Does exposure to an artificial ULF magnetic field affect blood pressure, heart rate variability and mood?

BIOMEDICINE PtiARMACOIHERAPY

ELSEVIER

Biomedicine & Pharmacotherapy 58 (2004) $20-$27 www.elsevier.com/locate/biopha

Does exposure to an artificial ULF magnetic field affect blood pressure, heart rate variability and mood? Gen Mitsutake a, Kuniaki Otsuka a,*, Sachiko Oinuma a, Ian Ferguson b, Germaine Corndlissen c, James Wanliss d, Franz Halberg c "Division of Neurocardiology and Chronoecology, Tokyo Women'sMedical University, Daini Hospital, Tokyo, Japan bDepartment of Geological Sciences, Universityof Manitoba, Winnipeg, MB, Canada cChronobiology Laboratories, Universityof Minnesota, Minneapolis, MN, USA dDepartment of Physical Science, Embry-Riddle Aeronautical University, Daytona Beach, FL, USA

Abstract The aim of this study was to determine whether an artificial magnetic field with an amplitude and frequency equivalent to those of geomagnetic pulsations during geomagnetic storms could affect physiology and psychology. Three healthy volunteers wore an ambulatory BP monitor and an ECG recorder around the clock for 12 consecutive weekends in Winnipeg, Manitoba, Canada. In a room shielded against ELF and VLF waves, they were exposed for 8 hours per week to either a 50 nT 0.0016 Hz or a sham magnetic field at one of six circadian stages. Real exposure randomly alternated with sham exposure. They provided saliva and recorded mood and reaction time every 4 hours while awake. Systolic (S) and diastolic (D) blood pressure (BP), and heart rate (HR) were recorded every 30 minutes. Spectral analysis of HR variability (HRV) was performed using the maximum entropy method and a complex demodulation method. For these variables, daily means were compared between real and sham exposure, using paired t-tests. Their circadian MESOR, amplitude, and acrophase were analyzed and summarized using single cosinor and population-mean cosinor. Circadian rhythms were demonstrated for HR, SBP, DBP for sham exposure, salivary flow rate, positive affect, vigor, and subjective alermess (p<0.001, -0.02). One participant showed higher HR, lower LF, HF, and VLF powers, and a steeper power-law slope (p<0.005, ~0.0001) in an early night exposure to the real magnetic field, but not in other circadian stages. There was no significant difference between circadian responses to real and sham exposure in any variable at any circadian stage. © 2004 Elsevier SAS. All rights reserved. Keywords: Circadian rhythm; Geomagnetics; Heart rate variability

1. Introduction Studies of some parameters of the blood system of rats exposed to magnetic fields in the frequency band of 0.01 to 100 Hz (with magnitudes of 5, 50, and 5000 nT) revealed that magnetic fields at frequencies of 0.02, 0.5-0.6, 5-6, and 8-11 Hz were the most bio-effective, suggesting that electromagnetic fields at ultra-low frequencies (ULF; 0 - 1 0 Hz), including those of geomagnetic pulsations, are more bioeffective than 'the power line' E L F (10-300 Hz) magnetic field [20]. There are some reports on the effects of the geo-

*Corresponding author. E-mail address: [email protected](K. Otsuka)

© 2004 Elsevier SAS. Tous droits r6servts.

magnetic field activity on both human physiology and behavior [1-13; 15-20; 22,23]. According to Ptitsyna et al. [20], U L F magnetic fields may produce effects on the nervous system and might be associated with cardiovascular disease, and that living systems including humans may have a special sensitivity to geomagnetic fields because the magnetor e c e p t i o n o f neural structures s h o u l d be e v o l u t i o n a r i l y adjusted to these fields. M o r e o v e r , we (KO) found that enhanced ambient U L F waves during geomagnetic disturbances could reduce heart rate variability (HRV) in humans [16]. Thus, existing literature suggests a link between geomagnetic pulsations and human physiology and behavior. The aim of the current study was to examine whether any effect could be documented by exposure to artificial U L F

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waves that approximated geomagnetic pulsations during magnetic storms.

