JP2016022276A - Sleep stage determination apparatus and sleep stage determination method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sleep stage determination apparatus that can determine a sleep stage with high accuracy by adopting a proper normalization technique.SOLUTION: A sleep stage determination apparatus includes: a normalization unit 6 for constantly controlling a peak value by performing a gain control to the detected heartbeat signal in the non-invasive and unconstraint manner with respect to a user's heartbeat signal, and for performing normalization about data of the heartbeat intensity calculated by using a value of the at that time; and a sleep stage determination unit 8 for determining the user's sleep stage based on a variance value showing the variations of data of the predetermined time calculated about the data of the normalized heartbeat intensity normalized by the normalization unit 6. The normalization unit 7 calculates moving average value of HinN=Hin*100/Hin as a normalized heartbeat intensity HinN, when the value of the gain obtained by the gain control is AGCr and the heartbeat signal intensity is Hin.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a sleep stage determination apparatus and a sleep stage determination method for determining a sleep stage from a heartbeat signal detected by a heartbeat signal detection means.

  Sleep is said to be a barometer of health, and if you can wake up comfortably by a comfortable sleep, you will feel refreshed when you wake up. On the other hand, in the case of insomnia or insomnia, or when forced to sleep with a reversed day / night life due to late-night work or the like, the mood after waking is often poor. That is, regardless of whether it is conscious or unconscious, the sleep state affects the mood and behavior at the time of subsequent awakening, which in turn determines the quality of the activity after the awakening.

  Thus, sleep is a factor that has an important influence on human physical activity and mental activity. If a good sleep can be obtained, healthy physical and mental activities are guaranteed. It's okay. It is known that if a comfortable sleep can be obtained, a mentally stable state can be obtained, and if it is mentally stable, a comfortable sleep can be obtained. Therefore, when investigating an individual's health condition, sleep is often used as a determination index, and it is well known that sleep and health are closely related. If the depth and quality of health and sleep are closely related to the mood and spirit of the next day, and mental stress and physical condition are poor, changes in sleep depth and transition patterns of sleep stages occur. Can't get a comfortable sleep.

  In healthy sleep, the REM sleep stage and the non-REM sleep stage appear repeatedly at predetermined intervals after falling asleep. ing. Therefore, it becomes possible to know the subject's mental stress and poor physical condition by monitoring the sleep stage and its occurrence pattern during nighttime sleep.

  In particular, many elderly people complain of poor sleep such as light sleep, and the quality of sleep is a problem. In order to know the quality of sleep, it becomes possible to find coping methods and measures that improve by knowing the transition of the sleep stage.

  Conventionally, as a method for knowing the sleep stage, a method using a sleep polysomnograph (PSG), which is an international criterion for sleep depth, is generally used. In the method using PSG, a lot of information related to sleep can be obtained by estimating the activity of the cranial nervous system during sleep from brain waves, surface myoelectric potential, eye movement, and the like.

  However, in the method using PSG, since many electrodes are attached to the subject's face and body for measurement, the subject feels a lot of discomfort, and it is difficult to obtain natural sleep. There is a problem that the mounting of the electrodes takes a lot of time and is extremely troublesome. In addition, in the method using PSG, the data for the first day measured in an environment different from normal sleep cannot be adopted as the first night effect, and the subject can be used for several days to one week before becoming accustomed to such an environment. There is a problem that it takes time. Therefore, since the physical and physical burdens given to the subject become very large, it is difficult to use continuously on a daily basis, and the measurement over several days is the limit. Furthermore, this measurement needs to be performed by an expert who is familiar with handling in a specific facility such as a hospital, and the equipment used for the measurement is expensive, so that the necessary cost is large. Therefore, PSG is not practical for a subject to use regularly in a hospital or at home, and even more difficult to use for daily health management, and thus can be an effective treatment for sleep disorders. On the other hand, there is a contradiction that it is difficult to apply to such patients.

  Therefore, a method for easily grasping the sleep stage without using PSG has been proposed. For example, a method of determining a sleep stage by measuring a heartbeat signal using a wristwatch type or a vibration intensity measuring device of a type laid on a futon is known.

