG. 6 is a diagram showing numerical values ​​of the REM sleep determination result in the embodiment of the present invention and the REM sleep determination result based on sleep depth estimation by an electroencephalograph. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0018] A sleep determining device according to an embodiment of the present invention is configured as shown in FIG.

[0019] 1, the sleep determination device includes a sensor pad 60 provided on a bed 50 and an information processing device 10 such as a personal computer. A subject S (person) lies on the bed 50 with their back pressing against the sensor pad 60. A sensor (piezoelectric element) is provided within the sensor pad 60, and a detection signal corresponding to the movement (vibration) of the subject S transmitted to the sensor through the sensor pad 60 is output from the sensor (piezoelectric element).

[0020] The information processing device 10 is a computer configured with hardware and software, and includes a biosignal processing unit 11, a storage unit 12, and a sleep stage determination unit 13. The biosignal processing unit 11 receives a detection signal from a sensor (piezoelectric element) in a sensor pad 60, which changes in response to the subject S's body movements (body movements such as turning over in bed, breathing, and heartbeat). The biosignal processing unit 11 extracts a heartbeat signal whose level changes in response to the heartbeat by performing impedance conversion and filtering on the detection signal from the sensor pad 60 (sensor). The biosignal processing unit 11 then generates heartbeat data representing the number of heartbeats per unit time, for example, per minute, from the heartbeat signal. The heartbeat data (heartbeats / minute) over a predetermined time period, including a sleep period, changes, for example, as shown in FIG. 2. The biosignal processing unit 11 stores the heartbeat data (heartbeats / minute) over the predetermined time period, including a sleep period, in the storage unit 12.

[0021] The sleep stage determination unit 13 determines the REM sleep period during the sleep period using the heart rate data (heart rate / minute) stored in the storage unit 12. Specifically, the sleep stage determination unit 13 performs processing according to the procedure shown in FIG.

[0022] 3, the sleep stage determination unit 13 acquires heart rate data during the sleep period (from the start of sleep to the time of waking up) from the storage unit 12 (S11: data collection unit (data collection step)). t is used as time series data, and a predicted trend value for each predetermined time, for example, every minute, is calculated from the time series data as an hourly predicted trend value μ t (S12: first calculation unit (first calculation step)). t can represent the trend of the estimated heart rate for each predetermined period, for example, for each minute, without being affected by heart rate fluctuations (periods) that are less than twice the predetermined period (1 minute).

[0023] Hourly predicted trend value μ t Specifically, μ t =μ t-1 +δ t-1 δt =δ t-1 +ζ t ζ t ~Normarl(0,σ 2 ζ ) δ t : First difference at time t (μ t -μ t-1 ) size ζ t : Regular white noise According to Under the following assumptions, δ t The likelihood of t ~Normal(δ t-1 , σ 2 ζ ) Heart rate value t The likelihood of y t ~Normal(μ t , δ 2 v ) It can be calculated by repeated calculations.

[0024] As a result of the above calculation, for example, the heart rate data y t (Time series data) shows the hourly predicted trend value μ t can be obtained.

[0025] Next, the sleep stage determination unit 13 calculates a trend value throughout the sleep period from the time series data (heart rate data) as a period trend value Y t (S13: second calculation unit (second calculation step)). t can represent the trend of heart rate throughout the sleep period without being affected by heart rate variability (cycles) beyond the sleep period. Period trend value Y t is calculated using the following matrices X and θ: X: 1 each row, y t , y t 2 θ:[c, b, a] T However, T is transpose a, b, c: parameters (X T X)θ=X T Y t It can be calculated for each time t using θ calculated by the least squares method from

[0026] The sleep stage determination unit 13 calculates the hourly predicted trend value μ t (See S12) and the period trend value Y t The difference between (μ t -Y t ) as an hourly sleep depth predicted value for each minute (S14: third calculation unit (third calculation step)). Then, the sleep stage determination unit 13 calculates the hourly sleep depth predicted value (μ t -Y t ) to determine the REM sleep period during the sleep period (REM determination unit, REM determination step).