2. Study aim The aim of the current study was to determine whether an artificially generated weak ULF magnetic field with an amplitude and frequency equivalent to that of naturally occurring geomagnetic pulsations during geomagnetic storms could affect HRV and circadian rhythm of systolic (S) and diastolic (D) blood pressure (BP), heart rate (HR), mood, estimated time intervals of 60 seconds (TE), reaction time (RT), and salivary flow rate (FR) and to examine whether any response to the ULF magnetic field was circadian stage-dependent.

3. Subjects and methods 3.1. Participant recruitment

Three clinically healthy male students (21 to 35 years of age) from Winnipeg, Manitoba, Canada, agreed to participate in the study. The study was approved by the University of Manitoba Research Ethics Board, and the participants were informed of the procedures and signed a consent form which guaranteed their anonymity and freedom to withdraw from the trial at any time. 3.2. Overall procedure

The participants were exposed for 8 hours per week to a 50 nT ULF magnetic field (0.0016 Hz) for 12 consecutive weekends in a magnetically shielded room. Real exposure randomly alternated with sham exposure. The exposure to the ULF magnetic field was carried out at one of six different circadian stages (i.e. from 3:00-11:00 h, 7:00-15:00 h, 11:00-19:00 h, 15:00-23:00 h, 19:00-3:00 h, and 23:007:00 h) in the room. The participants estimated their mood and time intervals of 60 seconds, and provided unstimulated whole saliva samples during waking hours for each 24-hour monitoring session. They were asked to avoid drinking coffee or alcoholic beverages during the study.

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wire. The coils were connected to a function generator (Stanford Research Systems Model DS345 Function & Arbitrary Waveform Generator, Stanford Research Systems, Sunnyvale, CA) outside the room. Protection was provided to prevent the field from exceeding 50 nT with fuses and a breaker. Two investigators continuously monitored the current in the coils, using a Tektronix Model TDS210 Digital Oscilloscope (Tektronix, Beaverton, OR). 3.4. Measurement of ELF magnetic field exposure

Personal ELF frequency (40-800 Hz) magnetic field exposure for one of the three participants was measured with an EMDEX-II meter (Enertech Consultants, Campbell, CA) during six out of 12 experimental sessions. The mean ELF magnetic field for each of the six experimental sessions ranged from 47 to 56 nT. The percentage of time when the participant was exposed to ELF magnetic fields of 40 nT or greater varied between 97.4% and 99.8%. 3.5. ECG monitoring

HRV was monitored with either a 5-lead Holter monitor (SM-50 ambulatory ECG Recorder; Fukuda Denshi; Tokyo, Japan), or a 3-lead ECG monitor (GMS Model AC-301 Active Tracer, GMS, Tokyo, Japan). Time and frequency domain measures of HRV were later calculated from the ECG data from two out of the three participants. For time domain measures of HRV, the mean cycle length of the normal-normal RR intervals (NN) and its standard deviation (SDNN) were computed and averaged over consecutive 5minutes intervals to cover each 24-hour ECG recording. The maximum entropy method (MEM) with the MemCalc/CHIRAM program (Suwa Trust Co. Ltd., Tokyo, Japan) and a complex demodulation method (CDM) [14] were used to obtain frequency domain measures of HRV. Five-minute time series of NN intervals were processed consecutively and the spectral powers in the very low frequency (VLF: 0.003-0.04 Hz), low frequency (LF: 0.04-0.15 Hz), and high frequency (HF: 0.15-0.40 Hz) regions of the spectra, as well as the LF/I-IF ratio, were calculated. The ultra-low frequency (ULF: 0.0001-0.003 Hz) component and the powerlaw slope (l/f: 0.0001-0.01 Hz) were estimated by processing 180-minute NN interval time series.

