We developed a smart-phone based system to measure the activities of autonomic nervous system during everyday life. Using commonly marketed smart phones, by touching your fingertips on the phone’s camera over a short time of about 30 seconds, it will detect changes in the brightness of the blood flow and in turn analyze your heart rate variability. By using this system, about 100,000 cases were measured and from this large amount of data regarding heart rate variability, we evaluated the autonomic nervous function in their daily life. As a result, for the correlation between autonomic nervous system and age, we found that as the increase of age, the total power becomes decreased and the sympathetic nervous system tends to increase between thirties and fifties. For the correla-tion between autonomic nervous system and BMI (Body Mass Index), it is found that in general, the higher the BMI, the lower the total power and the stronger the sympathetic nervous system. In other words, people who are fat are lower about the total power and stronger about the sympathetic nervous system. In addition, for the correlation between autonomic nervous system and one day life, it is that found that total power and sympathetic function tend to increase, while as evening ap-proaches, sympathetic function tends to become suppressed.
It is extremely important to check health conditions scientifically in daily life as Japan is facing a super-aging society problem. For which, we need to consider our health during living at home, city, and/or workplaces under all kinds of conditions of the weather, gender, aging, et al., but not only dependent on hospital. It is clear that, when people are continuously subjected to large amounts of stress for long periods of time throughout their everyday lives, it will cause abnormalities of their autonomic nervous systems [
This system has been released as an iPhone application from Apple Inc. [
In a previous study, researchers used special pulse wave sensors and small heart rate sensors and reported that the total power―the amount of activity―of the autonomic nervous system decreases with age [
1) CORRELATION BETWEEN THE AUTONOMIC FUNCTION AND AGE.
2) CORRELATION BETWEEN THE AUTONOMIC FUNCTION AND BMI.
3) CORRELATION BETWEEN THE AUTONOMIC FUNCTION AND CIRCADIAN VARIATION.
Overview of the system we developed is shown in
smart phone as the client terminal, and a server for analysis processing. The system is being built using Java and Objective-C.
Each time when humans breathe, the amount of hemoglobin contained in the blood rises and falls, and as a consequence, the color (brightness) of the fingertip skin changes subtly [
The flow of analysis in the system is shown in
Next, in the step of “2-1 Outlier removal logic of RR interval” in “2. Autonomic nervous system analysis engine”, values are filtered by the difference from the average value of the most recent RR interval, RR interval value that exceeds a certain thresholds is estimated as an outlier value. Furthermore, a low pass filter is applied to the obtained RR interval waveform (“2-2 Low-pass filter”), high frequency noise is removed, frequency analysis is performed on the RR interval waveform in “2-3 Frequency Analysis Algorithm”, and the autonomic index is calculated. The calculation method of the autonomic nervous index conforms to the procedures of the paper [
(A series of analysis algorithms are patent pending.) A supplementary explanation of the processing is given below.
[1-2 Peak Detection Algorithm]
The RR interval waveform (peak interval waveform) is acquired by estimating the peaks to be the points upon the smoothed luminance waveform at which the value of the first order differential is zero, and the value of the second order differential becomes negative.
[2-1 Outlier removal logic of RR interval]
[STEP1]
Calculate mean HR (X) as the moving average of X heartbeats when the heart rate HR satisfies equation (1)
where
HR(n) is the nth heart rate,
Mean HR (X) is the moving average of the heart rate HR of X heartbeats.
[STEP2]
A heart rate (its corresponding RR interval) that exceeds the range of equation (2) is excluded as an error value.
In this study, the variables are set at X = 8, Y = 15, and Z = 30.
These parameters conform to values used in the authors’ previous studies [
[2-3 Frequency Analysis Algorithm]
In general, fluctuations occur in the heart rate of living bodies, and peaks can be seen at certain frequencies in a spectral analysis of the RR interval waveform. In humans, a high frequency component (0.15 Hz - 0.40 Hz: HF), which represents variations in the respiratory cycle, and a low frequency component (0.05 Hz - 0.15 Hz: LF), which reflects fluctuations in blood pressure, are seen, with both of these reflecting autonomic nervous activity. HF is believed to respond to parasympathetic innervation, while LF responds to both sympathetic and parasympathetic innervation, and LF/HF reflects sympathetic function [
In order to verify the accuracy of the heart rate to check the variability analysis system using a smart-phone camera developed in this study, precision comparison was applied using dedicated fingertip pulse wave sensor system [
The correlation diagram of the autonomic balance (ratio of the sympathetic and parasympathetic nervous systems), when the simultaneous measurements were carried out with a fingertip pulse wave sensor and smart- phone camera, is shown in
In addition, the correlation diagram of the amount of activity of the autonomic nervous system, which is the sum of the sympathetic and parasympathetic systems, is shown in
Finally,
It is then clear that our system can realize the similar precision of the measurement compared with that of the fingertip pulse wave sensor. Moreover, our system can be easily used to obtain the tendencies of the autonomic nervous state during everyday life.
Here, we analyzed autonomic data measured by heart rate variability analysis system [
camera. Frequency analysis technique is in accordance with the procedure of the paper [
The value of LF/HF is used as an indicator of the sympathetic nervous function, as an indicator of tension, excitement, stress [
In addition, the sum of the LF and HF is called total power (TP), it is an index representing the activity of the autonomic nervous system [
In this study we performed analysis based on the autonomic nervous system data of 27,307 people (male: 6394, female: 20,913). Regarding the use of the measurement data, we have the consent of the measured person, based on the Code of Ethics of WIN Frontier Corporation.
