LED blue, red and green light has a potential impact on the heart
LEDs have occupied an important position in energy-efficient home appliances, headlights and street lights. Whether this new type of light source will affect human organs has attracted the attention of researchers. Over the past decade, there has been a growing interest in the non-imaging biological effects of light on the retina, such as performance and attention, sleep quality, and hormonal secretion, with particular attention being paid to the retinal channel effects of the circadian clock in the nucleus of the brain.
Due to the discovery of human third photoreceptor cell ipRGC (Intrinsically Photosensitive Retinal Ganglion Cell), the relationship between light source and human physiological health has been further emphasized. Recent studies have found that light has the function of regulating human circadian rhythm.
Brainard et al. used eight kinds of monochromatic light to illuminate the testers at night, and found that different monochromatic lights have different inhibitory effects on melatonin content, and based on the experimental results, a spectral light efficiency curve based on melatonin was drawn. Studies by Mariana et al. showed that under 40 lx red and blue light, the human heart rate increased, and the amplitude of the alpha wave in the EEG decreased under the illumination of 10 lx red and blue light, while the amplitude of the beta wave increased. By using different wavelengths of light to illuminate the human eye, Christian et al. found that short-wave illumination is more pronounced than long-wave changes in body temperature and heart rate. Chai Yingbin et al. studied the changes in heart rate of humans under low illumination (about 75 lx at the human eye) and found that there were differences in heart rate changes caused by light of different colors at low illumination levels.
All the above experimental results show that the wavelength of the light source is an important factor affecting the biological effect, indicating that light is a potential physiological, behavioral and therapeutic incentive for the human body. Recent medical and biological studies have confirmed that the natural variation in the daily content of melatonin in the blood not only affects the mental state, but may also cause serious health problems such as premature aging, sexual dysfunction, and breast cancer after prolonged accumulation.
The spectroscopy sensitivity of the sinus rhythm of the narrow-band light source has been well studied. The design of the light source has been able to guide the non-visual biological effects of light. With the popularization of artificial lighting, many cities have become the city that never sleeps, and the night is low. Illumination light also affects the physiology of human body. Based on the spectral light efficiency curve defined by Brinard et al. in the study of melatonin inhibition, the physiological effects of nighttime weak light source on human ECG (Electro-cardiograph) are analyzed through experimental tests. .
Biological rhythm factor
The various types of photoreceptor cells in the human eye respond differently to different spectral sources, and the biological rhythm factor can be introduced by the concept of luminous flux to evaluate the biological effects of light. The hollow dot in Fig. 1 is the spectral response sensitivity of human circadian rhythm according to the inhibition of melatonin by Rea et al. The visual curve B(λ) is the 4th-order fitting curve, and the visual visual curve V(λ) is the bright vision. The spectral light efficiency curve below. It can be seen from Fig. 1 that the peak of the fitted B(λ) curve is around 460 nm, which is shifted to the short-wave direction with respect to the bright-view curve V(λ), and is in the blue portion, which is the spectral band rich in most white LEDs. The biorhythm factor can be defined by the bright curve V(λ) and the fitted B(λ) curve.
According to the concept of the biological rhythm factor, the following two steps can be used to obtain the value:
1) The relative spectral power curve λ(λ) for different light sources is normalized to Ф(λ)i, norm by a uniform visual factor or uniform luminous flux (eg 100 lm), defined as follows:
Where K = 683 lm/W is the maximum luminous efficiency value under bright vision, and Фv, i represents the normalized value of a particular spectrum.
2) The rhythm factor BioEq (Biological Equivalent) is
The rhythm factor BioEq can be calculated by measuring the spectrum Ф(λ)i of different light sources by a spectrometer.
The light flux of the light source in the visible range is the size of the light source illumination value, and the size of the biological rhythm factor reflects the biological effect of the light source on the human body.
