Circadian rhythm measurement system

Abstract

This circadian rhythm measurement system comprises: a core body temperature conversion unit (21) that calculates, for each first cycle, the core body temperature of a user from the skin temperature of the user as measured by a sensor device (1), said first cycle being the the same as the measurement cycle of the sensor device (1); a circadian rhythm conversion unit (23) that calculates, as a lowest point time, the most recent time at which the core body temperature was a local minimum value, on the basis of the core body temperature in a fixed period from the past until most recently; and an output unit (25) that notifies the user of the time that results from adding a prescribed time period to the lowest point time, as a time at which light stimulation should be performed. The circadian rhythm conversion unit (23) calculates the lowest point time for each second cycle, which is equal to or longer than the first cycle and shorter than the prescribed time period.

Description

Circadian rhythm measurement system

[0001] The present invention relates to a circadian rhythm measurement system that provides a user with timing information for a light stimulus that is to be performed for the purpose of correcting the circadian rhythm.

[0002] Recent research has shown that the biological cycle (circadian rhythm) controlled by the body's endogenous clock mechanism is closely related to various aspects of life, such as the quality of sleep, exercise, and work, as well as the effectiveness of medication (pharmacology) and the effects of diet (nutrition). Circadian rhythms are maintained on a roughly 24-hour cycle, but irregular lifestyle habits and shift work, including night shifts, can cause them to fall behind their normal rhythm.

[0003] It is known that a delay in circadian rhythm can be corrected by light stimulation (Non-Patent Document 1). When light stimulation is administered to a person with a delayed circadian rhythm 2 to 4 hours after the nadir of their core body temperature, a significant advancement effect in correcting the circadian rhythm can be achieved. However, if the time of administration is off, the corrective effect is lost. Therefore, it is necessary to realize a system that can measure a person's circadian rhythm.

[0004] The configuration of a conventional system is shown in Fig. 6. The temperature sensor 101 of the sensor device 100 detects the body temperature T Ｒａｗ (for example, skin temperature). Ｒａｗ The data is transmitted to the processing terminal 200.

[0005] The data receiving unit 201 of the processing terminal 200 receives the temperature T Ｒａｗ The core body temperature conversion unit 202 receives the temperature T Ｒａｗ The user's core body temperature T ＣＢＴ The circadian rhythm conversion unit 203 converts the deep body temperature T ＣＢＴ The lowest point time t Ｔｍｉｎ The output unit 204 calculates the lowest point time t Ｔｍｉｎ For example, at time t three hours later ｌｉｇｈｔ The user is notified of this time as the time when light stimulation should be performed.

[0006] Conventionally, deep body temperature T ＣＢＴ The lowest point time t ＴｍｉｎAs a method for calculating the nadir time t, a method of performing a cosinor analysis on the measured data after the fact has been proposed (Non-Patent Document 2). The problem with the conventional system will be explained using Fig. 7. In the example of Fig. 7, the processing terminal 200 receives data from the sensor device 100 and calculates the nadir time t Ｔｍｉｎ The analysis timings at which the above calculations are performed are designated as t10 and t11. ＣＢＴ _ ｋｆ is the estimated value of the deep body temperature calculated by the deep body temperature conversion unit 202, T ＣＢＴ _ ｆｉｔ The circadian rhythm conversion unit 203 calculates the estimated value T of the deep body temperature by the cosinor method. ＣＢＴ _ ｋｆ In the example of FIG. 7, the periods of data transmitted from the sensor device 100 are designated as D10 and D11. However, during the period D11, the temperature T Ｒａｗ There is a missing period D12 with no data. The dotted line LT indicates the time obtained by adding three hours to the lowest point of the vertical axis on the right side.

