Blood glucose level measurement device and blood glucose level measurement method

Abstract

This blood glucose level measurement device comprises: a light output unit; a light detection unit that detects light output by the light output unit and transmitted through a living body; a temporal phase difference calculation unit that calculates the temporal phase difference between an oxygenated hemoglobin waveform and a deoxygenated hemoglobin waveform on the basis of the detection result from the light detection unit; a blood glucose level calculation unit that calculates the blood glucose level of the living body on the basis of the temporal phase difference calculated by the temporal phase difference calculation unit; and a blood glucose level calibration unit that calibrates the blood glucose level calculated by the blood glucose level calculation unit. The blood glucose level calibration unit carries out the calibration such that the blood glucose level calculated by the blood glucose level calculation unit during sleep of the living body or during a prescribed period or time after waking up from the sleep corresponds to a preset reference blood glucose level.

Description

Blood glucose level measuring device and blood glucose level measuring method

[0001] The present disclosure relates to a blood glucose level measuring device and a blood glucose level measuring method.

[0002] A known technique for measuring blood glucose levels in a living body is, for example, the device described in Patent Document 1. The device described in Patent Document 1 calculates a temporal phase difference between an oxygenated hemoglobin waveform relating to the oxygenated hemoglobin concentration in the blood of the living body and a deoxygenated hemoglobin waveform relating to the deoxygenated hemoglobin concentration in the blood of the living body based on the detection result of light transmitted through the living body. The device then noninvasively calculates the blood glucose level of the living body based on the calculated temporal phase difference.

[0003] JP 2018-57511 A

[0004] In the blood glucose level measuring device described above, there is a risk that the calculated blood glucose level may deviate from the actual blood glucose level, resulting in a large error in the blood glucose level.

[0005] Therefore, an object of the present disclosure is to provide a blood glucose level measuring device and a blood glucose level measuring method that are capable of calculating blood glucose levels with high accuracy.

[0006] As a result of extensive research, the present inventors have found that, for example, when blood glucose levels of a standard living body such as a healthy individual are calculated non-invasively using light, the calculated blood glucose levels tend to be stable (i.e., fluctuate little) during sleep and immediately after waking up, which are resting states. The inventors have found that such blood glucose levels during sleep and immediately after waking up can be used to calibrate blood glucose levels calculated by a blood glucose measuring device and a blood glucose measuring method, and have completed the present disclosure.

[0007] That is, the blood glucose measuring device of the present disclosure is [1] "a blood glucose measuring device comprising: a light output unit that outputs light to a living organism; a light detection unit that detects the light output by the light output unit and transmitted through the living organism; a temporal phase difference calculation unit that calculates a temporal phase difference between an oxygenated hemoglobin waveform related to an oxygenated hemoglobin concentration in the blood of the living organism and a deoxygenated hemoglobin waveform related to a deoxygenated hemoglobin concentration in the blood of the living organism based on a detection result of the light detection unit; a blood glucose level calculation unit that calculates a blood glucose level of the living organism based on the temporal phase difference calculated by the temporal phase difference calculation unit; and a blood glucose level calibration unit that calibrates the blood glucose level calculated by the blood glucose level calculation unit, wherein the blood glucose level calibration unit performs the calibration so that the blood glucose level calculated by the blood glucose level calculation unit during a predetermined period while the living organism is sleeping or after waking up from the sleep corresponds to a preset reference blood glucose level."

[0008] In the blood glucose measuring device described in [1] above, the blood glucose level calculated non-invasively using light can be calibrated using stable blood glucose levels during sleep or for a predetermined period after waking up from sleep, thereby correcting the discrepancy between the calculated blood glucose level and the actual blood glucose level, and enabling accurate calculation of the blood glucose level.

[0009] The blood glucose measuring device of the present disclosure may be [2] "the blood glucose measuring device described in [1] above, wherein the blood glucose level calibration unit performs the calibration so that the blood glucose level calculated by the blood glucose level calculation unit during non-REM sleep of the living body corresponds to the reference blood glucose level." Since it has been found that blood glucose levels calculated during non-REM sleep tend to be more stable, the blood glucose measuring device described in [2] above makes it possible to perform calibration using a more stable blood glucose level.

[0010] The blood glucose measuring device of the present disclosure may be [3] "the blood glucose measuring device according to the above [1] or [2], wherein the blood glucose calibration unit performs the calibration so that the blood glucose level calculated by the blood glucose calculation unit becomes the reference blood glucose level when a certain time or more has passed since the living body fell asleep." Since it has been found that blood glucose levels calculated when a certain time or more has passed since the living body fell asleep tend to be more stable, the blood glucose measuring device described in the above [3] makes it possible to perform calibration using a more stable blood glucose level.

[0011] The blood glucose measuring device of the present disclosure may be [4] "the blood glucose measuring device according to any one of [1] to [3] above, wherein the blood glucose level calibration unit performs the calibration so that the blood glucose level that fluctuates within a predetermined range for a specified time or longer corresponds to the reference blood glucose level." The blood glucose measuring device described in [4] above makes it possible to perform calibration using a more stable blood glucose level.

