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Relationship between human physiological parameters
and geomagnetic variations of solar origin
S. Dimitrova
*
Solar Terrestrial Influences Laboratory, Bulgarian Academy of Sciences, Acad. G. Bonchev Str. Bl. 3, Sofia 1113, Bulgaria
Received 29 August 2004; received in revised form 7 March 2005; accepted 23 March 2005
Abstract
Results presented concern influence of increased geomagnetic activity on some human physiological parameters. The blood pres-
sure and heart rate of 86 volunteers were measured on working days in autumn 2001 (01/10–09/11) and in spring 2002 (08/04–28/05).
These periods were chosen because of maximal expected geomagnetic activity. Altogether 2799 recordings were obtained and ana-
lysed. Questionnaire information about subjective psycho-physiological complaints was also gathered. MANOVA was employed to
check the significance of the influence of three factors on the physiological parameters under consideration. The factors were the
following: (1) planetary geomagnetic activity level estimated by Ap-index and divided into five levels; (2) gender – males and females;
(3) blood pressure degree – persons in the group examined were divided into hypotensive, normotensive and hypertensive. Post hoc
analysis was performed to elicit the significance of differences in the factorsÕlevels. The average arterial blood pressure of the group
was found to increase significantly with the increase of geomagnetic activity level. The average increment of systolic and diastolic
blood pressure of the group examined reached 9%. This effect was present irrespectively of gender. Results obtained suppose that
hypertensive persons have the highest sensitivity and the hypotensive persons have the lowest sensitivity of the arterial blood pres-
sure to increase of geomagnetic activity. The results did not show significant changes in the heart rate. The percentage of the persons
who reported subjective psycho-physiological complaints was also found to increase significantly with the geomagnetic activity
increase and the highest sensitivity was revealed for the hypertensive females.
Ó2005 COSPAR. Published by Elsevier Ltd. All rights reserved.
Keywords: Geomagnetic activity; Arterial blood pressure; Human physiological state
1. Introduction
Human physiological status is influenced by environ-
mental factors changes requiring from the organism and
its vegetative nervous system a large range of adaptation
reactions, which are decreased in case of different dis-
eases. Although of the skepticism about the investiga-
tions of the relationship between geomagnetic field
(GMF) variations of solar origin and human beings
there are publications during the last two decades which
disclose influence of helio-geophysical factors on biolog-
ical processes. It has been revealed that cardio-vascular,
circulatory, nervous and other functional systems react
under changes of geophysical factors (Cornelissen
et al., 2002; GurfinkelÕet al., 1995; Kay, 1994; Persinger
and Richards, 1995; Watanabe et al., 1994; Zhadin,
2001). In most of the cases the reactions observed are
adaptive and support an easier endure of the changes
ensuring survival of the biological system in the changed
environment. But in some cases there is no such protec-
tive reaction or it is prevented. Then the organism is ex-
posed to a danger by the influence of the environment
factors changes of any kind. The presence of this reac-
tion is especially important for the sick and unstable
0273-1177/$30 Ó2005 COSPAR. Published by Elsevier Ltd. All rights reserved.
doi:10.1016/j.asr.2005.03.153
*
Tel.: +359 2 979 22 18.
E-mail address: svetla_stil@abv.bg.
www.elsevier.com/locate/asr
Advances in Space Research 37 (2006) 1251–1257
subjects (emotionally and physiologically unstable,
physically overloaded, exhausted and under stress
persons).
Changes in the GMF are an indirect indicator for the
geoeffective solar events. During the last years we have
studied the influence of changes in geomagnetic activity
(GMA) by using different indices (Dst-, Ap-, Kp-indices
and amplitude of H-component of the local GMF) on
human physiological and psycho-physiological parame-
ters. The results obtained from the investigations of
influence of changes in Ap-index on the arterial blood
pressure (ABP), pulse pressure (PP), heart rate (HR)
and subjective psycho-physiological complaints (SPPC)
are presented here.