In
Age | Man | Female | Total |
---|---|---|---|
10’s | 1058 | 9448 | 10,506 |
20’s | 1433 | 7621 | 9054 |
30’s | 1342 | 1856 | 3198 |
40’s | 1406 | 1404 | 2810 |
50’s | 884 | 528 | 1412 |
Over 60’s | 271 | 56 | 327 |
Total | 6394 | 20,913 | 27,307 |
In this section, we investigated the relationship between autonomic function and age. The contents of the measurement data used in this analysis are shown in
When the logarithm was taken for the total power, the activity index of the autonomic nervous system that normality increases [
Then, we classified them in six groups starting from teens to 60 s and over, and in order to investigate the difference between groups, multiple comparisons were performed using the Games-Howell method [
As a result, as the age of the group increases, the total power was reduced significantly. This trend was also seen similarly in the case of both genders.
In previous studies of [
Then, the correlation between the LF/HF and age has been examined, as an indicator of the sympathetic nervous function. When the logarithm was taken of the LF/HF of each measurement data, since it is normality increases [
Age | Man | Female | Total |
---|---|---|---|
10’s | 3977 | 33,047 | 37,024 |
20’s | 5795 | 30,449 | 36,244 |
30’s | 9379 | 11,759 | 21,138 |
40’s | 9459 | 12,194 | 21,653 |
50’s | 7671 | 4717 | 12,388 |
Over 60’s | 1749 | 452 | 2201 |
Total | 38,030 | 92,618 | 130,648 |
The results are shown in
The increase of sympathetic nerve function in the ages of 30 - 50 s is thought to be caused by a variety of
factors, not only physiological aging changes, but also a possibility that environmental factors are significantly involved.
More than young people in 20, in the case of people in their 30 - 50 s, with marriage, childbirth and work, their social responsibility increases. This is the period of big environmental changes. Such environmental influences are also considered likely to affect the autonomic nervous system.
On the other hand, the reason that sympathetic nerve function is suppressed in people in their 60 s or over can be attributed to many people celebrating their age of retirement, that the stress from work has been reduced, this is a generation that maintains their peace of mind.
In this section, we investigated the correlation between total power and BMI. The BMI is ratio of body weight to the square of the height. It is a body mass index that represents the degree of obesity of people. In addition, according to the criteria of the paper [
The obesity index of the subjects used in this analysis and the contents of the measurement data are shown in
In previous studies that examined the BMI and total power [
Then, the correlation between the LF/HF, which is an indicator of sympathetic function, and BMI was examined. The LF/HF of each measurement data was log transformed (LnLF/HF), and they were subjected to multiple comparison by the Games-Howell method [
In this section, the correlation between autonomic function and circadian variation was examined. Here each day was separated into eight sections of three hours each, and they were subjected to analysis. The contents of the
BMI | Degree of obesity |
---|---|
Under 18.5 | Low body weight |
18.5 - 25 | Standard |
25 - 30 | Obesity (1 degree) |
30 - 35 | Obesity (2 degree) |
35 - 40 | Obesity (3 degree) |
Over 40 | Obesity (4 degree) |
Degree of obesity | Man | Female | Total |
---|---|---|---|
Low body weight | 407 | 3073 | 3480 |
Standard | 4662 | 16,249 | 20,911 |
Obesity (1 degree) | 1049 | 1232 | 2281 |
Obesity (over 2 degree) | 276 | 359 | 635 |
Total | 6394 | 20,913 | 27,307 |
Degree of obesity | Man | Female | Total |
---|---|---|---|
Low body weight | 1741 | 13,010 | 14,751 |
Standard | 29,687 | 71,984 | 101,671 |
Obesity (1 degree) | 5468 | 5803 | 11,271 |
Obesity (over 2 degree) | 1134 | 1821 | 2955 |
Total | 38,030 | 92,618 | 130,648 |
Time zone | Man | Female | Total |
---|---|---|---|
0-3 o’clock | 3428 | 10,617 | 14,045 |
3-6 o’clock | 1295 | 2949 | 4244 |
6-9 o’clock | 4716 | 8653 | 13,369 |
9-12 o’clock | 4267 | 9323 | 13,590 |
12-15 o’clock | 5064 | 10,516 | 15,580 |
15-18 o’clock | 4862 | 10,776 | 15,638 |
18-21 o’clock | 6195 | 16,617 | 22,812 |
21-24 o’clock | 8203 | 23,167 | 31,370 |
Total | 38,030 | 92,618 | 130,648 |
measured data used in this analysis are shown in
The results are shown in
In addition, saliva cortisol, which is said to correlate with adrenal fatigue, is said to show circadian variation as it has the highest value early in the morning, and has the lowest value at night [
Next, the LF/HF of each measurement data was log transformed (LnLF/HF), and they were subjected to multiple comparison by the Games-Howell method [
As a result, it has been observed that early in the morning the sympathetic nerve function tends to be significantly increased, and as night comes on, the sympathetic function tends to be suppressed. This trend was seen similarly in both genders.
In previous studies, regarding the circadian variation of autonomic function, it was observed that sympathetic function becomes higher through the day from the morning, and over the evening, in reverse, the sympathetic nerve function tends to be suppressed, the results of the present study present a matching tendency.
We developed a system in this study that allows the measuring of the tendencies of the autonomic nervous system conveniently in our everyday life. Using commonly marketed smart phones, by touching your fingertips on your phone’s camera over a short period of about 30 seconds, it will detect changes in the brightness of the blood flow and analyze your heart rate variability. When comparing with the heart rate variability analysis system using the dedicated fingertip pulse wave sensors, it shows that there is a correlation of approximately 80%
[
Makoto Komazawa,Kenichi Itao,Hiroyuki Kobayashi,Zhiwei Luo, (2016) Measurement and Evaluation of the Autonomic Nervous Function in Daily Life. Health,08,959-970. doi: 10.4236/health.2016.810099