The effects of slight atmospheric pressure fluctuations on the occurrence of emergency transport due to suicidal injuries

doi:10.4236/health.2010.25067

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Vol.2, No.5, 448-453 (2010)

doi:10.4236/health.2010.25067

Health

The effects of slight atmospheric pressure fluctuations

on the occurrence of emergency transport due to

suicidal injuries

Lyudmyla Aleksandrovna Didyk1*, Yuriy Pavlovich Gorgo2, Joris Jan Josef Dirckx3,

Irina Aleksandrovna Semenova4, Nataliya Petrovna Didyk1, Dmytro Sergeevich Gorlov5

1Institute of Physics, National Academy of Sciences of Ukraine, Kyiv, Ukraine; *Corresponding Author: [email protected]

2Inter-University Medical Engineering Department, National Technical University of Ukraine “Kyiv Polytechnic Institute”, Kyiv,

Ukraine; [email protected]

3Biomedical Physics, University of Antwerp, Antwerp, Belgium; [email protected]

4Department of Pediatric, Social and Forensic Psychiatry, National Medical Academy of Post-graduate Education named after P.L.

Shupyk, Kyiv, Ukraine; [email protected]

5Biological Department, Taras Shevchenko National University, Kyiv, Ukraine; [email protected]

Received 15 January 2010; revised 1 February 2010; accepted 3 February 2010.

ABSTRACT

The objective of this study was to test the hy-

pothesis that a relation exists between slight

atmospheric pressure fluctuations (APF) in the

far infrasound frequency range and daily num-

ber of emergency transport events due to sui-

cidal injuries (EESU). The regression models to

compare groups were used to assess the rela-

tion of EESU to the mean daily amplitude of

APF (APF-A) and to the ratio of APF amplitude

averaged over the daytime to the APF amplitude

averaged over the nighttime (Rdn). To eliminate

the confounding effects of basic meteorological

parameters and annual trend in EESU, the non-

parametric smoothing method was used in a

stepwise manner. The low APF-A (95% CI = 1.06-

1.16 Pa) compared to their common middle lev-

els and the high (95% CI = 3.18-3.64 Pa), as well

the low Rdn (СI = 0.83-0.92) and very high Rdn

(CI = 3.05-3.77) compared to their more closed

to common regular values (СI = 1.69-1.90) turned

out to be more beneficial factors promoting the

decrease in the incidence of EESU. We suppose

that more attention needs to be paid to the me-

teorotropic effects of APF on certain kinds of

psychopathology resulting in suicidal behaviour,

and further investigations in different geograph-

ical and climatic conditions, especially in those

with more intense atmospheric perturbations,

are necessary.

Keywords: Atmospheric Pressure Fluctuations;

Suicidal Injuries; Emergency Events

1. INTRODUCTION

The weather effects upon human mental state and be-

haviour have long been discussed in literature. There are

considerable numbers of evidences on the severe nega-

tive weather after-effects on people with psychical dis-

orders resulting in suicidal behaviour. The basic mete-

orological parameters (ambient temperature, humidity,

atmospheric pressure and wind velocity), as well the

certain physical weather condition (hours of sunlight,

cloud cover and precipitation) were suggested as the

external triggers for development of suicidal ideation

and action [1-7].

However, very little attention has been paid to possi-

ble effects of other atmospheric parameters on human

behaviour. It was suggested, that slight atmospheric

pressure fluctuations (APF) in the far infrasound fre-

quency range is important meteorotropic factor influenc-

ing on mental function and behaviour [8-10]. The APF

penetrate into buildings [11,12], therefore they could

influence on people indoors and, as well as outdoors.

Long ago Mezernitsky P.G. [13] pointed to the high

sensitivity of the central nervous system to atmospheric

pressure “micropulsations”. Vladymirsky B.M. [9] sug-

gested the psychotropic effects of natural atmospheric

infrasound. In line with these suggestions Green J.E. and

Dunn F. [8] reported the correlation between strong

naturally occurring infrasonics and selected kinds of

human behaviour.