[0007] In the conventional system, the lowest point is at time t Ｔｍｉｎ However, in order to correct the circadian rhythm, the nadir time t Ｔｍｉｎ Even if light stimulation is performed three hours after the lowest point t Ｔｍｉｎ The timing three hours later (the timing indicated by the dotted line LT) is earlier than time t10. Therefore, it is not possible to perform the light stimulation at an appropriate time. Ｔｍｉｎ When the temperature T Ｒａｗ Since there is a missing period D12 in the data of Ｔｍｉｎ t in Figure 7 Ｔｍｉｎ ' indicates the true lowest point time that should be calculated.

[0008] As described above, conventional systems have the problem that the timing of the desired light stimulation may be missed, and there is also the problem that if there is a missing period in the data, the time of the nadir may be calculated inaccurately.

[0009] DSMinors, et al., “A human phase-response curve to light”, Neuroscience Letters, Volume 133, Issue 1, pp. 36-40, 1991 G. Cornelissen, “Cosinor-based rhythmometry”, Theoretical Biology and Medical Modelling, Volume 11, Article number 16, 2014

[0010] The present invention has been made to solve the above-mentioned problems, and aims to provide a circadian rhythm measurement system that can reduce the possibility of missing the timing of light stimulation that is desired to be performed to correct the circadian rhythm.

[0011] The circadian rhythm measurement system of the present invention comprises a deep body temperature conversion unit configured to calculate a user's deep body temperature from the user's skin temperature measured by a sensor device at each first period, which is the same as the measurement period of the sensor device; a circadian rhythm conversion unit configured to calculate the latest time at which the deep body temperature reached a minimum value based on the deep body temperatures over a certain period from the past to the latest as the nadir time; and an output unit configured to notify the user of the time at which light stimulation should be performed, which is obtained by adding a predetermined time to the nadir time, and is characterized in that the circadian rhythm conversion unit calculates the nadir time at each second period, which is equal to or longer than the first period and shorter than the predetermined time.

[0012] According to the present invention, the deep body temperature conversion unit performs processing at a first period that is the same as the measurement period of the sensor device, and the circadian rhythm conversion unit performs processing at a second period that is equal to or longer than the first period but shorter than a predetermined time, thereby reducing the possibility of missing the timing of the light stimulation that is desired to be performed to correct the circadian rhythm.

[0013] FIG. 1 is a block diagram showing the configuration of a circadian rhythm measurement system according to an embodiment of the present invention. FIG. 2 is a flowchart explaining the operation of the circadian rhythm measurement system according to an embodiment of the present invention. FIG. 3 is a flowchart explaining the operation of the circadian rhythm measurement system according to an embodiment of the present invention. FIG. 4 is a diagram explaining the effect of the circadian rhythm measurement system according to an embodiment of the present invention. FIG. 5 is a block diagram showing an example of the configuration of a computer that realizes the circadian rhythm measurement system according to an embodiment of the present invention. FIG. 6 is a block diagram showing the configuration of a conventional system. FIG. 7 is a diagram explaining the problems with the conventional system.

[0014]

[0023] An embodiment of the present invention will now be described with reference to the drawings. Fig. 1 is a block diagram showing the configuration of a circadian rhythm measurement system according to this embodiment. The circadian rhythm measurement system comprises a sensor device 1 and a processing terminal 2 such as a smartphone.

[0015] The sensor device 1 includes a measurement unit 10 and a data transmission unit 11. The processing terminal 2 includes a data reception unit 20, a core body temperature conversion unit 21, a core body temperature estimation unit 22, a circadian rhythm conversion unit 23, a core body temperature nadir estimation unit 24, an output unit 25, a core body temperature estimated value storage unit 26, and a core body temperature nadir estimated value storage unit 27.

[0016] Fig. 2 is a flowchart explaining the operations of the data receiving unit 20, deep body temperature conversion unit 21, and deep body temperature estimation unit 22 of the sensor device 1 and the processing terminal 2. Fig. 3 is a flowchart explaining the operations of the circadian rhythm conversion unit 23, deep body temperature nadir estimation unit 24, output unit 25, deep body temperature estimated value holding unit 26, and deep body temperature nadir estimated value holding unit 27 of the processing terminal 2.