[0027] The REM sleep period is determined as follows (S15 to S20).

[0028] The sleep stage determination unit 13 determines the start time t of the sleep period at t. start (S15), and at that time t start Hourly sleep depth prediction value (μt start -Yt start ) is greater than a predetermined threshold value TH (S16: comparison and determination unit (comparison and determination step) and REM determination unit (REM determination step)). start ) is greater than the threshold TH (μt start -Yt start >TH:S16 YES), at that point t start is determined to be a REM sleep period Rem (S17). start -Yt start ) is below the threshold TH (μt start -Yt start ≦TH: NO in S16), the sleep stage determination unit 13 determines whether the sleep stage is start is determined to be not a REM sleep period (NonRem) (S18).

[0029] Thereafter, the sleep stage determination unit 13 determines whether t is the end point t of the sleep period. end (NO in S19), and while incrementing t by 1 minute (1 min) (t = t + 1 min: S20), the hourly sleep depth prediction value (μ t -Y t ) is greater than the threshold value TH (S16: comparison / determination unit / REM determination unit). t -Y t ) is greater than the threshold TH (μ t -Y t >TH: YES in S16, the time point t is determined to be the REM sleep period Rem (S17), while the hourly sleep depth predicted value (μ t -Y t ) is below the threshold TH (μ t -Y t ≦TH: NO in S16), the time point t is determined to be not a REM sleep period (NonRem) (S18).

[0030] In the process described above, t is updated every minute until the end of the sleep period t end When the result of S19 is YES, the sleep stage determination section 13 ends the series of processes.

[0031] As a result of the above-described processing, the hourly sleep depth prediction value (μ t -Y t ) is obtained, and its hourly sleep depth prediction value (μ t -Y t ) and the threshold TH (μ t -Y t >TH), periods T1, T2, T3, T4, and T5 during the sleep period are determined to be REM sleep periods. This determination result roughly coincides with the sleep depth estimation result (depth 4) using an electroencephalograph shown in Figure 5(b). In Figure 5(b), W represents wakefulness, depth 4 represents REM sleep, and depths 3 to 0 represent non-REM sleep.

[0032] Furthermore, the estimation results (Example) by the above-described processing and the sleep depth estimation results by the electroencephalograph are numerically compared as shown in Figure 6. In Figure 6, the sleep depth estimation results by the electroencephalograph estimated 87 out of 355 time points (a sleep period of 5 hours and 55 minutes) to be REM sleep periods (Rem), whereas the determination results (Example) by the above-described processing estimated 84 out of 355 time points to be REM sleep periods (Rem) (accuracy rate = 96.6%). Furthermore, the sleep depth estimation results by the electroencephalograph estimated 244 out of 355 time points to be non-REM sleep periods (NonRem), whereas the determination results (Example) by the above-described processing estimated 229 out of 355 time points to be non-REM sleep periods (NonRem) (accuracy rate = 93.9%).

[0033] According to the sleep determining device according to the embodiment of the present invention as described above, it is possible to accurately determine the REM sleep period within the sleep period without performing frequency analysis.

[0034] In the above-described process, the threshold value TH used in determining the REM sleep period (see S16 in FIG. 4) can be determined to an appropriate value based on, for example, the sleep depth determination result obtained by an electroencephalograph.

[0035] In the above-described process, the heart rate data represents the heart rate per minute, but the heart rate data may represent the heart rate per predetermined time other than one minute. t The hourly sleep depth predicted value may also represent values ​​(predicted trend value, predicted sleep depth value) for each predetermined time period other than one minute.

[0036] Hourly predicted trend value μ t is obtained by repeated calculations according to the above-mentioned formula, but is not limited to this, and a trend value representing the tendency of the heart rate may be obtained according to another calculation method every predetermined period, for example every minute.