3.3. Exposure to the ULF magnetic field 3.6. Blood pressure monitoring

During each monitoring session, the participants stayed for 24 hours, except for the time taken for meals, in a wooden bed in a magnetically shielded room (interior dimensions: 3 m widthx3 m depthx3 m height) shielded against ELF and VLF waves only. The room temperature was kept at about 23 °C, and all illuminations in the room were turned off during the night (i.e. 23:00-7:00 h). The beds in the room were each located between a pair of custom-built Helmholtz coils 95 cm in radius with 12 turns (N) of enameled copper

Systolic (S) and diastolic (D) blood pressure (BP), and heart rate (HR) were automatically measured every half an hour with a commercially available ambulatory BP recorder (Model 2421, A&D Co. Ltd., Tokyo, Japan) during each monitoring session. Stored BP data were retrieved and downloaded to a personal computer with software (Model TM2430-15) commercially available from A&D Co., Ltd., Tokyo, Japan.

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3.7. Time estimation and measurements o f mood, reaction time, and salivary f l o w rate

Time intervals of 60 seconds (TE) were estimated at about 30-minute intervals during waking hours of each session, by silently counting to 60. Mood, reaction time, and unstimulated salivary flow rate were measured at about 7:00, 11:00, 15:00, 19:00, and 23:00 h. Mood was rated on the Positive and Negative Affect Schedule (PANAS) [24], the State-Trait-Cheerfulness-Inventory Short State Form (STCI-S<18>) [21], the Mood and Vigor Scale, and the Stanford Sleepiness Scale (SSS) which is available at http: / / w w w . s t a n f o r d . e d u / ~ d e m e n t / s s s . h t m l . RT was measured with free computer software, Reaction Timer, which is available from Silicon Chip Publications at: http://www.siliconchip.com.au/software/reaction.zip. Using the software on a personal notebook computer, the participants responded to a visual stimulus (a 2x3 cm red area on the computer display) by pressing the space bar as quickly as possible with their dominant hand for 10 trials in a row. Each of four-hourly RT was calculated as the mean response time to the visual stimulus. FR was calculated as mean salivary volume per minute. 3.8. Mood scales

PANAS consists of two 10-item mood scales - one for positive affect (PA) and the other for negative affect (NA). The two are reportedly highly internally consistent and largely uncorrelated and stable. The STCI-S<18> is aimed at measuring the construct of cheerfulness as a state. The scale consists of 18 items that measure cheerfulness (CH), seriousness (SE), and bad mood (BM). The Stanford Sleepiness Scale (SSS) is an 8-point scale to assess alertness. The Mood and Vigor Scales consist of two 7-point scales, which measure mood and vigor respectively. 3.9. Analyses

All these variables, except for HRV data, were analyzed by single cosinor at a trial period of 24 hours for each session by each participant. Estimates of MESOR, amplitude, and acrophase were further summarized by populationmean cosinor. For the HRV data, daily means were compared between spans of real and sham exposure to see if there is any difference in physiological responses to the magnetic field exposure, using paired t-tests at a significance level of 0.05. The HRV data were further analyzed by dividing each monitoring session into nine sampling intervals (i.e. a 1-hour interval preceding the exposure, followed by 1-, 2-, 2-, and 3hour during exposure, 1-, 2-, 6-, and 7-hour of post exposure). The spectral powers of HRV components were each compared between real and sham exposure, by using Student's t-test at a significance level of 0.001.

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4. Results

As shown in Table 1, a circadian rhythm was demonstrated under both real and sham exposure for HR (P<0.001 for both real and sham exposure conditions), SBP (P<0.001 for real exposure; P=0.002 for sham exposure), DBP (P=0.002 for sham exposure), and FR (P=0.001 for real exposure; P=0.02 for sham exposure). As shown in Table 2, a circadian rhythm was also demonstrated for PA (P=0.002 for real exposure; P=0.015 for sham exposure), V (P=0.004 for real exposure; P =0.006 for sham exposure), and SSS (P<0.001 for real exposure; P=0.001 for sham exposure). CH, although non-significant, showed a circadian rhythm with borderline significance of P=0.083 for real exposure and P=0.081 for sham exposure. Neither SE, BM, nor NA showed circadian rhythm. There was no statistically significant difference between responses to real and sham exposure in any spectral power of HRV components (see Table 3). Likewise, no significant difference was found in any circadian endpoint of either V, SSS, RT, TE, FL, or any circadian mood variables, except for the circadian acrophase of bad mood (t=3.62, df=7, P=0.01; see Table 4). Further analyses of each participant' s HRV data in which each monitoring session was divided into nine sampling intervals also showed mixed results. As shown in Figs 1 to 5, P a r t i c i p a n t - B s h o w e d h i g h e r H R , l o w e r V L F (P=0.001-0.026), LF (P<0.001~0.005), HF, and powers, and a steeper power-law slope (P<0.005-0.0001) in an early night exposure (i.e. 21:00-5:00) to the real magnetic field, compared to sham exposure, but not in other circadian stages. There was no significant difference between circadian responses to real and sham exposure in any variable at any