2. Materials and methods
Data were obtained in 86 volunteers (33 males and 53
females) of an average age 47.8 (±11.9) years. They were
persons working at different Institutes of the Bulgarian
Academy of Sciences in Sofia city (latitude: 42°43 0
North, longitude: 23°200East). There were 16 hypoten-
sive, 41 normotensive and 29 hypertensive persons in the
group examined. The recording of the physiological
parameters was performed from 01/10/2001 to 09/11/
2001 and from 08/04/2002 to 28/05/2002. These periods
were chosen because of the high probability for geo-
effective solar storms during autumn and spring. Addi-
tionally, these years were of maximal solar activity.
Systolic and diastolic blood pressure (SBP and DBP)
and HR were measured. PP (algebraic difference be-
tween SBP and DBP) was calculated. ABP was regis-
tered by sphygmomanometric method to the single
mmHg and HR by palpatoric method on the arteria
radialis as beats/min and by counting for a full minute.
Questionnaire information about SPPC was obtained as
well. One and the same person performed the measure-
ments at an appointed time for each volunteer on every
workday. The volunteers and the person who performed
the measurements were blinded to the degree of GMA.
Some of the persons examined could not be found daily
at the appointed time and then they were left out of data
for the relevant day. If the persons examined reported
some personal troubles and, respectively, their physio-
logical parameters were changed as a result, their mea-
surements were not considered. Altogether 2799
registrations for each of the physiological parameters
under consideration were gathered.
The questionnaire data concerned information about
general condition, working ability, sleep disturbances,
nausea, vertigo, headache, stitches or aches in the heart
area, heart thumping, tachycardia, arrhythmia and
other information about physiological or psychological
discomfort of the persons examined. If there was a psy-
cho-physiological complaint during a particular day by
a person, then this person was classified into the group
with ‘‘complaints’’ and marked by ‘‘1’’ for the corre-
sponding day. Persons with no psycho-physiological
complaints for the corresponding day were classified
into the group ‘‘there are no complaints’’ and marked
by ‘‘0’’.
A multiple analysis of variance (MANOVA) for the
following three factors: GMA, gender and blood pres-
sure degree was performed. The influence of these fac-
tors on SBP, DBP, PP, HR and SPPC was investigated.
According to variations of daily planetary Ap-index
the factor ‘‘GMA’’ was divided into five levels: first level
(calm GMA)– Ap-index was lower than 15; second level
(weak storm) – Ap-index was in the range 15–30; third
level (moderate storm) – Ap-index was in the range 30–
50; fourth level (major storm) – Ap-index was in the
range 50–100; fifth level (severe storm) – Ap-index was
larger than 100. Fig. 1 shows variations of Ap-index
during both periods of registrations. The data about
planetary GMA were got from Internet (World Data
Center for Geomagnetism, Kyoto).
The factor ‘‘gender’’ was regarded as a two level fac-
tor: males and females.
The factor ‘‘blood pressure degree’’ was divided into
three levels: hypotensive, normotensive and hyperten-
sive persons.
The purpose of ANOVA is to test for significant dif-
ferences between means by comparing variances. In AN-
OVA a null hypothesis is under consideration, according
to which the treated factor A does not effect significantly
variation of the parameter X. This means when compar-
ing the mean values of Xat each factor A level there is
no statistically significant difference between them. If
such a difference found, then the null hypothesis should
be rejected. MANOVA is more powerful and flexible
method in comparison to the StudentÕst-test. By MAN-
OVA we can check the influence of each factor taking
into consideration the influence of the other factors as
well as we can establish the interaction effect for the
factors.
Date
Ap
0
10
20
30
40
50
60
70
80
90
100
110
120
01.10.01
10.10.01
20.10.01
30.10.01
08.04.02
17.04.02
27.04.02
07.05.02
17.05.02
27.05.02
Fig. 1. Ap-index variations during examination periods.