[0012] The blood glucose measuring device of the present disclosure may be [5] "the blood glucose measuring device described in any of [1] to [4] above, wherein the blood glucose calibration unit determines the appropriateness of the calibration using the blood glucose level calculated by the blood glucose calculation unit during the sleep or for a predetermined period after waking up from the sleep, based on at least one of sleep information related to the sleep of the living body and dietary information related to eating and drinking before going to bed during the sleep, and if it determines that the calibration using the blood glucose level calculated by the blood glucose calculation unit during the sleep or for a predetermined period after waking up from the sleep is inappropriate, performs the calibration so that a typical value of the blood glucose level calculated by the blood glucose calculation unit within a certain period in the past corresponds to the reference blood glucose level."

[0013] Blood glucose levels calculated by a blood glucose level calculation unit during sleep or during a predetermined period after waking up from sleep may be unstable depending on the sleep conditions (e.g., sleep duration) and the eating and drinking conditions before bed (e.g., intake time). Therefore, the blood glucose measuring device described in [5] above determines the appropriateness of calibration using blood glucose levels calculated by a blood glucose level calculation unit during sleep or during a predetermined period after waking up from sleep (hereinafter also referred to as "sleep-based calibration") based on at least one of sleep information and dietary information. If the sleep-based calibration is determined to be inappropriate as a result of this determination, calibration is performed using a typical past blood glucose value instead of sleep-based calibration. This prevents calibration using unstable blood glucose levels.

[0014] The blood glucose level measurement method of the present disclosure is [6] "a blood glucose level measurement method comprising: a light output step of outputting light to a living organism; a light detection step of detecting the light output in the light output step and transmitted through the living organism; a temporal phase difference calculation step of calculating a temporal phase difference between an oxygenated hemoglobin waveform related to an oxygenated hemoglobin concentration in the blood of the living organism and a deoxygenated hemoglobin waveform related to a deoxygenated hemoglobin concentration in the blood of the living organism based on a detection result of the light detection step; a blood glucose level calculation step of calculating a blood glucose level of the living organism based on the temporal phase difference calculated in the temporal phase difference calculation step; and a blood glucose level calibration step of calibrating the blood glucose level calculated in the blood glucose level calculation step, wherein the calibration is performed in the blood glucose level calibration step so that the blood glucose level of the living organism calculated by the calculation unit during a predetermined period while the living organism is sleeping or after waking up corresponds to a preset reference blood glucose level." In the blood glucose measurement method described in [6] above, as in the blood glucose measurement device described above, it is possible to correct the discrepancy between the calculated blood glucose level and the actual blood glucose level, and to calculate the blood glucose level with high accuracy.

[0015] According to the present disclosure, it is possible to provide a blood glucose level measuring device and a blood glucose level measuring method that are capable of calculating blood glucose levels with high accuracy.

[0016] FIG. 1 is a conceptual diagram showing a blood glucose level measuring device according to an embodiment. FIG. 2 is a graph showing an example of the detection results of the light detection unit shown in FIG. 1 . FIG. 3 is a block diagram showing the functional configuration of the ECU shown in FIG. 1 . FIG. 4 is a graph showing an oxygenated hemoglobin waveform and a deoxygenated hemoglobin waveform calculated from the detection results shown in FIG. 2 . FIG. 5 is a schematic diagram showing the oxygenated hemoglobin waveform and the deoxygenated hemoglobin waveform shown in FIG. 4 . FIG. 6( a) is a graph illustrating a first example of a process for correlating a blood glucose level calculated by the blood glucose level calculation unit shown in FIG. 3 with a reference blood glucose level. FIG. 6( b) is another graph illustrating a first example of a process for correlating a blood glucose level calculated by the blood glucose level calculation unit shown in FIG. 3 with a reference blood glucose level. FIG. 7( a) is a graph illustrating a second example of a process for correlating a blood glucose level calculated by the blood glucose level calculation unit shown in FIG. 3 with a reference blood glucose level. FIG. 7( b) is another graph illustrating a second example of a process for correlating a blood glucose level calculated by the blood glucose level calculation unit shown in FIG. 3 with a reference blood glucose level. FIG. 8(a) is a graph illustrating a third example of a process for correlating a blood glucose value calculated by the blood glucose level calculation unit of FIG. 3 with a reference blood glucose level. FIG. 8(b) is another graph illustrating a third example of a process for correlating a blood glucose value calculated by the blood glucose level calculation unit of FIG. 3 with a reference blood glucose level. FIG. 9(a) is a graph illustrating a fourth example of a process for correlating a blood glucose value calculated by the blood glucose level calculation unit of FIG. 3 with a reference blood glucose level. FIG. 9(b) is another graph illustrating a fourth example of a process for correlating a blood glucose value calculated by the blood glucose level calculation unit of FIG. 3 with a reference blood glucose level. FIG. 10(a) is a flowchart illustrating a blood glucose measurement method according to an embodiment. FIG. 10(b) is another flowchart illustrating a blood glucose measurement method according to an embodiment. FIG. 11 is a graph illustrating an example of a time course of a blood glucose level of a healthy subject measured by the blood glucose measurement device of FIG. 1.