LED normalized spectrum
The light sources used in the experiment are all LEDs, which are blue, green and red at 448, 517 and 632 nm, respectively. Figure 2 shows the three types of light source measured by WGD-3 multi-function grating spectrometer. (1) Normalized spectral distribution curve. The measured spectral data V(λ) of the light source can be calculated by the equations (1) and (2) to obtain the biological rhythm factors of blue light, green light and red light, respectively, and the results are 1.7003, 0.0094, and 0.0005, respectively. The blue light has the largest BioEq value, the green light is the second, and the red light is the smallest. Compared with the luminous flux, blue light has the greatest influence on the photobiological effect of the human body, and the red light has the least influence. Accordingly, according to the spectral efficiency curve of the third photoreceptor cell, the BioEq value is used to measure the biological effects of the three color LED light sources, quantitatively analyze the size of the non-visual biological effect, and guide the analysis and comparison of the electrocardiogram experimental results.
Experimental design and data analysis
The experiment selected several test subjects to measure the same light source for three consecutive nights, and each tester only performed ECG measurement of one wavelength. The subjects were all male, no eye disease, no color blindness, corrected visual acuity was 5.0, and were required to work normally during the test. The experiment was carried out in a self-built laboratory with an ambient temperature control at 25 ° C and a sound level of around 10 dB. The subject adopts a lying posture, and the light source is distributed around the subject, so that the subject has no glare effect in the lying state, and the illuminance at the human eye reaches the desired value when lying down through the wall. .
The ECG recording was performed using the ECG-2203G three-channel electrocardiograph. This ECG machine can print the measured ECG data and directly obtain the atrial depolarization wave P wave, the ventricular depolarization wave QRS complex, the ventricular depolarization and the repolarization total time QT. Interval and correction value QTc and other ECG waveform time. The light source is a 4-inch Jihai Shi full-color LED, which can realize LED light output of different colors.
During the test, the testee lie flat for 20 min in the dark room, then turn on the LED light source set to the specified color, and lie flat for 20 min in the case of test light. The ECG is measured every 5 min during the period. The color of the light source used is red, green and blue. The illuminance value of the human eye was measured by TES's Model 1336A Light Meter. The illuminance values ​​measured in the self-built environment were 0.9 Ix for red light, 1.0 lx for blue light, and 0.9 lx for green light, all of which were extremely low illumination levels.
A total of 10 sets of data were obtained from the experiment, and each set of data contained electrocardiogram data in the absence of light and light. The data measured at the same wavelength are combined into one group, and the data in the unlit state and the glazed state are respectively averaged, and the obtained results are shown in Figs. 3(a)-(f).
In the figure, NL is an abbreviation of No Light, which indicates a measurement value when there is no light; RL is an abbreviation of Red Light, which indicates a measurement value under red light irradiation; GL is an abbreviation of Green Light, which indicates a measurement value under green light irradiation; BL Abbreviation for Blue Light, which is a measurement under blue light. The box in the figure indicates the standard deviation SD of the measured data, the middle dot indicates the average value of the measured data, and the upper and lower horizontal short lines indicate the maximum and minimum values ​​of the measured value. Tp, TQRS, TT, TQT represent the time intervals of each wave.
Fig. 3(a) and Fig. 3(b) show that different light sources have little effect on the P wave time and QRS group time of human ECG, and the independence t test shows that there is no difference in the values ​​of no light and light. .
Figure 3(c) shows that the T-wave time reflecting the rapid repolarization of the late ventricular phase increases in red and green light, and the T-wave time in green light increases by an average of 4 ms (parameter t=-2.279, P =0.036), while under blue light it shows a drop.
It can be seen from Fig. 3(d) that the QT interval under red and green light is significantly increased (red light average increases by 5 ms, t=-2.202, P=0.04, green light increases by 7 ms). , t=-2.829, P=0.012), there is basically no change under blue light, because the QT interval represents the total time of depolarization to repolarization of the ventricle, which indicates that the wavelength of the light source has a non-negligible influence on ventricular activity.