The possible effects of natural APF on human mental

activity and autonomic indices, as well the symptoms of

central nervous systems and vestibular disorders were

confirmed by the experimental investigations with artifi-

cial pressure oscillations in the far infrasound frequency

L. A. Didyk et al. / HEALTH 2 (2010) 448-453

449

range [10,14].

Some authors believed that the increase in anxiety

levels in people with mental disorders or incidences of

suicides during episodes of strong wind could be at least

partly due to meteorotropic effects of APF created by

wind induced turbulence of airflows [10,15].

The objective of this study was to examine whether a

relation exists between natural APF and suicidal behaviour.

For this the daily number of emergency transport events

due to suicidal injuries (EESU) was related to mean

daily integral amplitude of APF (APF-A) in the far

infrasound frequency range and to the ratio of APF

integral amplitude averaged over the daytime to the APF

integral amplitude averaged over the nighttime (Rdn).

The study was performed in Kiev locality (Ukraine) with

moderate climatic condition, where calm and relatively

slight windy weather is prevailing.

2. MATERIALS AND METHODS

Daily numbers of emergency transport events on suicidal

injuries (EESU) for the period from 1 July 2005 to 30

June 2006 were obtained from Kyiv Station of emergency

services and medicine of catastrophes. During this time

the outdoor continuous measurements of atmospheric

pressure have been performed with a standard micro-

barometer. The value of atmospheric pressure was re-

corded every 0.5 s. A special computer program devel-

oped by us was used to calculate average integral ampli-

tudes of APF in the range of their periods from 3 s to

120 s over each 1 h of the day. The range of APF periods

was selected allowing for the results of previous inves-

tigations of biological effects of APF in the far infra-

sound frequency range [10,12].

The mean daily value of APF integral amplitude

(APF-A) and the ratio of APF integral amplitude averaged

over the daytime (from 8:00 to 20:00 hours) to APF in-

tegral amplitude averaged over the nighttime (from

20:00 to 8:00 hours) (Rdn) were used for the analysis

allowing for the results of previous investigations of

biological effects of APF in the far infrasound range of

their periods [12].

Three-hourly meteorological data were obtained from

Kyiv Geophysical Observatory for the same year period.

Mean daily temperature (T), relative humidity (RH) and

atmospheric pressure (AP) were considered as potential

confounding variables for the relation of EESU to

APF-A.

As APF are causally related to wind induced turbu-

lence, the possible interrelation between effects of APF-A

and wind velocity (WV) was examined.

The number of a day in the course of the year (Y) was

included in the model to control the effects of time-vary-

ing environmental factors on the year dynamics of EESU.

This variable has associations with annual changes in

length of daylight, weather parameters and social factors

influencing on suicidal rates.

The polynomial approximation was used to assess

visually the functional shape of yearly dynamics of

EESU, as well as EESU relations with APF-A and Rdn.

The regression models to compare groups [16] were

used to assess the relation of EESU to APF-A and Rdn.

If significant difference in EESU was revealed be-

tween two categories of the values of independent vari-

able the numbers of days in first and second categories

were defined by changing the boundary between them

until the most significant difference in EESU was ob-

tained.

The negative or positive effect of the one category of

values of independent variable versus the other category

was determined correspondingly as a percentage in-

crease or decrease in number of EESU.

To eliminate the effects of potential confounding

variables, the non-parametric smoothing method (Loess

technique) was used in a stepwise manner [17].

We controlled the day of the week effects by dummy

variables. All public holidays were excluded from the

data. A few days of EESU and atmospheric data were

lost. Hence 345 days were used for the analysis.

The number of EESU and values of atmospheric

parameters were not normally distributed. Therefore,

non-parametric (Mann-Whitney U-test and Spearman’s

rank correlation test) estimations were used. Matlab 6.5

(Curve Fitting Toolbox), Statistica 6 and MS Excel were

applied for statistical analysis.

3. RESULTS

3.1. Atmospheric Data

Table 1 provides data on APF-A and Rdn values. Maxi-

mal value for hourly amplitude of APF during the year

was 22.5 Pa.