[0017] Hereinafter, the embodiments will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and redundant explanations will be omitted.

[0018] The blood glucose level measuring device 1 shown in Fig. 1 is, for example, a wearable device, a smartphone, or a pulse oximeter. Examples of wearable devices include a smart watch and a smart ring. The blood glucose level measuring device 1 of this embodiment is a smart watch that can be worn at all times by a living body 6 and has a function of measuring the blood glucose level of the living body 6 (the user). The living body 6 has a superficial tissue 61 and an internal tissue 62 that is located more internally than the superficial tissue 61. The surface 61a of the superficial tissue 61 is the surface of the skin of the living body 6. The living body 6 is, for example, a human body.

[0019] The blood glucose measuring device 1 measures the blood glucose level of a living organism 6. The blood glucose measuring device 1 includes a main body 2, a light output unit 3, a light detection unit 4, an inertial sensor 10, and an ECU (Electronic Control Unit) 50. The main body 2 has a front face 2a and a back face 2b facing the opposite side to the front face 2a. A display that displays various information about the blood glucose measuring device 1 is provided on the front face 2a side of the main body 2. The display here is a touch panel display that allows various settings and input / output of information, and constitutes an input / output device. The blood glucose measuring device 1 is worn on the living organism 6 so that the back face 2b comes into contact with the skin of the living organism 6.

[0020] The light output unit 3 is provided in the main body 2. The light output surface of the light output unit 3 is exposed from the back surface 2b of the main body 2. The light output unit 3 has a light source that outputs measurement light (light) L to the living body 6. The light source is, for example, a light-emitting diode (LED), a laser diode (LD), or a superluminescent diode (SLD). The measurement light L is emitted from the back surface 2b. The measurement light L emitted from the light output unit 3 propagates inside the living body 6 and is then emitted again from the living body 6. The light output unit 3 is controlled by the ECU 50.

[0021] The wavelength range of the measurement light L is, for example, from the red wavelength region of visible light to the near-infrared region (670 nm to 2500 nm). That is, the light output unit 3 outputs measurement light L within the range from the red wavelength region of visible light to the near-infrared region. The light output unit 3 outputs measurement light L, for example, with wavelengths different from each other. In this case, the light output unit 3 has multiple (for example, three) light sources. The first light source outputs measurement light L having a wavelength of, for example, 735 nm, the second light source outputs measurement light L having a wavelength of, for example, 810 nm, and the third light source outputs measurement light L having a wavelength of, for example, 850 nm. Note that the light output unit 3 may have a single light source that outputs probe light (for example, white light) containing mutually different wavelength components.

[0022] The light detection unit 4 is provided in the main body 2. The light detection unit 4 is separated from the light output unit 3. The light detection surface of the light detection unit 4 is exposed from the rear surface 2b of the main body 2. The light detection unit 4 has a light detection element that detects measurement light (transmitted light) L output from the light output unit 3 and transmitted through the living body 6. The light detection element is, for example, a photodiode (PD). The light detection unit 4 also has a preamplifier that amplifies the photocurrent output from the light detection element and an A / D conversion circuit that converts the signal amplified by the preamplifier into a digital signal. The light detection unit 4 may also have a CCD image sensor or a CMOS image sensor. The light detection unit 4 transmits a signal related to the intensity of the measurement light L to the ECU 50.

[0023] 2 , the light detection unit 4 detects at least first data D1 and second data D2. The first data D1 is, for example, a change over time in the intensity of transmitted light when measurement light L having a first wavelength passes through the living body 6 and enters the light detection unit 4, and the second data D2 is, for example, a change over time in the intensity of transmitted light when measurement light L having a second wavelength passes through the living body 6 and enters the light detection unit 4. Each of the first data D1 and the second data D2 periodically fluctuates over time. Note that the respective periods of the first data D1 and the second data D2 approximately coincide with the cardiac cycle of the living body 6.

[0024] The inertial sensor 10 is provided in the main body 2. The inertial sensor 10 constitutes a body motion detection unit that detects parameters related to the body motion of the living body 6 (hereinafter simply referred to as "body motion parameters"). The inertial sensor 10 includes a triaxial acceleration sensor that detects acceleration in each of three mutually orthogonal axial directions (e.g., X, Y, and Z directions). In this case, it is possible to detect translational motion of the living body 6 in each of the three axial directions. Instead of or in addition to the triaxial acceleration sensor, the inertial sensor 10 may include a triaxial gyro sensor that detects angular acceleration around three mutually orthogonal axes. In this case, it is possible to detect rotational motion of the living body 6 around the three axes. The inertial sensor 10 may further include a geomagnetic sensor that detects the direction of the geomagnetic field. In this case, it is possible to detect the direction in which the blood glucose level measuring device 1 is facing in an absolute coordinate system. By combining the detection results of the triaxial acceleration sensor, the triaxial gyro sensor, and the geomagnetic sensor, it is possible to recognize the orientation of the blood glucose level measuring device 1 and the direction of motion of the living body 6 based on absolute coordinates. The inertial sensor 10 transmits signals relating to the body movement parameters to the ECU 50 .