1252 S. Dimitrova / Advances in Space Research 37 (2006) 1251–1257
A post hoc analysis (Neman–Keuls test) was also
used to establish the statistical significance of the differ-
ences between the average values of the measured phys-
iological parameters in the separate factor levels.
MANOVA method was employed using the package
for statistical analyses STATISTICA. From MANOVA
variants (repeated measures and between-groups facto-
rial design) the between-groups factorial design was cho-
sen because: during the parameters measurements
always some of the persons examined (up to 20–25%)
were absent or reported some subjective troubles; the
experiment could not be planned with respect to the
environmental conditions; the persons examined were
divided into groups (males and females; hypo-, normo-
and hypertensive persons). Therefore the samples exam-
ined were regarded as independent and the repeated
measures variant was not used.
The chosen level for statistical significance was
p< 0.05.
3. Results
Three-factor analysis of variance was employed and
the main effect and the interaction effect for the factors
under consideration on the physiological parameters
examined were investigated. Table 1 presents the signif-
icance levels (pvalues).
3.1. Arterial BP
The main effect for the factor Ap-index on SBP and
DBP is statistically significant (Table 1). The average va-
lue of ABP of the group increased with the increment of
GMA (Fig. 2). Vertical bars in the figure denote 0.95
confidence intervals (CI). The sharpest increase of
ABP was during severe geomagnetic storms. Post hoc
analysis revealed that the average value of the group
for SBP and DBP were significantly higher during severe
geomagnetic storms in comparison to all of the other
GMA levels. It was also obtained that DBP increased
significantly still at major geomagnetic storms in com-
parison to calm GMA. The maximal range of changes
for SBP is 8.7% and for DBP 8.6%. These results reveal
that an adverse affect on ABP of the group examined
render severe geomagnetic storms and on DBP still ma-
jor geomagnetic storms.
The main effect for the factor gender revealed that in
principle males have significantly higher ABP in com-
parison to females. The main effect for the factor blood
pressure degree revealed significantly lowest value of
ABP for hypotensive persons and significantly highest
value of ABP for hypertensive persons.
The results obtained from the two-factor interaction
effect for the factors Ap-index and gender did not reveal
a difference in the ABP reaction of males and females
(Table 1). The range of increase of SBP and DBP from
1st to 5th GMA level for the both genders was very sim-
ilar (for females, respectively, 8.6% and 7.8% and for
males 8.8% and 9.7%). Post hoc analysis showed that
malesÕSBP and DBP during severe geomagnetic storms
were significantly higher than the other GMA levels. It
was obtained for femalesÕSBP significant increase at
5th level in comparison to 1st, 2nd and 3rd GMA level
and for DBP significant increase at 5th level in compar-
ison to 1st GMA level. The results obtained indicate an
adverse affect for severe geomagnetic storms on the ABP
irrespectively of gender.
The two-factor interaction effect for the factors Ap-
index and blood pressure degree on SBP and DBP did
Table 1
Significance levels (p-values) of the main effect and interaction effect for the factors investigated (GMA; Gender; Blood pressure degree) on the
physiological parameters examined
Effect (main and interaction effect for the factors) p
SBP DBP PP HR SPPC
Ap-index 0.000* 0.000* 0.296 0.553 0.000*
Gender 0.000* 0.000* 0.000* 0.000* 0.000*
Blood pressure degree 0.000* 0.000* 0.000* 0.000* 0.010*
Gender*Blood pressure degree 0.265 0.818 0.069 0.195 0.053
Ap-index*Gender 0.869 0.905 0.869 0.766 0.010*
Ap-index*Blood pressure degree 0.209 0.657 0.287 0.923 0.005*
Ap-index*Gender*Blood pressure degree 0.976 0.994 0.935 0.965 0.002*
S
y
st(L) Diast(R)
12345
Ap-index levels
100
105
110
115
120
125
130
Systolic BP, mmHg
75
80
85
90
95
100
Diastolic BP, mmH
g
Fig. 2. Main effect for the factor Ap-index on SBP and DBP (±95%
CI).