[0017] The measurement unit 10 of the sensor device 1 receives data T0 corresponding to the skin temperature T0 of the user, for example, on the forehead. ｒａｗ and data T1 corresponding to the temperature T1 at a position away from the user's skin. ｒａｗ The temperature T1 is the temperature inside a thermal resistor that is placed in contact with the user's skin, for example, directly above the measurement point of the skin temperature T0.

[0018] The data transmission unit 11 of the sensor device 1 receives data T0 ｒａｗ , T1 ｒａｗ is wirelessly transmitted to the processing terminal 2 (step S101 in FIG. 2).

[0019] The data receiving unit 20 of the processing terminal 2 receives the data T0 transmitted from the sensor device 1. ｒａｗ , T1 ｒａｗ (Step S102 in FIG. 2). The data receiving unit 20 receives the data T0 ｒａｗ , T1 ｒａｗ is converted into temperatures T0 and T1 (step S103 in FIG. 2). ｒａｗ , T1 ｒａｗ When the sensor of the measuring unit 10 that acquires the data is a platinum resistance thermometer, the data receiving unit 20 acquires the data T0 ｒａｗ , T1 ｒａｗ is converted into temperatures T0 and T1 using equations (1) and (2). T0 = A0 x T0 Ｒａｗ +B0...(1) T1=A1×T1 Ｒａｗ +B1...(2)

[0020] A0, B0, A1, and B1 are predetermined coefficients. Data T0 ｒａｗ , T1 ｒａｗ When the sensor of the measurement unit 10 that acquires the data T0 is a thermistor, the data receiving unit 20 ｒａｗ , T1 ｒａｗ is converted into temperatures T0 and T1 based on a resistance-temperature conversion table. If the measuring unit 10 is configured to be able to output data on temperatures T0 and T1, the data on temperatures T0 and T1 is sent from the sensor device 1. ｒａｗ , T1 ｒａｗ to temperatures T0 and T1 is not required.

[0021] The deep body temperature conversion unit 21 of the processing terminal 2 calculates the deep body temperature T ＣＢＴ (t) is calculated (step S104 in FIG. 2). ＣＢＴ (t)=T0+α×(T0-T1)...(3)

[0022] where α is a predetermined coefficient. This method of calculating core body temperature is disclosed in the document “J. Feng, et al., “Development of an improved wearable device for core body temperature monitoring based on the dual heat flux principle,” Physiological Measurement, Volume 38, Number 4, pp. 652-668, 2017.”

[0023] The deep body temperature estimation unit 22 of the processing terminal 2 converts the deep body temperature T calculated by the deep body temperature conversion unit 21 into ＣＢＴ The core body temperature estimate T obtained by removing noise from (t) ＣＢＴ _ ｋｆ (t) (Step S105 in FIG. 2). ＣＢＴ _ ｋｆ The calculation date and time information is added to (t) and stored in the core body temperature estimated value holding unit 26 .

[0024] Core body temperature T ＣＢＴ The value of (t) is superimposed with noise originating from the device due to changes in temperature and airflow, and noise originating from the living body due to changes in blood flow and deformation of the measuring unit 10. In order to avoid outputting inaccurate information, the core body temperature T ＣＢＴ Noise is removed from (t). A method of removing noise is to use a smoothing filter (Kalman filter). The input value of the Kalman filter is the latest deep body temperature T calculated by the deep body temperature conversion unit 21. ＣＢＴ (t) and the previous estimated value T ＣＢＴ _ ｋｆ (t-1). The parameters required for the Kalman filter, such as the Kalman gain, are set in advance.

[0025] The above-described processing of steps S100 to S105 is performed every time the temperature is measured by the sensor device 1. For example, if the measurement period of the sensor device 1 is one minute, the processing is performed every minute.