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Table i Population-meancos±norsummaryof blood pressure, heart rate, and salivaryflow rate Variable Real Exposure SBP= DBPb HRc FRd Sham Exposure SBPa DBP b HR~ FRa

PRe (%)

Pf

MESORg ± SEh

Amolitudei (95%

23.7 17.9 22.5 45.1

<.001 .088 <.001 <.00l

114.455 ± 3.84 72.865 ± 3.44 62.764 ± 2.56 0.583 ± 0.48

6.57 3.03 7.06 0.11

(4.17, 8.97) (0, 0) (5.15, 8.97) (0.03, 0.22)

-269 -241 -269 -215

(-254, -286) (0, 0) (-255, -283) (-194, -285)

22.9 16.0 21.9 48.5

.002 ,002 <.001 .020

115.714±3.70 71.84+2.99 61.071±2.32 0.295±0.07

7.15 4.06 6.30 0.08

(3.82, (2.16, 5.97) (4.57, 8.02) (0.03, 0.14)

-271 -257 -268 -259

(-253,-290) (-237, -276) (-253, -285) (-234, -298)

Acroohasek (95% CI])

=Systolicblood pressure; bdiastolicblood pressure; °heartrate; %alivaryflow rate; percentage rhythm, proportion of variance accountedfor, on the average, by the fitted model; ~P-valuefrom zero-amplitudetest; gMidline-EstimatingStatistic Of Rhythm, a rhythm-adjustedmean;hstandarderror; ~measureof extenl of predictable change within a cycle; J95% confidenceinterval; kmeasureof timing of overall high values recurring in each cycle, expressed in (negative) degrees, with 360 equatedto period lengthand 0=0: 00.

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circadian stage. Thus, the results showed i n c o n s i s t e n c y a m o n g p a r t i c i p a n t s a n d / o r a m o n g c i r c a d i a n stages.

5. Discussion and conclusion In hindsight, it is clear that the study could have been improved upon. The failure to show an effect of U L F exposure on physiology and psychology might be due partly to the directional properties of the artificial magnetic field used, which may not have replicated sufficiently well the

natural magnetic pulsations. The orientation of the artificial magnetic field was horizontal, while the geomagnetic field in the area where the study was conducted was almost vertical to the ground. Another reason could be that the study used alternative current (AC) magnetic field unlike the natural magnetic field, which is in direct current (DC). Although the frequency of the artificial U L F waves was very low (0.0016 Hz) and the magnetic field was almost in DC, this difference might have contributed to the results. Other possible reasons for the negative results are that the intensity (50 nT) and/or the duration (8 hours) of the exposure were

G. Mitsutake et al. / Biomedicine & Pharmacotherapy 58 (2004) $20-$27

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Fable 2 Population-mean cosinor summary of mood, vigor, and estimated time intervals Variable Real Exposure pA" Nab CI-Ie SEd BMe Mf Vg SSSh TE i RTj Sham Exposure pAa Nab Ct( SEa BMe Mf

Vg SSSh TE~ RTj

PR" (%)

P~

ME.8ORTM 4- SEn ..Amplitude ° (95% Acrophase q (95% CIP)

56.4 48.8 50.2 51.3 49.9 55.9 53.8 58.1 11.7 50.2

0.002 0.847 0.083 0.326 0.101 0.009 0.004 <0.001 0.074 0.359

26.95 :~ 1.53 t4.92 4- 1.12 12.31 4- 0.88 14.13 4- 0.96 10.46 4- 1.06 3.7834- 0.24 3.3 4- 0.35 3.294 4- 0.32 59.2134-1.52 754.459± 15.18