S. Dimitrova / Advances in Space Research 37 (2006) 1251–1257 1253
not reveal significant differences in the reaction of ABP
of hypotensive, normotensive and hypertensive persons
to GMF changes (Table 1). Although hypertensive per-
sons had the largest range of increase of SBP (14.4%)
and DBP (11.4%) and hypotensive persons had the low-
est range of increase of SBP (3.2%) and DBP (4.1%)
from 1st to 5th GMA level. The increment for normo-
tensives was, respectively, 6.9% and 9.6%. Post hoc anal-
ysis revealed that SBP and DBP for hypertensive
persons increased significantly during severe storms in
comparison with all of the other GMA levels and
DBP of normotensive persons increased significantly
during severe geomagnetic storms in comparison to
1st, 2nd and 3rd GMA level. These results show that se-
vere geomagnetic storms have adverse affect on ABP of
hypertensive persons and on DBP of normotensive
persons.
The effect of the three-factor interaction did not show
significant differences (Table 1) in the ABP of the six
subgroups examined (males/females/hypotensive/nor-
motensive/hypertensive). Post hoc analysis employed re-
vealed that significant changes occurred during severe
geomagnetic storms in SBP of hypertensive persons
(both males and females) and in DBP of hypertensive
males. These results can be noticed in Figs. 3 and 4
and also indicate a higher sensitivity for ABP of hyper-
tensive persons in respect to changes in Ap-index.
3.2. Pulse pressure
The main effect for Ap-index did not reveal statisti-
cally significant influence on PP (Table 1). Fig. 5 shows
that PP increased sharply during severe geomagnetic
storms and the maximal range of changes was 8.7%.
Post hoc analysis confirmed that PP of the group during
severe geomagnetic storms was significantly higher than
PP for the other GMA levels.
The influence of the interaction effect for the factors
Ap-index and gender on PP did not reveal significant
differences in the PP reaction of males and females
(Table 1). It was obtained that the only considerable
increase of PP for both genders was during severe
storms (for males 8.2% and for females 11.6%) but it
was not disclosed by Post hoc analysis statistically sig-
nificant increment of PP during severe geomagnetic
storms compared to the other GMA levels neither for
males nor for females.
The interaction effect for Ap-index and blood pres-
sure degree did not reveal significant changes (Table 1)
in PP reaction of hypo-, normo- and hypertensive per-
sons to GMA changes. Although, the results obtained
from additional analysis performed suppose that hyper-
tensive persons have the most sensitive PP to GMA
changes. It was determined that the maximal increase
of PP for hypotensive persons was 6.1%, for normoten-
sive persons only 2.6% and for hypertensive persons
21.2%. Post hoc analysis revealed that only hypertensive
persons increased statistically significantly PP during se-
vere geomagnetic storms compared to all of the other
GMA levels.
Hypo Normo Hyper
Males
12345
Ap-index levels
80
90
100
110
120
130
140
150
160
170
Systolic BP, mmHg
Females
12345
Ap-index levels
Fig. 3. Interaction effect for the factors Ap-index, gender and blood
pressure degree on SBP (±95% CI).
Fig. 4. Interaction effect for the factors Ap-index, gender and blood
pressure degree on DBP (±95% CI).
PP(L) HR(R)
12345
Ap-index levels
35
40
45
50
Pulse pressure, mmHg
55
60
65
70
75
80
Heart rate, beats/min
Fig. 5. Main effect for the factor Ap-index on PP and HR (±95% CI).
1254 S. Dimitrova / Advances in Space Research 37 (2006) 1251–1257
The influence of the interaction effect for the three
factors investigated is not significant (Table 1) but the
most considerable increment of PP was obtained for
hypertensive persons (both males (21.2%) and females
(21.5%)). Post hoc analysis performed revealed signifi-
cant increase of the hypertensive males PP during severe
geomagnetic storms compared to 1st and 3rd GMA le-
vel. This result indicates that probably PP of hyperten-
sive males is the most sensitive to GMF variations of
solar origin.