[0026] The circadian rhythm conversion unit 23 of the processing terminal 2 calculates the estimated deep body temperature T ＣＢＴ _ ｋｆ (t-n Ｎ ) to get the latest estimated core body temperature T ＣＢＴ _ ｋｆ The estimated core body temperature for N hours up to (t) is fitted using a model such as equation (4), which combines a 24-hour cosine function and a 12-hour cosine function (step S106 in FIG. 2). ＣＢＴ _ ｆｉｔ =a×cos(2×π×f×t-b) +c×cos(2×π×f / 2×t-d)+e...(4)

[0027] a, b, c, d, and e are fitting parameters. f is a predetermined value, and f = 1 / P (P is 24 hours). The 2-harmonic cosinor method using a model formula such as Equation (4) is disclosed in Non-Patent Document 2. The value N, which specifies the period to be fitted, is set between 6 hours, assuming short-term measurement only at night, and 48 hours, assuming measurement over multiple days. If measurement is performed only at night every day, N can be, for example, 6 hours. On the other hand, if measurement is performed all day, N must be set so that it includes at least one lowest point of the estimated core body temperature.

[0028] The circadian rhythm conversion unit 23 converts the output T ＣＢＴ _ ｆｉｔ The time when the value of the core body temperature reaches its minimum (peak value) is called the lowest point of the core body temperature t Ｔｍｉｎ (t) (Step S107 in FIG. 2). Depending on the setting of N, T ＣＢＴ _ ｆｉｔ There may be multiple times when the value of is a minimum. The latest of these times is called the lowest point time t Ｔｍｉｎ (t) can be output.

[0029] The core body temperature nadir estimating unit 24 of the processing terminal 2 calculates the nadir time t Ｔｍｉｎ The lowest point time estimate t obtained by removing outliers from (t) Ｔｍｉｎ _ｋｆ (t) (Step S108 in FIG. 2). Ｔｍｉｎ _ ｋｆ The calculation date and time information is added to (t) and stored in the core body temperature nadir estimated value holding unit 27 .

[0030] lowest point time t Ｔｍｉｎ (t) changes depending on the number of data points during fitting. For this reason, if the number of data points is extremely short, an unexpected time may be calculated. In order to avoid outputting inaccurate information, the lowest point time t Ｔｍｉｎ The outliers are removed from (t). One method for removing the outliers is to use a smoothing filter (Kalman filter). The input value of the Kalman filter is the latest lowest point time t calculated by the circadian rhythm conversion unit 23. Ｔｍｉｎ (t), and the last nadir time estimate t of the previous day stored in the core body temperature nadir estimate value storage unit 27. Ｔｍｉｎ _ ｋｆ (t-n Ｂ The parameters required for the Kalman filter, such as the Kalman gain, are set in advance.

[0031] It is desirable to switch between the previous day and the current day at a time other than near the time of the deep body temperature nadir. For example, it is possible to switch at 6:00 PM every day. If the current time is after 6:00 PM, the nadir time between 6:00 PM and 6:00 PM of the previous day is the nadir time of the previous day. The nadir time between 6:00 PM and 6:00 PM of the next day is the nadir time of the current day.

[0032] The output unit 25 of the processing terminal 2 outputs the nadir time estimate value t calculated by the core body temperature nadir estimating unit 24. Ｔｍｉｎ _ ｋｆ Based on (t), the time t at which light stimulation should be performed is determined. ｌｉｇｈｔ The output unit 25 notifies the user of the estimated nadir time t Ｔｍｉｎ _ ｋｆ When (t) is later than the user's usual core body temperature nadir time specified in advance, the nadir time estimate t Ｔｍｉｎ _ ｋｆ The time obtained by adding A time to (t) is the time t at which light stimulation should be performed. ｌｉｇｈｔThe output unit 25 notifies the user of the estimated nadir time t Ｔｍｉｎ _ ｋｆ When (t) is earlier than the user's usual core body temperature nadir time specified in advance, the nadir time estimate t Ｔｍｉｎ _ ｋｆ The time obtained by adding time B to (t) is the time t at which light stimulation should be performed. ｌｉｇｈｔ (t) is notified to the user.