[0025] The ECU 50 is provided in the main body 2. The ECU 50 is an electronic control unit including a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The ECU 50 executes various processes, for example, by having the CPU execute programs stored in the ROM or RAM. The ECU 50 calculates the pulse rate of the living body 6 based on the detection results of the light detection unit 4. The method for calculating the pulse rate is not particularly limited, and various known methods may be used. The ECU 50 calculates the blood glucose level of the living body 6 based on the detection results of the light detection unit 4 (details will be described later). The ECU 50 may be composed of a single electronic unit or multiple electronic units capable of communicating with each other. The pulse rate may be detected by a heart rate sensor.

[0026] As shown in Fig. 3, the ECU 50 has, as its functional components, a time phase difference calculation unit 51, a blood glucose level calculation unit 52, a storage unit 53, and a blood glucose level calibration unit 54. As shown in Fig. 4, the time phase difference calculation unit 51 calculates an oxygenated hemoglobin waveform P1 and a deoxygenated hemoglobin waveform P2 based on the detection result of the light detection unit 4. The oxygenated hemoglobin waveform P1 is a waveform of oxygenated hemoglobin (O ２ The first data D1 and the second data D2 are data relating to the concentration of deoxygenated hemoglobin (HHb), and the deoxygenated hemoglobin waveform P2 is data relating to the concentration of deoxygenated hemoglobin (HHb) in the blood of the living body 6. The temporal phase difference calculation unit 51 calculates the oxygenated hemoglobin waveform P1 and the deoxygenated hemoglobin waveform P2 by performing spectroscopic calculation processing based on, for example, the Modified Beer-Lambert (MBL) method on the first data D1 and the second data D2.

[0027] Specifically, the temporal phase difference calculation unit 51 calculates the difference between the intensity of the first data D1 at the first time and the intensity of the first data D1 at the second time (the amount of change over time in the intensity of the first data D1), the difference between the intensity of the second data D2 at the first time and the intensity of the second data D2 at the second time (the amount of change over time in the intensity of the second data D2), the absorption coefficients of oxygenated hemoglobin and deoxygenated hemoglobin for the first data D1, and the O absorption coefficient for the second data D2. ２ Based on the respective absorption coefficients of Hb and HHb, the relative change in oxygenated hemoglobin over time (ΔO ２ The temporal phase difference calculation unit 51 calculates the temporal relative change in ΔO ２ Hb and ΔHHb are continuously calculated at predetermined time intervals (for example, about 16 milliseconds). ２ The change in Hb over time is the oxygenated hemoglobin waveform P1 shown in Fig. 4, and the change in ΔHHb over time is the deoxygenated hemoglobin waveform P2 shown in Fig. 4. The concentration index on the vertical axis in Fig. 4 is, for example, a volume concentration index (concentration x optical path length).

[0028] The temporal phase difference calculation unit 51 calculates the temporal phase difference (hereinafter simply referred to as "temporal phase difference") between the oxygenated hemoglobin waveform P1 and the deoxygenated hemoglobin waveform P2. FIG. 5 is a schematic diagram of the oxygenated hemoglobin waveform P1 and the deoxygenated hemoglobin waveform P2 shown in FIG. 4. The temporal phase difference calculation unit 51 calculates the time difference between a first characteristic point C1 of the oxygenated hemoglobin waveform P1 and a second characteristic point C2 of the deoxygenated hemoglobin waveform P2 as the temporal phase difference Δθ. In this embodiment, the first characteristic point C1 is a bottom point of the oxygenated hemoglobin waveform P1, and the second characteristic point C2 is a bottom point of the deoxygenated hemoglobin waveform P2. The first characteristic point C1 may be, for example, a peak point or a notch point of the oxygenated hemoglobin waveform P1, and the second characteristic point C2 may be, for example, a peak point or a notch point of the deoxygenated hemoglobin waveform P2. In this embodiment, the method for calculating the temporal phase difference Δθ may be, for example, the method disclosed in Japanese Patent No. 6846152. The method for calculating the temporal phase difference Δθ is not particularly limited, and various known methods may be used.