  By the way, the amplitude (intensity) of the heartbeat signal varies depending on the user and the measuring device, and a difference between individuals and a difference depending on the measuring device occur. Therefore, in order to improve the accuracy of sleep stage determination by performing universal measurement, it is necessary to generalize the calculated heart rate signal intensity by eliminating individual differences and device differences, and it is desirable to normalize for this purpose. It is known (see, for example, Patent Document 1).

JP 2012-65853 A

  As described above, in order to determine the sleep stage by universal measurement, it is necessary to properly normalize the intensity of the heartbeat signal. However, in the conventional techniques including Patent Document 1, normalization is performed. No specific method for doing so was disclosed.

  The present invention has been made in view of such circumstances, and provides a sleep stage determination device and a sleep stage determination method that can determine a sleep stage with high accuracy by adopting an appropriate normalization method. The purpose is to do.

That is, the sleep stage determination apparatus according to the present invention that achieves the above-described object is the sleep stage determination apparatus that determines a user's sleep stage based on a heartbeat signal detected non-invasively and unconstrained during sleep. A heartbeat signal detecting means for detecting the heartbeat signal of the heartbeat signal non-invasively and unconstrained, and a peak value is controlled to be constant by performing gain control on the heartbeat signal detected by the heartbeat signal detecting means, and the gain at that time The normalization means for normalizing the intensity data of the heartbeat signal calculated using the value of, and the variation of the data for a predetermined time calculated for the normalized heartbeat intensity data normalized by the normalization means Sleep stage determining means for determining the sleep stage of the user based on a variance value, and the normalizing means is a gain value obtained by the gain control. And AGCR, when the strength of the heartbeat signal and Hin, as the normalized heart strength HinN,
The moving average value of HinN = Hin * 100 / Hin is calculated.

A sleep stage determination method according to the present invention that achieves the above-described object is a sleep stage determination method that determines a user's sleep stage based on a heartbeat signal detected non-invasively and unconstrained during sleep. A heartbeat signal detecting step for detecting the user's heartbeat signal noninvasively and unconstrained by the signal detection means, and a processor for performing signal processing performs gain control on the heartbeat signal detected in the heartbeat signal detection step. A normalization step of controlling the peak value to be constant by performing normalization on the heartbeat signal intensity data calculated using the gain value at that time, and the processor normalizing in the normalization step Sleep stage determination step of determining a sleep stage of the user based on a variance value indicating a variation in data of a predetermined time calculated for the normalized heart rate intensity data The provided, in the normalization step, when the a AGCr the resulting value of the gain by the gain control, and the strength of the heartbeat signal and Hin, as the normalized heart strength HinN,
The moving average value of HinN = Hin * 100 / Hin is calculated.

  Such a sleep stage determination apparatus and sleep stage determination method according to the present invention appropriately normalize the intensity data of the heartbeat signal detected non-invasively and unconstrained.

  In the present invention, since the normalization is performed on the intensity data of the heartbeat signal detected non-invasively and unconstrained, individual differences and apparatus differences can be eliminated, and as a result, the sleep stage is determined with high accuracy. be able to.

It is a figure which shows the structure of the sleep stage determination apparatus shown as embodiment of this invention. It is a figure which shows the structure of the sleep stage determination apparatus shown as embodiment of this invention, and is partial sectional drawing when it sees from the arrow direction in FIG. It is a figure which shows the time-sequential waveform of a heart rate intensity | strength. It is a figure which shows the time series waveform of the normalized heartbeat intensity | strength normalized about the waveform of FIG. It is a figure which shows the time series waveform of the dispersion | distribution value calculated | required about the waveform of FIG. It is a figure which shows the structure of another biological signal detection part.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings.

  This embodiment is a sleep stage determination device that determines a sleep stage. In particular, this sleep stage determination device realizes highly accurate sleep stage determination by performing appropriate normalization.