[0033] A and B are set in the ranges of 1 hour≦A≦4 hours and 20 hours≦B≦23 hours based on the phase response curve to light stimulation (Non-Patent Document 1). Notification methods include display and voice notification. Note that during processing (for example, when performing all-day measurement and the time is 7 p.m.), the lowest point time estimate t Ｔｍｉｎ _ ｋｆ Although (t) may be the lowest point time of the previous day, the output unit 25 notifies the lowest point time estimate t Ｔｍｉｎ _ ｋｆ Only when (t) is the lowest point time of the day.

[0034] The processing of steps S106 to S109 above may be batch processing at a cycle shorter than the time A from the detection of the nadir time to the timing of light stimulation (for example, batch processing every 30 minutes).

[0035] FIG. 4 is a diagram illustrating the effect of this embodiment. ＣＢＴ _ ｆｉｔ The circadian rhythm conversion unit 23 calculates the estimated deep body temperature T by the 2-harmonic cosinor method. ＣＢＴ _ ｋｆ In the example of FIG. 4, the lowest point at time t Ｔｍｉｎ The data period for N hours when calculating is D1, and the lowest point time t Ｔｍｉｎ The period of data for N hours when calculating is designated as D2. However, within the period D2, there is a missing period D3 where there is no data for temperatures T0 and T1. The dotted line LT indicates the time obtained by adding 3 hours to the time of the lowest point on the vertical axis on the right.

[0036] In this embodiment, the processes of steps S100 to S105 are performed for each measurement period of the sensor device 1, and the processes of steps S106 to S109 are performed for each period shorter than time A, thereby enabling more continuous analysis than conventional methods. Ｔｍｉｎ _ ｋｆ Since analysis is possible in the vicinity of t Ｔｍｉｎ _ ｋｆ This will prevent the timing of the light stimulus from being missed after A hours.

[0037] On the other hand, at time t2, the circadian rhythm conversion unit 23 converts the estimated deep body temperature T ＣＢＴ _ ｋｆ When fitting is performed for the temperature T0 and T1, there is a missing period D3 in the data for the temperatures T0 and T1. ＣＢＴ _ ｋｆ Cosine curve T fitted to ＣＢＴ _ ｆｉｔ is the cosine curve T that should be calculated ＣＢＴ _ ｋｆ In the conventional system, an inaccurate nadir time is calculated, but in this embodiment, the core body temperature nadir estimation unit 24 estimates the core body temperature nadir, and the inaccurate nadir time is filtered out. As a result, the nadir time t that is close to the time that should be calculated is calculated. Ｔｍｉｎ _ ｋｆ can be calculated.

[0038] The processing terminal 2 described in this embodiment can be realized by a computer equipped with a CPU (Central Processing Unit), a storage device, and an interface, and a program that controls these hardware resources. An example of the configuration of this computer is shown in FIG.

[0039] The computer includes a CPU 300, a storage device 301, and an interface device (I / F) 302. The I / F 302 is connected to the hardware of the data receiving unit 20, the hardware of the output unit 25, and the like. In such a computer, a program for implementing the method of the present invention is stored in the storage device 301. The CPU 300 executes the processing described in this embodiment in accordance with the program stored in the storage device 301.

[0040] Some or all of the above embodiments can be described as, but are not limited to, the following supplementary notes.

[0041] (Appendix 1) The circadian rhythm measurement system of the present invention comprises a deep body temperature conversion unit configured to calculate the user's deep body temperature from the user's skin temperature measured by a sensor device for each first period that is the same as the measurement period of the sensor device; a circadian rhythm conversion unit configured to calculate the most recent time at which the deep body temperature reached a minimum value based on the deep body temperatures over a certain period from the past to the most recent as the nadir time; and an output unit configured to notify the user of the time obtained by adding a predetermined time to the nadir time as the time at which light stimulation should be performed, and the circadian rhythm conversion unit calculates the nadir time for each second period that is equal to or greater than the first period and shorter than the predetermined time.