[0029] The blood glucose level calculation unit 52 calculates the blood glucose level of the living body 6 based on the temporal phase difference Δθ calculated by the temporal phase difference calculation unit 51. For example, the blood glucose level calculation unit 52 calculates the blood glucose level of the living body 6 using the formula G = α × Δθ - β, where G is the blood glucose level of the living body 6, Δθ is the temporal phase difference, and α and β are coefficients determined according to the glucose metabolic capacity of the living body 6 and the measurement site. In this embodiment, the blood glucose level may be calculated using, for example, the methods disclosed in Japanese Patent No. 6846152. The blood glucose level calculation method is not particularly limited, and various known methods may be used.

[0030] The memory unit 53 stores and accumulates the blood glucose levels of the living body 6 calculated by the blood glucose level calculator 52 in chronological order, correlating them with time. The memory unit 53 stores and accumulates the body movement parameters detected by the inertial sensor 10 in chronological order, correlating them with time. The memory unit 53 stores biometric information. For example, if the living body 6 is a human body, the biometric information includes at least one of the sex, build, height, weight, race, and age. The biometric information may be acquired based on an input via the touch panel display of the main body 2, or may be acquired from an external device via communication.

[0031] The storage unit 53 stores sleep information related to the sleep of the living body 6 and dietary information related to the food and drink consumed before going to bed during that sleep. The sleep information is information that can determine whether the living body 6 is sleep-deprived. The sleep information includes, for example, the sleep duration of the most recent sleep (e.g., the previous day), the duration of the most recent deep sleep (non-REM sleep), and the time of fall asleep during the most recent sleep. The sleep information is not particularly limited and may include other sleep-related information. The sleep information may be acquired by a known method based on the pulse and body movement parameters of the living body 6 stored in the storage unit 53. Alternatively, the sleep information may be acquired by user input via a touch panel display of the main body 2, or from an external device via communication.

[0032] The food and drink information is information that can determine whether the living body 6 ate and drank too much before the most recent sleep. The food and drink information includes, for example, the time of the most recent meal, the blood glucose level before the most recent sleep, and the total calorie content of the most recent meal and drink. The food and drink information is not particularly limited and may include other information related to food and drink. The food and drink information may be obtained, for example, by user input via the touch panel display of the main body 2 (arbitrary input or selection from a food item list), or may be obtained from an external source via communication. Alternatively, the food and drink information may be estimated, for example, by image analysis of a photo taken with a camera or the like of the smart device.

[0033] The blood glucose level calibration unit 54 calibrates the blood glucose level calculated by the blood glucose level calculation unit 52. Specifically, the blood glucose level calibration unit 54 performs calibration (hereinafter also referred to as "sleep-based calibration") so that the blood glucose level calculated by the blood glucose level calculation unit 52 while the living body 6 is sleeping or for a predetermined period after waking up from the sleep corresponds to a preset reference blood glucose level. The blood glucose level calibration unit 54 periodically performs sleep-based calibration. There are no particular limitations on the frequency with which the blood glucose level calibration unit 54 performs sleep-based calibration, and for example, the sleep-based calibration may be performed at a set time every day.

[0034] In the calibration using sleep in this embodiment, calibration is performed so that the blood glucose level calculated by the blood glucose level calculation unit 52 during the most recent sleep of the living body 6 corresponds to the reference blood glucose level. Specifically, in the calibration using sleep, the blood glucose level calibration unit 54 performs calibration so that the blood glucose level calculated by the blood glucose level calculation unit 52 during non-REM sleep of the living body 6 when a certain time or more has passed since the most recent falling asleep of the living body 6 and whose fluctuations have been within a predetermined range for a specified time or more corresponds to the reference blood glucose level.

[0035] Whether the living body 6 is asleep, whether it is in non-REM sleep, and whether a certain amount of time has passed since falling asleep can be determined by a known method based on the pulse and body movement parameters of the living body 6 stored in the storage unit 53. The predetermined period, the fixed time, and the specified time are not particularly limited and can be set in advance. The predetermined period, the fixed time, and the specified time may be fixed values ​​or may be variable values ​​that can be changed by, for example, user input. The fixed time may be, for example, 30 minutes or 3 hours.

[0036] The reference blood glucose level may be a median value statistically calculated from biological information such as the age, sex, and weight of the living body 6. The reference blood glucose level may be a self-measured blood glucose value using blood collected from the living body 6. The reference blood glucose level may be a single value, multiple values, or a continuous value over time (time series data). The reference blood glucose level may be a value measured by collecting venous blood. The reference blood glucose level may be a fasting blood glucose level from the most recent health check. When blood glucose levels are managed based on relative fluctuations from the time of waking up rather than absolute values, the reference blood glucose level may be 0 (baseline). The reference blood glucose level is stored in the memory unit 53. The reference blood glucose level may be obtained, for example, by user input via the touch panel display of the main body unit 2, or may be obtained from an external device via communication.