2.89 (1.53, 4.25) 0.42 (0, 0) 1.26 (0, 0) 0.84 (0, 0) 0.71 (0, 0) 0.91 (0.36 1.45) 0.91 (0.44, 1.38) 0.96 (0.60, 1.33) 1.07 (0, 0) 5.47 (0, 0)

-260 (-226, -229) -23 (0, 0) -243 (0, 0) -214 (0, 0) -93 (0, 0) -248 (-229, -278) -248 (-223, -277) -67 (-39, -98) -104 (0, 0) -86 (0, 0)

45.0 41.9 47.2 38.2 48.5 51.0 39.5 39.9 8.7 38.2

0.015 0.970 0.081 0.071 0.369 0.079 0.006 0.001 0.495 0.485

26.41-4-1.86 13.984- 1.27 12.48 4- 0.70 13.57 4- 0.85 10.044-1.44 3.7184-0.42 3.324-0.50 3.275±0.40 58.2894-1.31 755.222z~14.91

2.13 (0.70, 3.56) 0.08 (0, 0) 0.97 (0, 0) 0.92 (0, 0) 0.30 (0, 0) 0.64 (0, 0) 0.69 (0.21, 1.17) 0.79 (0.35, 1.23) 0.46 (0, 0) 5.67 (0, 0)

-298 (-258, -359) -131 (0, 0) -268 (0, 0) -238 (0, 0) -165 (0, 0) -276 (0, 0) -284 (-267, -330) -84 (-67, -I I9) -210 (0, 0) -59 (0, 0)

aPositive affect; bnegative affect; °cheerfulness; dseriousness; ~bad mood; ~mood (on Mood and Vigor Scale); gvigor; ~'objective alertness (on Stanford Sleepiness Scale); ~estimated time intervals of 60 seconds; Jreaction time; kpercentage rhythm, proportion of variance accounted for, on the average, by the fitted model; 1P-value from zero-amplitude test; ~nMidline-Estimating Statistic Of Rhythm, a rhythm-adjusted mean; nstandard error; omeasure of extent of predictable change within a cycle; p95% confidence interval; qmeasure of timing of overall high values recurring in each cycle, expressed in (negative) degrees, with 360 equated to period length and 0=0: 00. Table 3 Overall mean differences in heart rate variability parameters between real and sham exposure

Real Exposure Mean N 69.75 5 NN b 898.97 5 SDNN c 72.15 5 ULFd 64.85 5 LF e 38.62 5 HF f 28.46 5 LF/HFg 1.50 5 Variab HR"

SD 3.63 30.99 11.85 6.60 6.14 6.78 0.21

Sham Mean 68.07 916.27 76.16 72.4l 41.16 30.72 1.49

Exposure N SD 5 6.54 5 60.08 5 10.80 5 7.17 5 7.91 5 8.12 5 0.22

t 0.65 -0.6 -0.9 -1.5 -0.9 -1 0.47

t-test df 4 4 4 4 4 4 4

P N.S. N.S. N.S. N.S. N.S. N.S. N.S.

NS: non-significant. "Heart rate. bNN intervals, cStandard deviations of NN intervals, dURra-low frequency spectral component (msec2). eLow frequency spectral component (msec2). n i g h frequency spectral component (msec2). gThe ratio of LF to HF.

i n a p p r o p r i a t e . S i n c e the p a r t i c i p a n t s w e r e s i n g l e - b l i n d e d to the c o n d i t i o n s o f the e x p e r i m e n t s , the p o s s i b i l i t y that t h e y g u e s s e d w h e t h e r t h e y w e r e e x p o s e d to t h e r e a l or s h a m m a g n e t i c f i e l d c a n n o t b e e x c l u d e d . T h e d i s c r e p a n c y in the r e s u l t s (i.e. H R V , b l o o d p r e s s u r e , m o o d , e s t i m a t e d t i m e intervals of 60 seconds, reaction time, and flow rate) b e t w e e n the p a r t i c i p a n t s m a y b e d u e to the d i f f e r e n c e in t h e s a m p l i n g rate. W h i l e , for e x a m p l e , h e a r t rate w a s m e a s u r e d w i t h a s a m p l i n g rate o f 273 H z for 24 h o u r s p e r m o n i t o r i n g session, mood was estimated every 4 hours while awake, giving a maximum of only five readings per session, and