  FIG. 1 shows a configuration in which the process of the sleep stage determination device shown as an embodiment of the present invention is represented as a block, and FIG. That is, the sleep stage determination apparatus includes a biological signal detection unit 1 that detects a biological signal of a user lying on the bed 21 and a signal amplification unit 2 that amplifies the biological signal detected by the biological signal detection unit 1. A filtering unit 3 that performs a filtering process on the biological signal amplified by the signal amplification unit 2, and an automatic gain control unit 4 that automatically performs gain control on the heartbeat signal that has passed through the filtering unit 3. The signal strength calculation unit 5 that calculates the strength of the heart rate signal, the normalization unit 6 that normalizes the heart rate calculated by the signal strength calculation unit 5, and the normalized heart rate obtained by the normalization unit 6 And a sleep stage determination unit 8 that determines a user's sleep stage based on the dispersion value of the heart rate intensity calculated by the dispersion value calculation unit 7. Among these units, at least the signal intensity calculation unit 5, the normalization unit 6, the variance value calculation unit 7, and the sleep stage determination unit 8 include, for example, a CPU (Central Processing Unit) in a computer that performs signal processing, It can be implemented as a program executable using hardware such as a memory, or can be implemented using a dedicated processor such as a DSP (Digital Processing Unit) mounted on an expansion board that can be mounted on a computer.

  The biological signal detection unit 1 is a non-invasive and unconstrained sensor that detects a minute biological signal of a user. Specifically, the biological signal detection unit 1 includes a pressure detection tube 1a and a minute differential pressure sensor 1b that is a sensor that detects minute pressure fluctuations in the air accommodated in the pressure detection tube 1a. Thus, a non-invasive and non-constrained biological signal detection means is configured.

  As the pressure detection tube 1a, a tube having an appropriate elasticity so that the internal pressure fluctuates corresponding to the pressure fluctuation range of the biological signal is used. Further, as the pressure detection tube 1a, it is necessary to appropriately select the volume of the hollow portion of the tube in order to transmit the pressure change to the fine differential pressure sensor 1b at an appropriate response speed. When the pressure detection tube 1a cannot satisfy the appropriate elasticity and the volume of the hollow portion at the same time, the hollow portion of the pressure detection tube 1a is loaded with a core wire of an appropriate thickness over the entire length of the tube, and the volume of the hollow portion is set appropriately Can be taken.

  Such a pressure detection tube 1 a is disposed on a hard sheet 22 laid on the bed 21. In the sleep stage determination apparatus, an elastic cushion sheet 23 is laid on the hard sheet 22, and the user lies on the pressure detection tube 1a. Note that the pressure detection tube 1a may be configured to be incorporated in the cushion sheet 23 or the like to stabilize the position of the pressure detection tube 1a.

  The minute differential pressure sensor 1b is a sensor that detects minute fluctuations in pressure. In the present embodiment, a low-frequency condenser microphone type sensor is used as the fine differential pressure sensor 1b. However, the present invention is not limited to this, and any sensor having an appropriate resolution and dynamic range may be used. Good. The low-frequency condenser microphone used in the present embodiment is replaced with a general acoustic microphone that does not consider the low-frequency region, and a low-frequency region characteristic is provided by providing a chamber behind the pressure-receiving surface. Is significantly improved, and is suitable for detecting minute pressure fluctuations in the pressure detection tube 1a. In addition, this condenser microphone is excellent for measuring minute differential pressure, has a resolution of 0.2 Pa and a dynamic range of about 50 Pa, and is compared with a fine differential pressure sensor using a ceramic that is usually used. Therefore, it is suitable for detecting a minute pressure applied to the pressure detection tube 1a through a biological signal passing through the body surface. The frequency characteristic shows a substantially flat output value between 0.1 Hz and 30 Hz, and is suitable for detecting minute biological signals such as heartbeat and respiration.

  In the present embodiment, two sets of pressure detection tubes 1a are provided so that one detects a biological signal of the user's chest region and the other detects the user's buttocks region. A biological signal is detected regardless of the person's sleeping posture. In the sleep stage determination device, the pressure detection tube 1a may be arranged only in one of the chest region and the buttocks region. The biological signal detected by such a biological signal detection unit 1 is supplied to the signal amplification unit 2. By adopting such a non-invasive and non-constrained configuration for detecting a biological signal, the sleep stage determination device can be easily used in daily life, and is particularly suitable for the elderly.

  The signal amplification unit 2 amplifies the signal detected by the biological signal detection unit 1 so that it can be processed in a later processing step, and further performs an appropriate signal shaping process by removing a signal of an apparently abnormal level Do. The biological signal amplified by the signal amplifying unit 2 is supplied to the filter unit 3.