[0037] Here, examples of the process of correlating the blood glucose level calculated by the blood glucose level calculation unit 52 with the reference blood glucose level in the calibration using sleep in this embodiment will be described with reference to the graphs in Figures 6(a) to 9(b). In the calibration using sleep, the blood glucose level calculated by the blood glucose level calculation unit 52 is calibrated to the reference blood glucose level by performing at least one of addition or subtraction (parallel movement in the vertical direction on the graph) and multiplication or division (expansion or contraction in the vertical direction on the graph). The graphs in each figure show the change over time in the blood glucose level calculated by the blood glucose level calculation unit 52, with the vertical axis corresponding to the blood glucose level and the horizontal axis corresponding to the time.

[0038] 6(a) and 6(b), the "blood glucose level G1 at a specific point" calculated by the blood glucose level calculation unit 52 during a predetermined period while the living body 6 is sleeping or after waking up from the sleep is adjusted to be equal to the reference blood glucose level K1. Specifically, a coefficient (for example, the above-mentioned coefficient β) used to calculate the blood glucose level in the blood glucose level calculation unit 52 is adjusted so that the blood glucose level G1 becomes equal to the reference blood glucose level K1, and the blood glucose level waveform is shifted up and down in parallel on the graph.

[0039] 7(a) and 7(b), the "blood glucose level G2 in a specific time domain TL" calculated by the blood glucose level calculation unit 52 during a predetermined period while the living body 6 is sleeping or after waking up from the sleep is adjusted to be equal to the reference blood glucose level K2, which is a continuous value in the time domain TL, using the so-called least squares method. Specifically, a coefficient (e.g., the above-mentioned coefficient α) used in calculating the blood glucose level in the blood glucose level calculation unit 52 is adjusted so that the sum of squares of the distances between the blood glucose level G2 in the time domain TL and the reference blood glucose level K2 in the time domain TL is minimized, and the blood glucose level waveform is stretched or contracted in the vertical direction on the graph.

[0040] 8(a) and 8(b), "blood glucose levels G31, G32 at two specific points" calculated by the blood glucose level calculation unit 52 during a predetermined period while the living body 6 is sleeping or after waking up from the sleep are adjusted to be equal to the reference blood glucose levels K31, K32, respectively. Specifically, a coefficient (for example, the above-mentioned coefficient β) used to calculate the blood glucose level in the blood glucose level calculation unit 52 is adjusted so that the blood glucose levels G31, G32 are equal to the reference blood glucose levels K31, K32, respectively, and the blood glucose level waveform is stretched or contracted in the vertical direction on the graph.

[0041] 9(a) and 9(b), "blood glucose levels G41, G42 at two specific points" calculated by the blood glucose level calculation unit 52 during a predetermined period while the living body 6 is sleeping or after waking up from the sleep are adjusted to be equal to the reference blood glucose levels K41, K42, respectively. Specifically, the coefficients (e.g., the above-mentioned coefficients α and β) used to calculate the blood glucose levels in the blood glucose level calculation unit 52 are adjusted, and the blood glucose level waveform is translated and expanded or contracted in the vertical direction on the graph, so that the blood glucose levels G41, G42 become equal to the reference blood glucose levels K41, K42, respectively.

[0042] 3 , the blood glucose calibration unit 54 determines whether sleep-based calibration is appropriate based on at least one of the sleep information and the eating and drinking information stored in the memory unit 53. For example, the blood glucose calibration unit 54 determines that the living body 6 is sleep-deprived and that sleep-based calibration is inappropriate when any of the following conditions occur: the sleep duration of the most recent sleep is shorter than a first predetermined time, the duration of the most recent non-REM sleep is shorter than a second predetermined time (the second predetermined time < the first predetermined time), or the sleep onset time of the most recent sleep is later than a typical past sleep onset time by a predetermined time or more. Furthermore, for example, the blood glucose calibration unit 54 determines that the living body 6 has eaten too much and that sleep-based calibration is inappropriate when any of the following conditions occur: the time of the most recent meal or drink was later than a predetermined time, the blood glucose level before the most recent sleep was higher than a predetermined blood glucose level, or the total calorie content of the most recent meal or drink was higher than a predetermined calorie content.

[0043] If the blood glucose level calibration unit 54 determines that sleep-based calibration is inappropriate, it performs calibration (hereinafter also referred to as "typical value calibration") so that a typical blood glucose value previously calculated by the blood glucose level calculation unit 52 corresponds to a reference blood glucose level. The typical blood glucose value may be the average blood glucose value calculated by the blood glucose level calculation unit 52 within a certain period in the past (for example, within the most recent specified number of days) and stored in the storage unit 53. The typical value is not particularly limited, and may be, for example, the median, mode, or representative value of blood glucose values ​​within the certain period in the past.

[0044] Next, the blood glucose level measurement method of this embodiment will be described. As shown in Fig. 10(a), in the blood glucose level measurement method of this embodiment, first, the light output unit 3 outputs measurement light L to the living body 6 (step S1). Step S1 corresponds to the light output step. Next, the measurement light L transmitted through the living body 6 is detected by the light detection unit 4 (step S2). Step S2 corresponds to the light detection step.