3.3. Heart rate
The main effect for Ap-index on HR revealed that the
average value of HR of the group examined increased
with the increment of GMA but this increase reached
only 1.8% and is not statistically significant (Table 1,
Fig. 5). It was not revealed statistically significant differ-
ence in the HR reaction of the subgroups examined to
Ap-index changes (Table 1).
3.4. Subjective psycho-physiological complaints
The main effect for GMA on SPPC is statistically sig-
nificant (Table 1). It is seen in Fig. 6 that SPPC in-
creased during moderate and especially during severe
geomagnetic storms. It was established by post hoc anal-
ysis that the percentage of the persons in the group with
SPPC at 5th GMA level was significantly higher than at
1st, 2nd and 4th GMA level as well as at 3rd level than
at 1st GMA level. The increment from 1st to 5th level
was 18.9% and during severe geomagnetic storms 1/3
of the persons examined reported complaints. The re-
sults obtained show that the most adverse influence on
the group examined render moderate and severe geo-
magnetic storms.
The main effect for the factor gender revealed that in
principle the percentage of females in the group with
SPPC is significantly higher than the percentage of
males with SPPC. The main effect for the factor blood
pressure degree revealed that with the increase of the
blood pressure degree the percentage of SPPC rises sig-
nificantly. Post hoc analysis showed that the percentage
of the hypertensive persons who reported SPPC is signif-
icantly higher than the percentage of the hypotensive
persons who reported SPPC.
The influence of the interaction effect for the factors
Ap-index and gender on SPPC revealed significant dif-
ferences in SPPC reaction of males and females (Table
1). Fig. 7 shows that females have more sensitive psy-
cho-physiology than males to the increase of GMA.
The percentage of females with SPPC increased more
considerably with the increment of Ap-index and during
severe storms nearly a half of the females in the group
examined reported SPPC. Post hoc analysis revealed
that only females increased significantly SPPC during se-
vere geomagnetic storms compared to all of the other
levels.
The interaction effect for the factors Ap-index and
blood pressure degree on SPPC revealed significant dif-
ferences in the reaction of the three subgroups examined
(Table 1). It is seen in Fig. 8 that the sensitivity of the
persons to the increase of GMA rises with the increase
of the blood pressure degree. Hypertensive persons
12345
A
p
-index levels
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
Subj. phys. complaints, %
Fig. 6. Main effect for the factor Ap-index on SPPC (±95% CI).
Males Females
12345
Ap-index levels
-0.1
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Subj. phys. complaints, %
Fig. 7. Interaction effect for the factors Ap-index and gender on SPPC
(±95% CI).
Fig. 8. Interaction effect for the factors Ap-index and blood pressure
degree on SPPC (±95% CI).
S. Dimitrova / Advances in Space Research 37 (2006) 1251–1257 1255
had the biggest range of changes of the percentage of
persons with SPPC – during severe storms 41.3% from
the hypertensive subjects reported complaints. For the
normotensive persons the percentage of the subjects
with SPPC increased considerably during moderate
and severe geomagnetic storms when 1/3 of them re-
ported SPPC. The percentage of hypotensive subjects
with SPPC increased during weak and major storms
and reached 22.1%. It was obtained by post hoc analysis
that only hypertensive persons significantly increased
SPPC during severe storms in comparison to 1st and
4th GMA level. These results show that severe storms
render significant adverse effect on hypertensive persons
and suggest that hypertensive persons have the most
sensitive psycho-physiological reaction to GMF
variations.
It was also obtained significant influence for the three-
factor interaction on SPPC (Table 1). It is seen in Fig. 9
that the largest increase of SPPC was for the hyper- and
normotensive females during severe geomagnetic storms
as well as for the hypotensive males during major storms.
The range of changes of the percentage normotensive
males with complaints was the smallest. Post hoc analysis
revealed only for hypertensive females a significant in-
crease during severe storms in comparison to 1st, 2nd
and 4th GMA level, i.e., there is a significant adverse ef-
fect during severe planetary geomagnetic storms on the
psycho-physiological status of the hypertensive females.