  The filter unit 3 extracts a heartbeat signal by removing unnecessary signals from the biological signal amplified by the signal amplification unit 2 using a band-pass filter or the like. That is, the biological signal detected by the biological signal detection unit 1 is a signal in which various vibrations emitted from the human body are mixed, and includes various signals such as a body motion signal due to turning over, in addition to a heartbeat signal. It is. Among these, the heartbeat signal is a signal in which a change in pressure (that is, blood pressure) based on the pump function of the heart becomes vibration and is included in the biological signal. In the sleep stage determination apparatus, this is extracted by the filter unit 3 to be recognized as a heartbeat signal. The heartbeat signal that has passed through the filter unit 3 is supplied to the automatic gain control unit 4. The sample period of the heartbeat signal is 4 milliseconds.

  The automatic gain control unit 4 is a so-called AGC circuit that automatically performs gain control so that the output of the filter unit 3 falls within a predetermined signal level range. The gain control by the automatic gain control unit 4 sets the gain so that the amplitude of the output signal becomes small when the peak value of the signal exceeds a predetermined upper limit threshold, and the peak value falls below the predetermined lower limit threshold. In such a case, the gain is set so that the amplitude increases. The automatic gain control unit 4 supplies the gain value (coefficient) when such gain control is performed to the signal strength calculation unit 5.

  The signal strength calculation unit 5 calculates the strength of the heartbeat signal based on the gain control coefficient applied to the heartbeat signal in the automatic gain control unit 4. The gain value obtained from the automatic gain control unit 4 described above is set to be small when the signal size is large and large when the signal size is small. Therefore, the gain value is inversely proportional to the gain value. Signal strength will be represented. The signal strength calculation unit 5 supplies the heart rate strength data to the normalization unit 6 in order to generalize the calculated heart rate strength data by eliminating individual differences and device differences.

  The normalization unit 6 normalizes the heart rate data calculated by the signal strength calculation unit 5 so that the amplitude falls within a predetermined measurement range. Specifically, the normalization unit 6 performs normalization by moving and averaging the heart rate intensity data detected by the signal intensity calculation unit 5. The normalizing unit 6 supplies the normalized normalized heart rate data to the variance value calculating unit 7. The processing performed by the normalization unit 6 will be described in detail later.

  The variance value calculation unit 7 calculates a variance value HID indicating the variation in data for a predetermined time for the normalized heart rate data normalized by the normalization unit 6. In this embodiment, when an index indicating a variation in data sampled within a certain time until a certain time point is referred to as a variance value, the standard deviation of the data is adopted as the variance value. Yes. Specifically, assuming that the signal strength data is measured every second, the variance value calculation unit 7 calculates, for example, the variance value of the data for 50 seconds from the series of signal strength data. In this case, the data for 50 seconds is calculated retroactively from a certain point of time, that is, the variance value of 50 heart rate intensity data is calculated, and then the data dispersion value for 50 seconds is calculated retroactively after the next one second. Repeat the process. As a result, the variance value calculation unit 7 can obtain time-series data at intervals of 1 second with respect to variations in signal intensity (variance values). The variance value calculation unit 7 supplies the time series data thus obtained to the sleep stage determination unit 8.

  The sleep stage determination unit 8 is based on the time series data of the dispersion value HID of the heart rate intensity. The six types of the sleep stage (shallow non-REM sleep stage) and the third non-REM sleep stage and the fourth non-REM sleep stage (deep non-REM sleep stage) are determined. The method for determining the sleep stage by the sleep stage determination unit 8 is not particularly limited. For example, the sleep stage determination unit 8 determines the sleep stage by applying the technique described in JP 2012-65853 A by the applicant. When there is a body motion, the signal shakes greatly and the variance value HID of the signal intensity also increases. Therefore, the sleep stage determination unit 8 performs an abnormal value process such as replacing the variance value HID of the signal intensity exceeding the predetermined value with the predetermined value in order to remove the influence of such an abnormal value. Then, the sleep stage determination unit 8 outputs the determined sleep stage information and displays it on a display device (not shown), prints it with a printing device, or stores it as data in a storage device.