[0045] Next, the temporal phase difference calculation unit 51 calculates the temporal phase difference Δθ between the oxygenated hemoglobin waveform P1 and the deoxygenated hemoglobin waveform P2 based on the detection result of the measurement light L transmitted through the living body 6 (step S3). Step S3 corresponds to the temporal phase difference calculation step. The blood glucose level calculation unit 52 calculates the blood glucose level of the living body 6 based on the temporal phase difference Δθ calculated in step S3, and the blood glucose level is associated with time and stored in the memory unit 53 (step S4). Step S4 corresponds to the blood glucose level calculation step.

[0046] Furthermore, in the blood glucose measurement method of this embodiment, a blood glucose calibration step is periodically performed to calibrate the blood glucose level calculated in step S4. In the blood glucose calibration step, first, the blood glucose calibration unit 54 acquires sleep information and dietary information from the storage unit 53 (step S11). The blood glucose calibration unit 54 determines whether sleep-based calibration is appropriate based on the sleep information and dietary information (step S12). If step S12 is YES, i.e., if sleep-based calibration is appropriate, the blood glucose calibration unit 54 performs sleep-based calibration (step S13). On the other hand, if step S12 is NO, i.e., if sleep-based calibration is inappropriate, the blood glucose calibration unit 54 performs typical value calibration (step S14).

[0047] FIG. 11 is a graph showing an example of the progression of blood glucose levels of a healthy individual measured using the blood glucose measuring device 1. In the graph, the vertical axis represents blood glucose level, and the horizontal axis represents time. The example in the graph shows a case in which the individual woke up at 7:00 a.m. and had breakfast at 8:00 a.m. When the blood glucose level of a typical living body 6 of a healthy individual or the like is calculated noninvasively using the blood glucose measuring device 1 and the measurement light L, as shown in FIG. 11 , it has been found that the calculated blood glucose level tends to be stable during sleep, which is a resting state, and immediately after waking up. In this regard, the blood glucose measuring device 1 and blood glucose measuring method according to this embodiment can calibrate the calculated blood glucose level using stable blood glucose levels during sleep or for a predetermined period after waking up from sleep. This makes it possible to correct the discrepancy between the calculated blood glucose level and the actual blood glucose level, thereby enabling accurate calculation of the blood glucose level.

[0048] In the blood glucose measuring device 1, the blood glucose level calibration unit 54 performs sleep-based calibration so that the blood glucose level calculated by the blood glucose level calculation unit 52 during non-REM sleep of the living body 6 corresponds to the reference blood glucose level. In this case, it has been found that the blood glucose level calculated by the blood glucose measuring device 1 during non-REM sleep tends to be more stable, and therefore it is possible to perform sleep-based calibration using a more stable blood glucose level.

[0049] In the blood glucose measuring device 1, the blood glucose level calibration unit 54 performs calibration using sleep so that the blood glucose level calculated by the blood glucose level calculation unit 52 becomes the reference blood glucose level when a certain amount of time has passed since the living body 6 fell asleep. In this case, it has been found that the blood glucose level calculated when a certain amount of time has passed since the living body 6 fell asleep tends to be more stable, and therefore it is possible to perform calibration using a more stable blood glucose level.

[0050] In the blood glucose measuring device 1, the blood glucose calibration unit 54 performs calibration using sleep so that a blood glucose level whose fluctuations are within a predetermined range for a specified time or longer corresponds to a reference blood glucose level. In this case, it is possible to perform calibration using sleep using a more stable blood glucose level.

[0051] The blood glucose level calculated by the blood glucose level calculation unit 52 during sleep or for a predetermined period after waking up from sleep may be unsettling depending on the sleep conditions (such as sleep duration) and the eating and drinking conditions before going to bed (such as intake time). Therefore, in the blood glucose measuring device 1, the blood glucose level calibration unit 54 determines whether sleep-based calibration is appropriate based on at least one of the sleep information and the eating and drinking information, and if it determines that sleep-based calibration is inappropriate, performs typical value calibration so that typical blood glucose values ​​calculated by the blood glucose level calculation unit 52 within a certain period in the past correspond to the reference blood glucose level. This makes it possible to prevent sleep-based calibration from being performed using unstable blood glucose levels.

[0052] In principle, the blood glucose measuring device 1 of this embodiment is a wearable device that can be worn at all times by the living body 6, which is why the blood glucose level calculation unit 52 can calculate the blood glucose level during sleep and for a predetermined period after waking up from the sleep. Therefore, the above-mentioned effects of the sleep-based calibration can be said to be effects that are unique to wearable devices.

[0053] As described above, one aspect of the present disclosure is not limited to the above embodiment.