We found high correlation between APF-A and WV (r =

0.72, p < 0.00001), though this correlation was signifi-

cantly reduced (r = 0.23, p = 0.04, n =77) in the range of

low WV values (< 1.5 m/s). Dependency of the correla-

tion coefficient on the value of WV was consistent with

the non-linear character of causal relationships between

APF and WV [18]. According to this character, at high

WV (above 2 m/s) the APF increased rapidly with in-

creasing WV, as the wind-induced effects dominated. At

lower WV value (less than 0.5-1.5 m/s) there was only a

moderate increase in the APF, as they were less dependent

on the wind.

3.2. EESU Data

The total number of EESU for 345 days was 1036.

The yearly dynamics of EESU revealed significant

seasonality (Figure 1). The significant season-specific

L. A. Didyk et al. / HEALTH 2 (2010) 448-453

450

Openly accessible at

Table 1. Data on daily values of APF and Rdn during the year.

95% CI Maximum Minimum

APF-A (Pa) 2.64-3.05 11.07 0.7

Rdn 1.43-1.62 7.2 0.21

187173 259 345

Day

EESU

Figure 1. Polynomial model of yearly dynamics (from 1 July

2005 to 30 June 2006) of the number of EESU.

difference in the number of EESU was found between

warm days (T, CI = 17.40-19.18) during summer-autu-

mn season (from 1 July to 5 October 2005 and from 2

June to 30 June 2006, n = 122) and the other colder days

(T, CI = 1.45-3.75) of the year (from 6 October 2005 to

1 June 2006, n = 223). The number of EESU proved to be

greater (CI = 3.01-3.72) during warm summer-autumn

period in comparison with the colder period of the year

(CI = 2.60-3.06, p = 0.01).

3.3. The Relation between EESU and APF-A

The APF-A did not reveal significant relation with EESU

when their raw data were considered (Figure 2). The

functional form of the relation between EESU and

APF-A was changed after adjustment for the Y and T

variables. Significant difference in EESU was found

only between two categories of APF-A values, which we

considered as low and middle-high (Table 2). The num-

ber of EESU turned out to be significantly less on days

with low APF-A than on days with middle-high APF-A.

The category of low APF-A included about one fourth of

all days of the year (n1 = 85). The other days (n2 = 260)

with middle and high APF-AI compiled the second

category.

Significant difference in the number of EESU be-

tween two categories of APF-A values, which was re-

vealed after adjustment for Y and T, pointed to interfere-

ing effects of these two confounding variables on the

relation between EESU and APF-A. It was mentioned

above that greater numbers of EESU were observed

during warm summer-autumn season compared to the

other colder time of the year. Even more pronounced

difference in EESU was found between two categories

of T values. The number of EESU was significantly

2.0

3.0

4.0

187173 259345

Day sorted by APF-A value

EESU

Figure 2. The number of EESU plotted against the day sorted

by APF-A value in ascending order. Polynomial model: thin

line (0)—raw data, thick line (5)—data adjusted for the four

potential confounding variables (Y, T, AP, RH) and Rdn.

Table 2. 95% Confidence intervals for two categories of

APF-A (low and middle-high) and corresponding number of

EESU for data adjusted for two variables—Y and T (EESU/2)

and five variables—Y, T, AP, RH and Rdn (EESU/5).

Low APF-A

95% CI

n1 = 85

Middle-high APF-A

95% CI

n2 = 260

Va lu e

APF-A

(Pa) 1.06-1.16 3.18-3.64

EESU/22.34-3.03 2.90-3.31 0.046

EESU/52.25-2.90 2.95-3.29 0.0034

Note: p - significance of the difference in the number of EESU be-

tween two categories of APF-A values.

greater (p < 0.002) on days with high T (17.15С (CI =

15.97-18.32), n2 = 128) compared to days with low T

(2.8С (CI = 1.66-4.03С), n = 217). The ranges of T

values on days with low and middle-high APF-A turned

out to be significantly different also. The value of T was

almost two times higher (13.35С (CI = 11.23-15.46))

on days with low APF-A compared to days with middle-

high APF-A (6.39С (CI = 5.11-7.66)). Therefore, the

decrease in number of EESU on days with low APF-A,

which prevailed during warm season, could be interfered

by simultaneous effects of the comfort warm T promot-

ing an increase in number of EESU.