thus less statistical p o w e r to detect a n y d i f f e r e n c e b e t w e e n r e s p o n s e s to real a n d s h a m e x p o s u r e . O n t h e p o s i t i v e side, a c i r c a d i a n r h y t h m w i t h a s i m i l a r t i m i n g was f o u n d for p o s i t i v e affect a n d c h e e r f u l n e s s , w h i c h both emphasized 'good humor'. Also validating earlier results w a s the failure to d e m o n s t r a t e a c i r c a d i a n v a r i a t i o n for n e g a t i v e affect, c o n f i r m i n g the f i n d i n g s o f Clark, W a t son, a n d L e e k a [7]. D a w e s ' f i n d i n g s o f c i r c a d i a n r h y t h m i c i t y in s a l i v a r y f l o w rate [8] w e r e also c o n f i r m e d . T h e results o f the further analysis of the HRV data suggest a possibility t h a t e a r l y n i g h t e x p o s u r e to t h e U L F m a g n e t i c f i e l d m a y

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Table 4 Population-mean cosinor summary of mood, vigor, and estimated time intervals

Variable SBPa MESOR" Amplitudep Acrophaseq DBP b MESOR Amplitude Acrophase HRc MESOR Amplitude Acrophase pA a MESOR Amplitude Acrophase Na ~ MESOR Amplitude Acrophase CH f MESOR Amplitude Acrophase SE g MESOR Amplitude Acrophase BM ~ MESOR Amplitude Acrophase Mi MESOR Amplitude Acrophase Vi MESOR Amplitude Acrophase SSS k MESOR Amplitude Acrophase R@ MESOR Amplitude Aerophase TEm MESOR Amplitude Acrophase F R n MESOR Amplitude Aerophase . . . .

Mean

Real Exposure N SD

73.10 4.62 -245.17 73.10 4.62 -245.17 62.56 7.42 -274.83 26.67 5.32 -241.30 14.74 2.79 -151.30 12.24 2.34 -245.00 14.15 2.42 -183.73 10.38 1.64 -87.91 10.38 1.04 -198.67 3.36 1.37 -214.50 3.44 1.51 -100.40 763.75 18.53 -136.30 58.77 2.14 -153.45 0,24 0.12 -256.00

12 12 12 12 12 12 t2 12 12 11 11 10 l1 11 10 ll 11 11 I1 I1 11 11 11 1l 9 9 9 I0 10 10 10 10 10 10 10 10 II 1l 11 15 15 15

5.91 2.33 50.54 5.91 2.33 50.54 4.34 2.83 25.08 3.24 2.10 79.92 2.16 t.55 114.84 1.95 1,76 66. I 0 1.98 1.31 100.23 2.19 0.59 64.67 0.61 0.79 90.73 0.84 0.60 1 t3.90 0,77 0.66 55,19 31,63 t3.30 89.77 3,21 1.20 7t.17 0,08 0.06 35.26

Sham Exposure Mean N SD 72.05 4. l 5 -219.50 72,05 4,15 -219.50 60.83 6.34 -276.83 27.41 4.70 -209,70 14.35 1.59 -219.00 12.74 2.64 -200.73 13.50 1.68 -234.73 9.94 1.63 -164.91 9.94 1.20 -216.33 3.45 1.10 -251,70 3.05 1,15 -101.90 685.81 16.53 -134.90 57.69 2,04 ~183,91 0,29 0,13 -264,13

12 t2 i2 12 12 12 12 12 12 11 I1 10 11 11 10 11 11 11 11 11 t1 11 11 11 9 9 9 t0 i0 10 10 10 10 i0 10 10 11 11 11 t5 15 15