  In such a sleep stage determination device, the biological signal detected by capturing the biological signal by the biological signal detecting unit 1 is amplified by the signal amplifying unit 2, and unnecessary signals are removed by the filter unit 3 by a bandpass filter or the like. Detect heart rate signal. In the sleep stage determination device, the strength of the heartbeat signal is calculated by the signal strength calculation unit 5 while performing gain control by the automatic gain control unit 4, and the normalization unit 6 normalizes the calculated strength of the heartbeat signal. The sleep stage determination unit 8 determines the sleep stage based on the dispersion value calculated by the dispersion value calculation unit 7 for the obtained normalized heart rate intensity data.

  Such a sleep stage determination apparatus performs the following normalization.

First, assuming that the gain value obtained from the automatic gain control unit 4 is AGCr and the heart rate intensity calculated by the signal intensity calculation unit 5 is Hin, Hin = AGCr is assumed to simplify the calculation. At this time, the normalization unit 6 assumes that the measurement range of the amplitude of the heartbeat signal is from 0 to 100, as the normalized heartbeat intensity HinN,
The moving average value of HinN = Hin * 100 / Hin is calculated. Here, the moving average value of the heart rate intensity Hin is, for example, 150 points, that is, a value obtained by performing a moving average on the data for 150 seconds, assuming that the signal intensity data is measured every second. is there.

Furthermore, when the reference value of the heart rate intensity is α (for example, 32), the normalization unit 6 corrects the normalized heart rate intensity HinN by multiplying the normalized heart rate intensity HinN by the following. The corrected final normalized heart rate intensity HinN is obtained.
Normalized heart rate HinN = β * HinN after correction
Where β = (γ * (Hin−α) + α) / α

  Note that γ can normally be γ = 1. The normalization unit 6 performs such a calculation to calculate the normalized heart rate intensity HinN, and normalizes the waveform of the heartbeat signal to a waveform that falls within 0 to 100% of the measurement range. As a result, the sleep stage determination device can eliminate individual differences in heart rate intensity as well as measurement device differences. In the sleep stage determination device, the dispersion value calculation unit 7 calculates a dispersion value HID for the normalized heart rate intensity HinN data thus obtained, and uses this for the sleep stage determination by the sleep stage determination unit 8. Become.

Here, γ may be γ = 1 as described above, but may be set according to the average value of the heart rate intensity Hin calculated over the entire measurement period by the signal intensity calculation unit 5 and the reference value α. . For example, if the reference value α is 22, γ is
γ = −0.1 * average value of heart rate intensity Hin calculated over the entire measurement period + 3.5
As a result, the inventors of the present invention have clarified that it is possible to obtain a very good agreement with the determination result of the sleep stage by the method using PSG. That is, in the sleep stage determination device, all the heartbeat signals during sleep are acquired, and after the measurement is completed, the process from the signal intensity calculation unit 5 to the sleep stage determination unit 8 including the process by the normalization unit 6 described above. In this case, γ is preferably set by a function of the average value of the heart rate intensity Hin calculated over the entire measurement period and the reference value α.

  Hereinafter, a time-series waveform obtained by performing processing including normalization on the actually measured heart rate signal is shown. Here, as shown in the following table 1, with respect to a heartbeat signal of the same person, an initial value of gain when performing automatic gain by the automatic gain control unit 4 and a peak value of heartbeat intensity serving as a reference for performing automatic gain control, Thus, it is verified whether or not the same sleep stage determination result can be obtained by constructing different environments for the measuring apparatuses A and B and normalizing the obtained signals. The measurement range of the heartbeat signal amplitude is 0 to 1000.

  FIG. 3 shows a time series waveform of the heart rate intensity Hin calculated by the signal intensity calculation unit 5, and FIG. 4 shows a time series waveform of the normalized heart rate intensity HinN normalized by the normalization unit 6 with respect to the waveform of FIG. FIG. 5 shows a time-series waveform of the dispersion value HID obtained by the dispersion value calculation unit 7 for the waveform of FIG. As can be seen from these figures, the sleep stage determination device can output a substantially equivalent waveform from each part while obtaining a normalized heart rate intensity HinN that falls within 0 to 100% of the measurement range even in different environments. it can.

  And when the sleep stage was calculated | required based on the time series waveform of the dispersion | distribution value HID shown in FIG.