The difference in number of EESU between two

categories of APF-A values remained significant after

following stepwise adjustment for the AP and RH vari-

ables (p = 0.02). After additional adjustment for the Rdn

the significant difference in EESU between low and

middle-high APF-A became more pronounced (p =

0.0034, Table 2). The percentage decrease in the number

of EESU on days with low APF-A versus the mid-

dle-high APF-A was –17.6% (–23.7 - –11.8).

This difference was also significant after additional

adjustment for WV (after adjustment for the four con-

founding variables and WV p = 0.033) that suggested the

L. A. Didyk et al. / HEALTH 2 (2010) 448-453

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independent on WV effects of APF-A on EESU.

3.4. The Relation between EESU and Rdn

Figure 3 shows the functional shape of plots of EESU

(raw data and data adjusted for the four variables and

APF-A) vs the day sorted by Rdn value in ascending

order. This shape suggested the three categorical model

of the relation between EESU and Rdn. After adjustment

for the four variables and APF-A significantly greater

number of EESU proved to be at days with Rdn mid-

dle-high (n2 = 161) values comparing to days with Rdn

low (n1 = 150) or very high (n3 = 34) values (Table 3).

This classification of Rdn values was used taking into

consideration the mean year magnitude of Rdn (Table 1).

The percentage decrease in the number of EESU on days

with low or very high Rdn versus the middle-high Rdn

was correspondingly: –10.3% (–10.4 - –10.4) and –23.6%

(–32.9 - –16.1).

The relation of EESU with Rdn remained significant

after additional adjustment for WV (after adjustment for

the four confounding variables and WV p1,2 = 0.03, p2,3 =

0.01).

2.4

3.4

187173 259 345

Day sorted by Rdn value

EESU

Figure 3. The number EESU plotted against the day sorted by

Rdn value in ascending order. Polynomial model: thin line (0)

—raw data, thick line (5)—data adjusted for the four potential

confounding variables (Y, T, AP, RH) and APF-A.

Table 3. 95% Confidence intervals for three categories of Rdn

(low, middle-high and very high) and corresponding number of

EESU for raw data (EESU/0) and data adjusted for five vari-

ables - Y, T, AP, RH and APF-A (EESU/5).

Low Rdn

95% CI

n1 = 150

Middle-high Rdn

95% CI

n2 = 161

Very high Rdn

95% CI

n2 = 34

Rdn 0.83-0.92 1.69-1.80 3.05-3.77

EESU/0

2.47-3.02

P1,2 = 0.02

2.96-3.57

2.00-3.14

P2,3 = 0.07

EESU/5 2.67-3.11

P1,2 < 0.05

2.98-3.47

2.00-2.91

P2,3 = 0.005

Note: P1,2; P2,3 - significance of the difference in the number of EESU

between days with correspondingly: low Rdn and middle-high Rdn;

middle-high Rdn and very high Rdn.

4. DISCUSSIONS

4.1. The Relation between EESU and APF-A

To our knowledge, only one communication has been

published on the relation between natural APF and hu-

man behaviour. Green J.E. and Dunn F. [8] found a cor-

relation between the presences of strong infrasonic dis-

turbances generated by natural atmospheric phenomena

and automobile accidents, as well the schoolchildren

behavioural demonstrations of being unwell.

We found that the number of EESU was greater at

days with common middle and high APF-A compared to

the days with low APF-A. These findings suggest the

high sensitivity of people with suicidal psychopathology

to APF levels, which is in line with the some authors’

belief that weather sensitivity increases in people with

psychical disorders [19-22]. Obviously the APF middles

levels as well as the high ones were relevant external

stimulus to provocation of suicidal intentions. Previously,

the stimulating effects of artificial atmospheric pressure

oscillations in the range of their natural levels on human

normal purposeful behavioural activity were also re-

vealed in the experimental study [10].