Figure 3(e) shows that the QTc value increases with different light sources, with red and green light increasing by about 2 ms, while blue light test results show an increase of 6 ms, but independence is detected. Both indicate that there is no difference between the data under the light and the data under the three light sources.
Figure 3(f) shows that red and green light have little effect on ventricular rate under very low illumination, while ventricular rate under blue light shows signs of acceleration (average increase of 2 times, t=-2.456, P=0.022) .
From the results of other researchers, the effect on the ventricular rate at 75 lx was blue>green>red light, and the calculated BioEq values ​​were blue light 1.705, green light 0.094, red light 0.0005, respectively. It also shows that the biological effects of blue light have the greatest influence. In the experimental results, the ventricular rate of blue light increases and there is a difference, which indicates that the effect of blue light on ventricular rate still exists in the illumination of 1 lx level, while the influence of red light and green light still exists. It has been weak to no effect.
It is shown in the literature that the effects of short-wavelength light on human physiology (melatonin, heart rate) at different illuminance values ​​are longer than those of BioEq, but the results of QE are more consistent in this experiment. In the opposite state, the order of the average is red light>green light>blue light, and the data under red and green light is different, while the blue light has no difference. The reason for this is that the BioEq value is calculated using a fourth-order fitting curve based on melatonin inhibition data, which may have certain limitations for the degree of biological effects used to describe light. From the experimental results, the low-illuminance light source has a greater influence on the ventricular rate, while the long-wavelength light source has a greater influence on the QT value.
in conclusion
The experimental results show that the LED light source has a potential impact on the ECG index of the heart under extremely low illumination, which has a great influence on the QT value and ventricular rate. The blue light band has a greater influence on heart rate, and the influence of red and green light on QT value is more obvious. The experimental results differed from the calculated biorhythm factor BioEq in the trend of QT values, partly due to the calculation of BioEq based on experimental data of melatonin inhibition, reflecting the spectral inhibitor of melatonin, which was used to evaluate the non-light. The visual biological effect is one-sided, and the theoretical evaluation method needs to be improved.
Due to the discovery of human third photoreceptor cell ipRGC (Intrinsically Photosensitive Retinal Ganglion Cell), the relationship between light source and human physiological health has been further emphasized. Recent studies have found that light has the function of regulating human circadian rhythm.
Brainard et al. used eight kinds of monochromatic light to illuminate the testers at night, and found that different monochromatic lights have different inhibitory effects on melatonin content, and based on the experimental results, a spectral light efficiency curve based on melatonin was drawn. Studies by Mariana et al. showed that under 40 lx red and blue light, the human heart rate increased, and the amplitude of the alpha wave in the EEG decreased under the illumination of 10 lx red and blue light, while the amplitude of the beta wave increased. By using different wavelengths of light to illuminate the human eye, Christian et al. found that short-wave illumination is more pronounced than long-wave changes in body temperature and heart rate. Chai Yingbin et al. studied the changes in heart rate of humans under low illumination (about 75 lx at the human eye) and found that there were differences in heart rate changes caused by light of different colors at low illumination levels.
All the above experimental results show that the wavelength of the light source is an important factor affecting the biological effect, indicating that light is a potential physiological, behavioral and therapeutic incentive for the human body. Recent medical and biological studies have confirmed that the natural variation in the daily content of melatonin in the blood not only affects the mental state, but may also cause serious health problems such as premature aging, sexual dysfunction, and breast cancer after prolonged accumulation.
The spectroscopy sensitivity of the sinus rhythm of the narrow-band light source has been well studied. The design of the light source has been able to guide the non-visual biological effects of light. With the popularization of artificial lighting, many cities have become the city that never sleeps, and the night is low. Illumination light also affects the physiology of human body. Based on the spectral light efficiency curve defined by Brinard et al. in the study of melatonin inhibition, the physiological effects of nighttime weak light source on human ECG (Electro-cardiograph) are analyzed through experimental tests. .