4. Conclusions and discussion
ABP of the group examined increases with the incre-
ment of planetary GMA and the maximal increase is
about 9%. DBP increases significantly still at major
storms and SBP at severe storms. PP also increases sig-
nificantly during severe storms by 9%. In addition, the
percentage of the persons who reported SPPC increases
significantly during moderate and severe storms and in
the last case it covered 1/3 of the persons in the group
examined. It was not established a significant change
in HR under GMA variations. The biggest increase of
HR is only 1.8%.
The results obtained did not reveal significant differ-
ence in the reaction of ABP, PP and HR for the genders.
Both males and females increase significantly ABP dur-
ing severe geomagnetic storms. Regarding psycho-phys-
iological reaction it was obtained that females are more
sensitive – only they are influenced significantly by se-
vere geomagnetic storms and about a half of them re-
ported SPPC.
The analyses revealed that with the increase of the
blood pressure degree the sensibility of the persons to
GMA changes increases – it was not established a sensi-
tivity of the hypotensive personsÕABP to the increment
of GMA; normotensive persons increased significantly
only DBP during severe storms; and hypertensive per-
sons increased considerably and significantly both SBP
and DBP during severe geomagnetic storms. Addition-
ally, only for the hypertensive persons it was obtained
a significant increase of PP as well as of the percentage
of the subjects with SPPC during severe storms.
Post hoc analyses employed for the three-factor inter-
action effects also support the hypothesis that physiolog-
ical parameters of the hypertensive persons are more
sensitive to the changes in planetary GMA. Both males
and females hypertensive persons increase significantly
SBP during severe storms and hypertensive males in-
crease significantly DBP and PP under these conditions.
Regarding psycho-physiological reaction it concerns
hypertensive females – only their SPPC are affected sig-
nificantly by severe storms.
The influence of some meteorological elements (daily
average atmospheric pressure, air temperature and rela-
tive humidity; variation of the daily average atmospheric
pressure and temperature between two consecutive days;
and daily amplitude of the temperature) on the physio-
logical parameters examined was also investigated. Some
of the results obtained by ANOVA (not MANOVA) are
statistically significant but the changes of the physiolog-
ical parameters are not so biologically significant as they
are under GMA influence. The maximal range of
changes is: for ABP 2.1–8%, PP 2.3–6.8%, HR 1.8–
4.2%, SPPC 9–20.3%. The observation periods were dur-
ing spring and fall when the meteorological elements at
our latitudes are very similar and the weather is neither
hot nor freezing. We suppose that this is the reason not
to find a significant biological influence of the meteoro-
logical factors. Should we perform our examinations
for the all year interval possibly such influence would
be established. This fact is an advantage of the investiga-
tions performed since decreasing of the influence of mete-
orological factors helps to separate the prevailing
influence of the factor under consideration – GMA.
Another important advantage of this study is that the
measurements performed were every working day for a
Hypo Normo Hyper
Males
12345
Ap-index levels
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
Subj. phys. complaints, %
Females
12345
Ap-index levels
Fig. 9. Interaction effect for the factors Ap-index, gender and blood
pressure degree on SPPC (±95% CI).
1256 S. Dimitrova / Advances in Space Research 37 (2006) 1251–1257
long period of time but only within several months and
not years – a time, which supposes a lack or minimal
changes in the physiological parameters of the persons
examined.
The results obtained add further evidence to previous
similar but retrospective investigations (Ghione et al.,
1998; Stoupel et al., 1995) that blood pressure seems
to be affected by geomagnetic variations of solar origin.
It suggests that helio-geophysical forecasts are needed
for timely applying prophylactic measures (pharmaco-
logical and regime) to prevent the adverse physiological
reaction of the sensitive and unstable persons.
Acknowledgements
We thankfully acknowledge the contribution of all
volunteers who took part in the examinations.
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