[0042] (Appendix 2) The circadian rhythm measurement system described in Appendix 1 further includes a deep body temperature estimation unit between the deep body temperature conversion unit and the circadian rhythm conversion unit, configured to calculate a deep body temperature estimate value by removing noise from the deep body temperature for each second period, wherein the deep body temperature estimation unit receives as input the latest deep body temperature calculated by the deep body temperature conversion unit and the previous deep body temperature estimate value, and the circadian rhythm conversion unit calculates the latest time at which the deep body temperature estimate value reached its minimum value as the nadir time.

[0043] (Appendix 3) In the circadian rhythm measurement system described in Appendix 2, the circadian rhythm conversion unit performs fitting to approximate the estimated core body temperature value for a certain period from the past to the latest using a model, and outputs the time when the output of the model after fitting becomes a minimum value as the nadir time.

[0044] (Appendix 4) The circadian rhythm measurement system described in Appendix 1 further comprises a core body temperature nadir estimator between the circadian rhythm conversion unit and the output unit, configured to calculate, for each second period, a nadir time estimate value obtained by removing outliers from the nadir time calculated by the circadian rhythm conversion unit, wherein the core body temperature nadir estimator receives as input the latest nadir time calculated by the circadian rhythm conversion unit and the nadir time estimate value at the end of the previous day, and the output unit notifies the user of the time when light stimulation should be performed, which is the latest nadir time estimate value calculated by the core body temperature nadir estimator plus the predetermined time.

[0045] 1...sensor device, 2...processing terminal, 20...data receiving unit, 21...core body temperature conversion unit, 22...core body temperature estimation unit, 23...circadian rhythm conversion unit, 24...core body temperature nadir estimation unit, 25...output unit, 26...core body temperature estimated value holding unit, 27...core body temperature nadir estimated value holding unit.

Claims

1. A circadian rhythm measurement system comprising: a deep body temperature conversion unit configured to calculate a user's deep body temperature from the user's skin temperature measured by a sensor device at a first cycle that is the same as the measurement cycle of the sensor device; a circadian rhythm conversion unit configured to calculate the latest time at which the deep body temperature reached a minimum value based on the deep body temperatures over a certain period from the past to the latest as the nadir time; and an output unit configured to notify the user of the time obtained by adding a predetermined time to the nadir time as the time at which light stimulation should be performed, wherein the circadian rhythm conversion unit calculates the nadir time at a second cycle that is equal to or longer than the first cycle and shorter than the predetermined time.

2. A circadian rhythm measurement system as described in claim 1, further comprising a deep body temperature estimation unit between the deep body temperature conversion unit and the circadian rhythm conversion unit, configured to calculate a deep body temperature estimate value by removing noise from the deep body temperature for each of the second cycles, wherein the deep body temperature estimation unit receives as input the latest deep body temperature calculated by the deep body temperature conversion unit and the previous deep body temperature estimate value, and the circadian rhythm conversion unit calculates the latest time at which the deep body temperature estimate value reached its minimum value as the nadir time.

3. A circadian rhythm measurement system according to claim 2, wherein the circadian rhythm conversion unit performs fitting to approximate the estimated core body temperature values ​​for a certain period from the past to the latest using a model, and outputs the time when the output of the model after fitting reaches a minimum value as the nadir time.

4. A circadian rhythm measurement system as described in claim 1, further comprising a core body temperature nadir estimating unit between the circadian rhythm conversion unit and the output unit, configured to calculate, for each second period, an estimated nadir time value obtained by removing outliers from the nadir time calculated by the circadian rhythm conversion unit, wherein the core body temperature nadir estimating unit receives as input the latest nadir time calculated by the circadian rhythm conversion unit and the estimated nadir time value at the end of the previous day, and wherein the output unit notifies the user of the time obtained by adding the specified time to the latest estimated nadir time calculated by the core body temperature nadir estimating unit as the time at which light stimulation should be performed.

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