Biological rhythm factor
The various types of photoreceptor cells in the human eye respond differently to different spectral sources, and the biological rhythm factor can be introduced by the concept of luminous flux to evaluate the biological effects of light. The hollow dot in Fig. 1 is the spectral response sensitivity of human circadian rhythm according to the inhibition of melatonin by Rea et al. The visual curve B(λ) is the 4th-order fitting curve, and the visual visual curve V(λ) is the bright vision. The spectral light efficiency curve below. It can be seen from Fig. 1 that the peak of the fitted B(λ) curve is around 460 nm, which is shifted to the short-wave direction with respect to the bright-view curve V(λ), and is in the blue portion, which is the spectral band rich in most white LEDs. The biorhythm factor can be defined by the bright curve V(λ) and the fitted B(λ) curve.
According to the concept of the biological rhythm factor, the following two steps can be used to obtain the value:
1) The relative spectral power curve λ(λ) for different light sources is normalized to Ф(λ)i, norm by a uniform visual factor or uniform luminous flux (eg 100 lm), defined as follows:
Where K = 683 lm/W is the maximum luminous efficiency value under bright vision, and Фv, i represents the normalized value of a particular spectrum.
2) The rhythm factor BioEq (Biological Equivalent) is
The rhythm factor BioEq can be calculated by measuring the spectrum Ф(λ)i of different light sources by a spectrometer.
The light flux of the light source in the visible range is the size of the light source illumination value, and the size of the biological rhythm factor reflects the biological effect of the light source on the human body.
LED normalized spectrum
The light sources used in the experiment are all LEDs, which are blue, green and red at 448, 517 and 632 nm, respectively. Figure 2 shows the three types of light source measured by WGD-3 multi-function grating spectrometer. (1) Normalized spectral distribution curve. The measured spectral data V(λ) of the light source can be calculated by the equations (1) and (2) to obtain the biological rhythm factors of blue light, green light and red light, respectively, and the results are 1.7003, 0.0094, and 0.0005, respectively. The blue light has the largest BioEq value, the green light is the second, and the red light is the smallest. Compared with the luminous flux, blue light has the greatest influence on the photobiological effect of the human body, and the red light has the least influence. Accordingly, according to the spectral efficiency curve of the third photoreceptor cell, the BioEq value is used to measure the biological effects of the three color LED light sources, quantitatively analyze the size of the non-visual biological effect, and guide the analysis and comparison of the electrocardiogram experimental results.
Experimental design and data analysis
The experiment selected several test subjects to measure the same light source for three consecutive nights, and each tester only performed ECG measurement of one wavelength. The subjects were all male, no eye disease, no color blindness, corrected visual acuity was 5.0, and were required to work normally during the test. The experiment was carried out in a self-built laboratory with an ambient temperature control at 25 ° C and a sound level of around 10 dB. The subject adopts a lying posture, and the light source is distributed around the subject, so that the subject has no glare effect in the lying state, and the illuminance at the human eye reaches the desired value when lying down through the wall. .
The ECG recording was performed using the ECG-2203G three-channel electrocardiograph. This ECG machine can print the measured ECG data and directly obtain the atrial depolarization wave P wave, the ventricular depolarization wave QRS complex, the ventricular depolarization and the repolarization total time QT. Interval and correction value QTc and other ECG waveform time. The light source is a 4-inch Jihai Shi full-color LED, which can realize LED light output of different colors.
During the test, the testee lie flat for 20 min in the dark room, then turn on the LED light source set to the specified color, and lie flat for 20 min in the case of test light. The ECG is measured every 5 min during the period. The color of the light source used is red, green and blue. The illuminance value of the human eye was measured by TES's Model 1336A Light Meter. The illuminance values ​​measured in the self-built environment were 0.9 Ix for red light, 1.0 lx for blue light, and 0.9 lx for green light, all of which were extremely low illumination levels.