  The sleep stage determination device can thus determine the sleep stage with high accuracy while performing normalization as needed.

  As described above, in the sleep stage determination device shown as an embodiment of the present invention, it is possible to perform universal measurement with no individual difference or device difference, because appropriate normalization is performed for heart rate intensity. As a result, the sleep stage can be determined with high accuracy.

  The present invention is not limited to the embodiment described above.

  For example, in the above-described embodiment, as a method for detecting a biological signal, a method for extracting a heartbeat signal from a biological signal obtained by the unconstrained biological signal detection unit 1 laid under the user's body is shown. However, the present invention is applicable to any detection means that can continuously obtain a heartbeat signal or a signal equivalent thereto. For example, the present invention can be applied as the biological signal detection unit 1 as long as it is a heart rate meter or pulse meter of the type worn on the body such as the wrist or the upper arm, and can record data continuously. is there.

  Further, as the biological signal detection unit 1, an air mat type detection unit as shown in FIG. 6 may be used instead of using the hollow tube described above. That is, the biological signal detection unit 30 shown in FIG. 6 is configured by connecting an air tube 30b to one end of an air mat 30a in which air is sealed, and further connecting a fine differential pressure sensor 30c to the air tube 30b. . In addition, the thing similar to what was demonstrated in the case of the biosignal detection part 1 using a hollow tube can be used for the micro differential pressure sensor 30c.

  Furthermore, in the above-described embodiment, the standard deviation is adopted as the variance value indicating the variation in heart rate intensity. However, the present invention may employ, for example, statistics such as variance, sum of deviation squares, and a predetermined range.

  Thus, it goes without saying that the present invention can be modified as appropriate without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1,30 Biosignal detection part 1a Pressure detection tube 1b, 30c Slight difference pressure sensor 2 Signal amplification part 3 Filter part 4 Automatic gain control part 5 Signal intensity calculation part 6 Normalization part 7 Variance calculation part 8 Sleep stage determination part 21 Sleeper 22 Hard sheet 23 Cushion sheet 30a Air mat 30b Air tube

Claims (4)

In a sleep stage determination device that determines a user's sleep stage based on a heartbeat signal detected non-invasively and unconstrained during sleep,
Heartbeat signal detecting means for detecting the user's heartbeat signal non-invasively and unconstrained;
The peak value is controlled to be constant by performing gain control on the heartbeat signal detected by the heartbeat signal detection means, and normalization is performed on the heartbeat signal intensity data calculated using the gain value at that time. Normalization means,
A sleep stage determination unit that determines the sleep stage of the user based on a variance value indicating a variation in data of a predetermined time calculated for the normalized heart rate data normalized by the normalization unit;
The normalizing means, when the gain value obtained by the gain control is AGCr and the intensity of the heartbeat signal is Hin,
A sleep stage determination device characterized by calculating a moving average value of HinN = Hin * 100 / Hin. The normalizing means, when the reference value of the intensity of the heartbeat signal is α,
Normalized heart rate HinN = β * HinN after correction
Where β = (γ * (Hin−α) + α) / α
The sleep stage determination device according to claim 1, wherein the corrected normalized heart rate HinN is calculated by calculating. The normalization unit performs normalization by setting the γ based on an average value of the intensity Hin of the heartbeat signal calculated over the entire measurement period and the reference value. Sleep stage determination device. In a sleep stage determination method for determining a user's sleep stage based on a heartbeat signal detected non-invasively and unconstrained during sleep,
A heartbeat signal detecting step of detecting the heartbeat signal of the user non-invasively and unconstrained by a predetermined heartbeat signal detecting means;
The processor that performs signal processing controls the peak value to be constant by performing gain control on the heartbeat signal detected in the heartbeat signal detection step, and the heartbeat signal calculated using the gain value at that time is controlled. A normalization step for normalizing the intensity data;
Sleep stage determination in which the processor determines the sleep stage of the user based on a variance value indicating a variation in data of a predetermined time calculated for the normalized heart rate data normalized in the normalization step A process,
In the normalization step, when the gain value obtained by the gain control is AGCr and the intensity of the heartbeat signal is Hin, the normalized heartbeat intensity HinN is
A sleep stage determination method characterized by calculating a moving average value of HinN = Hin * 100 / Hin.