[0037] Also, the period trend value Yt was obtained by calculation according to the above-mentioned formula, but is not limited to this, and a trend value representing the tendency of the heart rate throughout the sleep period may be obtained according to other calculation methods.

[0038] Although the embodiments of the present invention have been described above, these embodiments are presented by way of example only and are not intended to limit the scope of the invention. The novel embodiments described above can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments are included within the scope and spirit of the invention, and are also included in the invention described in the claims. [Industrial Applicability]

[0039] The sleep determination device and sleep determination method of the present invention have the advantage of being able to accurately determine the REM sleep period during a sleep period without performing frequency analysis, and are useful as a device and method for determining the REM sleep period during a sleep period based on the subject's heartbeat. [Explanation of symbols]

[0040] 10. Information processing equipment 11. Biological signal processing section 12 Storage section 13 Sleep stage determination unit 50 beds 60 Sensor Pad

Claims

1. a data collection unit that collects heart rate data representing the heart rate per unit time during the subject's sleep period; a first calculation unit that calculates a predicted trend value for each predetermined time period from the collected heart rate data during the sleep period as time series data, as an hourly predicted trend value; a second calculation unit that calculates a trend value throughout the sleep period from the time series data as a period trend value; a third calculation unit that calculates a difference between the hourly trend value calculated by the first calculation unit and the period trend value calculated by the second calculation unit as an hourly sleep depth predicted value for each predetermined time period; a REM determination unit that determines a REM sleep period within the sleep period based on the hourly sleep depth predicted value calculated by the third calculation unit.

2. The REM determination unit a comparison / determination unit that determines whether the hourly sleep depth predicted value is greater than a predetermined threshold value; The sleep determining device according to claim 1 , wherein a period in which the hourly sleep depth predicted value is greater than the threshold value is determined as a REM sleep period based on the determination result of the comparison / determination unit.

3. The first calculation unit calculates time series data y ｔ From the hourly predicted trend value μ ｔ of m ｔ =μ ｔ－１ +d ｔ－１ d ｔ =d ｔ－１ +g ｔ g t ~Normarl(0,σ ２ ζ ) σ ｔ : First difference at time t (μ ｔ -μ ｔ－１ ) size ζ ｔ : Regular white noise According to Under the following assumptions, δ ｔ The likelihood of ｔ ~Normal (δ ｔ－１ , σ ２ ζ ) Heart rate value y ｔ The likelihood of ｔ ~Normal(μ ｔ , δ ２ ｖ ) 3. The sleep determining device according to claim 1, wherein the calculation is performed by repeated calculation.

4. The second calculation unit uses the following matrices X and θ: X: Each row 1, y ｔ y ｔ ２ θ: [c, b, a] Ｔ T is transpose a, b, c: parameters The period trend value Y ｔ , and the following equation (X Ｔ X)θ=X Ｔ Y ｔ 4. The sleep determining device according to claim 3, wherein the sleep determining device calculates the sleep time t for each time t using θ calculated by the least squares method from the above.

5. a data collection step of collecting heart rate data representing the number of heart rates per unit time during the subject's sleep period; a first calculation step of treating the collected heart rate data during the sleep period as time-series data and calculating a predicted trend value for each predetermined time period from the time-series data as an hourly predicted trend value; a second calculation step of calculating a trend value throughout the sleep period from the time series data as a period trend value; a third calculation step of calculating a difference between the hourly predicted trend value calculated in the first calculation step and the period trend value calculated in the second calculation step as an hourly sleep depth predicted value for each predetermined time period; a REM determination step of determining a REM sleep period within the sleep period based on the hourly sleep depth prediction level calculated in the third calculation step.

6. The REM determination step includes: a comparison step of determining whether the hourly sleep depth prediction value is greater than a predetermined threshold value; 6. The sleep determining method according to claim 5, further comprising determining, based on the determination result in the comparing and determining step, a period in which the hourly sleep depth predicted value is greater than the threshold value as a REM sleep period.

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