A total of 10 sets of data were obtained from the experiment, and each set of data contained electrocardiogram data in the absence of light and light. The data measured at the same wavelength are combined into one group, and the data in the unlit state and the glazed state are respectively averaged, and the obtained results are shown in Figs. 3(a)-(f).
In the figure, NL is an abbreviation of No Light, which indicates a measurement value when there is no light; RL is an abbreviation of Red Light, which indicates a measurement value under red light irradiation; GL is an abbreviation of Green Light, which indicates a measurement value under green light irradiation; BL Abbreviation for Blue Light, which is a measurement under blue light. The box in the figure indicates the standard deviation SD of the measured data, the middle dot indicates the average value of the measured data, and the upper and lower horizontal short lines indicate the maximum and minimum values ​​of the measured value. Tp, TQRS, TT, TQT represent the time intervals of each wave.
Fig. 3(a) and Fig. 3(b) show that different light sources have little effect on the P wave time and QRS group time of human ECG, and the independence t test shows that there is no difference in the values ​​of no light and light. .
Figure 3(c) shows that the T-wave time reflecting the rapid repolarization of the late ventricular phase increases in red and green light, and the T-wave time in green light increases by an average of 4 ms (parameter t=-2.279, P =0.036), while under blue light it shows a drop.
It can be seen from Fig. 3(d) that the QT interval under red and green light is significantly increased (red light average increases by 5 ms, t=-2.202, P=0.04, green light increases by 7 ms). , t=-2.829, P=0.012), there is basically no change under blue light, because the QT interval represents the total time of depolarization to repolarization of the ventricle, which indicates that the wavelength of the light source has a non-negligible influence on ventricular activity.
Figure 3(e) shows that the QTc value increases with different light sources, with red and green light increasing by about 2 ms, while blue light test results show an increase of 6 ms, but independence is detected. Both indicate that there is no difference between the data under the light and the data under the three light sources.
Figure 3(f) shows that red and green light have little effect on ventricular rate under very low illumination, while ventricular rate under blue light shows signs of acceleration (average increase of 2 times, t=-2.456, P=0.022) .
Table 1-3 shows the test value comparison and the independence t test result when the LED light source is turned on and when there is no light. It can be seen from Tables 1-3 that there are significant differences in QT values ​​under red and green light, T values ​​under green light, and ventricular rates under blue light.
From the results of other researchers, the effect on the ventricular rate at 75 lx was blue>green>red light, and the calculated BioEq values ​​were blue light 1.705, green light 0.094, red light 0.0005, respectively. It also shows that the biological effects of blue light have the greatest influence. In the experimental results, the ventricular rate of blue light increases and there is a difference, which indicates that the effect of blue light on ventricular rate still exists in the illumination of 1 lx level, while the influence of red light and green light still exists. It has been weak to no effect.
It is shown in the literature that the effects of short-wavelength light on human physiology (melatonin, heart rate) at different illuminance values ​​are longer than those of BioEq, but the results of QE are more consistent in this experiment. In the opposite state, the order of the average is red light>green light>blue light, and the data under red and green light is different, while the blue light has no difference. The reason for this is that the BioEq value is calculated using a fourth-order fitting curve based on melatonin inhibition data, which may have certain limitations for the degree of biological effects used to describe light. From the experimental results, the low-illuminance light source has a greater influence on the ventricular rate, while the long-wavelength light source has a greater influence on the QT value.
in conclusion
The experimental results show that the LED light source has a potential impact on the ECG index of the heart under extremely low illumination, which has a great influence on the QT value and ventricular rate. The blue light band has a greater influence on heart rate, and the influence of red and green light on QT value is more obvious. The experimental results differed from the calculated biorhythm factor BioEq in the trend of QT values, partly due to the calculation of BioEq based on experimental data of melatonin inhibition, reflecting the spectral inhibitor of melatonin, which was used to evaluate the non-light. The visual biological effect is one-sided, and the theoretical evaluation method needs to be improved.
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