5.33 1.80 81.94 5.33 1.80 81.94 4.42 2.93 34.16 3.48 3.03 123.98 2.59 0.93 108.92 1.29 1.73 118.36 1,72 0.80 71.26 2.95 0.93 78.61 0.95 0.72 95.48 1.02 0.76 91.69 0.62 0.57 62.35 242,53 14.65 93.66 2,61 1.29 87.36 0.09 0.06 37.91

t 1,02 0,59 -0.74 1,02 0.59 -0.74 1.26 0.88 0.19 -0.42 0,56 -0.60 0.36 1.97 1.66 -0,73 -0,35 -0,96 0,79 1,37 1,39 0,41 0.01 2.11 0.27 -0.71 0.67 -0.25 1.20 0.67 1,14 1.23 0.10 0,96 0.31 -0.03 1.51 0.28 0.98 -1.74 -0.51 0,62

t-test df 11 11 11 11 11 11 I1 II I1 10 10 9 10 10 9 t0 i0 10 10 10 10 10 10 10 8 8 8 9 9 9 9 9 9 9 9 9 10 10 10 15 15 15

P N.S. N.S, N.S. N.S. N.S. N.S. N.S. N.S. N.S. N.S. N,S. N.S. N.S. N.S. N.S. N.S. N.S. N.S. N.S. N.S. N.S. N.S. )k~S. N.S. N.S. N.S. hrs. N.S. N.S. NIS. N.S. N.S. N.S. N.S. N.S. N.S. N,S. N.S. N.S. N.S. N.5'. N.S.

NS: non-significant, aSystolic blood pressure, bDiastolic blood pressure. °Heart rate. ~Positive affect. ~Negative affect, fCheerfulness, gSeriousness. UBad mood. ~Moodrated on Mood and Vigor Scale. JVigor rated on Mood and Vigor Scale. kObjective alertness rated on Stanford Sleepiness Scale. ~Reactiontime. mEstimated time intervals of 60 seconds. ~Salivary flow rate. °Midline-Estimating Statistic Of Rhythm, a rhythm-adjusted mean. PMeasure of extent of predictable change within a cycle, qMeasure of timing of overalI high values recurring in each cycle, expressed in (negative) degrees, with 360 equated to period length and 0 =0: 00.

increase heart rate and r e d u c e heart rate variability o f those w h o are s u s c e p t i b l e to it. H o w e v e r , t h e y are i n c o n s i s t e n t a m o n g subjects and a m o n g circadian stages.

Futures studies w o u l d need to use m o r e rigorous designs, a larger sample size, artificial m a g n e t i c field o f appropriate strength and w a v e f o r m , and a better m a g n e t i c a l l y shielded

G. Mitsutake et al. / Biomedicine & Pharmacotherapy 58 (2004) $20-$27

[5] II ---- I~ m Ib

Participani:A Participant-B, Participant-A, Participant*B,

Reaie~;suie: 2ii00 ~,5;00 on JUL 7, 2 0 0 i Real exposure, 21:00 - 5:00 on JUL 7, 2001 Sharnexposure, 21:10-5:10onJUL21,2001 Sham exposure, 21:10-5:10onJUL21 2001

[6] 0

.................................................

©-fO

[7]

~-,

[8]

O-(

[9] 1

2

3

4 5 6 Sampling Interval

7

8

9

Fig. 5. Power-low slope of HRV for a monitoring session in which the participants were exposed to the real/sham magnetic field between 21:00 and 5:00. Sampling intervals 1 to 9 stand for a one-hour interval preceding the exposure, followed by one-, two-, two-, and three-hour during exposure, one-, two-, six-, and seven-hour of post exposure.

[10] [11]

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room with more space and that is shielded against not only ELF and VLF waves but also ULF waves, including the geomagnetic field.

[ 13]

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6. Acknowledgments We would like to thank Rob Menzies, University of Manitoba, for preparing the Helmholtz coils and all other electronic devices for the experiment and Colin Dawes for providing the equipment for saliva sampling. We would also like to thank James Burch, Colorado State University, for his useful advice on ELF magnetic field measurement. We also wish to thank the Canadian Space Agency, which constructed, maintained and operated the CANOPUS instrument array, for providing us with the data used in this study. Lastly, we thank the participants for their time and contribution to this study.

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$27

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