[0054] In the above embodiment, the blood glucose level calibration unit 54 may perform calibration so that the calculated blood glucose level corresponds to the reference blood glucose level when at least a certain time has passed since the living body 6 most recently fell asleep, when the living body 6 is in non-REM sleep, or when blood glucose level fluctuations are within a predetermined range for at least a specified time. Note that if there are multiple time regions during sleep where blood glucose level fluctuations are within a predetermined range for at least a specified time, it is desirable to perform sleep-utilization calibration using the blood glucose level in the latest time region (closest to wake-up) among them.

[0055] In the above embodiment, the body movement parameters are acquired by the inertial sensor 10 provided in the main body 2. However, instead of or in addition to this, the inertial sensor 10 may be mounted on an external host device, and the ECU 50 may acquire the body movement parameters through communication with the host device. In the above embodiment, the sleep time period targeted for sleep utilization calibration may be either day or night, and may be, for example, nighttime sleep or daytime sleep.

[0056] In the above embodiment, the ECU 50 is provided in the main body 2, but the ECU 50 does not have to be provided in the main body 2 and may be provided in, for example, a server that can communicate with the main body 2. In the above embodiment, the light output unit 3 may include a broadband light source. For example, a white LED is used as the broadband light source. In this case where the light output unit 3 includes a broadband light source, the light detection unit 4 may include a spectroscope.

[0057] The components in the above-described embodiment and modified examples are not limited to the materials and shapes described above, and various materials and shapes can be applied. Furthermore, the components in the above-described embodiment and modified examples can be arbitrarily applied to the components in other embodiments or modified examples.

[0058] 1...blood glucose level measuring device, 3...light output unit, 4...light detection unit, 6...living body, 51...temporal phase difference calculation unit, 52...blood glucose level calculation unit, 54...blood glucose level calibration unit, K1, K2, K31, K32, K41, K42...reference blood glucose levels, L...measurement light (light).

Claims

1. A blood glucose measuring device comprising: a light output unit that outputs light to a living organism; a light detection unit that detects the light output by the light output unit and transmitted through the living organism; a temporal phase difference calculation unit that calculates a temporal phase difference between an oxygenated hemoglobin waveform related to the oxygenated hemoglobin concentration in the blood of the living organism and a deoxygenated hemoglobin waveform related to the deoxygenated hemoglobin concentration in the blood of the living organism based on the detection result of the light detection unit; a blood glucose level calculation unit that calculates a blood glucose level of the living organism based on the temporal phase difference calculated by the temporal phase difference calculation unit; and a blood glucose level calibration unit that calibrates the blood glucose level calculated by the blood glucose level calculation unit, wherein the blood glucose level calibration unit performs the calibration so that the blood glucose level calculated by the blood glucose level calculation unit during the sleeping period of the living organism or for a predetermined period after waking up from the sleeping period corresponds to a predetermined reference blood glucose level.

2. The blood glucose level measuring device of claim 1, wherein the blood glucose level calibration unit performs the calibration so that the blood glucose level calculated by the blood glucose level calculation unit during non-REM sleep of the living body corresponds to the reference blood glucose level.

3. A blood glucose measuring device as described in claim 1 or 2, wherein the blood glucose calibration unit performs the calibration so that the blood glucose level calculated by the blood glucose calculation unit becomes the reference blood glucose level when a certain amount of time has passed since the living body fell asleep.

4. A blood glucose measuring device according to claim 1 or 2, wherein the blood glucose calibration unit performs the calibration so that the blood glucose level whose fluctuations are within a predetermined range for a specified period of time or more corresponds to the reference blood glucose level.

5. The blood glucose level calibration unit determines the appropriateness of the calibration using the blood glucose level calculated by the blood glucose level calculation unit during the sleep or a predetermined period after waking up from the sleep based on at least one of sleep information regarding the sleep of the living body and food and drink information regarding food and drink before going to bed, and if it determines that the calibration using the blood glucose level calculated by the blood glucose level calculation unit during the sleep or a predetermined period after waking up from the sleep is inappropriate, performs the calibration so that the typical blood glucose value calculated by the blood glucose level calculation unit within a certain period in the past corresponds to the reference blood glucose level. A blood glucose level measuring device as described in claim 1 or 2.

6. A blood glucose measurement method comprising: a light output step of outputting light to a living organism; a light detection step of detecting the light output in the light output step and transmitted through the living organism; a temporal phase difference calculation step of calculating a temporal phase difference between an oxygenated hemoglobin waveform relating to the oxygenated hemoglobin concentration in the blood of the living organism and a deoxygenated hemoglobin waveform relating to the deoxygenated hemoglobin concentration in the blood of the living organism based on the detection result of the light detection step; a blood glucose level calculation step of calculating a blood glucose level of the living organism based on the temporal phase difference calculated in the temporal phase difference calculation step; and a blood glucose level calibration step of calibrating the blood glucose level calculated in the blood glucose level calculation step, wherein the calibration is performed in the blood glucose level calibration step so that the blood glucose level of the living organism calculated in the blood glucose level calculation step during a predetermined period while the living organism is sleeping or after waking up corresponds to a predetermined reference blood glucose level.

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