In contrast, the lack of activating influences of APF at

days with their low levels seems to be the positive factor

favouring to decrease in risk of suicidal actions, as well

the incidence of EESU. The decrease in number of sui-

cidal injuries at days with low APF could be also con-

nected with increasing passiveness for the lack of APF in

the environment, which was previously assumed [10].

From this point of view, the low levels of APF can par-

ticularly interfere with transition from suicidal ideation

to suicidal action.

It follows from our results that the Y and T were im-

portant confounding variables for the relation between

EESU and APF-A. These variables can be associated

with certain slow time-varying environmental factors

such as seasonal changes in weather, certain physical

conditions and social aspects influencing on suicidal

events. In considerable numbers of studies the daylight

and sunlight duration, comfort ambient temperature, as

well the warm months of the year (particularly summer

and late spring) are considered to be an optimal condi-

tion for the suicide actions [3,4,7,23]. We found that

simultaneous effects of these two variables and the

APF-A on the number of EESU had opposite character.

Due to interfering effects of Y and T the significant rela-

tion between EESU and APF-A was found only after

adjustment for these two variables.

It is necessary to note that the present study demon-

strates the significant effects of natural APF-A having

lower values, than those in the experimental studies

[10,14]. Apparently biological effectiveness of natural

APF-A is depended on dose effects of their prolonged

actions.

L. A. Didyk et al. / HEALTH 2 (2010) 448-453

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4.2. The Relation between EESU and Rdn

The previous study showed that daily dynamics of APF

was characterized by pronounced regularity [12]. Ac-

cording to this regularity the mean hourly amplitude of

APF increases from night to day followed by a decrease

from day to night. Therefore, the possible association of

daily dynamics of APF with circadian rhythms of human

psychical activity could be suggested. From standpoint

of behavioural continuum from sleeping to high level of

vigilance the regular daily dynamics of APF could be

considered as favourable factor enabling an organism to

adopt to the needs of higher activity levels while awake.

We found that the number of EESU was significantly

decreased at days with low (СI = 0.83-0.92) and very

high (СI = 3.05-3.77) Rdn compared with middle-high

Rdn (СI = 1.69-1.90) closed to mean year values of Rdn

(СI = 1.43-1.62). These results indicated that the number

of EESU was greater at days when the ratio of diurnal

APF values to their preceding nocturnal values closed to

common mean values. When nocturnal APF were higher

or much less, than their diurnal values, the number of

EESU was decreased. Therefore, it could be suggested

that effectiveness of diurnal levels of APF in relation to

EESU was depended on the foregoing nocturnal levels.

As to the activating effects of APF the decrease in

their diurnal levels in comparison with the nocturnal

levels indicated the decrease in effectiveness of APF as

external provoking stimulus for the suicidal actions and

as a consequence the decrease in the number of EESU

during the daytime. The decrease in the number of

EESU at days when diurnal APF were highest in com-

parison with the nocturnal ones could be due to “para-

doxical” or antagonistic reaction with opposite character.

According to the opinion of Wein A.M. et al. [24], such

character of reaction could be evoked by irritant when

the initial level of activation was abruptly altered.

4.3. The Additional Findings and Possible

Implication of the Results

The previous study showed interrelated effects of high

APF and WV on the number of emergency transport

events due to circulatory system diseases [12]. Possible

reason for the independent on WV significant decrease

in EESU on days with low APF-A revealed in this study

could be the non-linear relation between these two at-

mospheric variables [18]. According to this non-linearity,

the causal relation between APF and WV is well pro-

nounced only during strong wind, as the low WV is in-

sufficient contributor to the APF generation. Apparently,

due to the weak association of APF with low WV the

relation between EESU and APF-A remained significant

after adjustment for the WV.

The additional findings obtained in this study did not

support also the conception of a spring peak of suicide

incidence [23-25]. According to our data the number of

EESU (without the reference to the sex difference) was

higher during warmer time of the year in Kyiv. This time

was summer and early autumn. Though, Parker G. and

Walter S. [26] reported an early summer peak for both

genders and early autumn peak in women.

As the future implication of this study results we sug-

gest that the meteorological forecast of APF levels woul-

d be helpful for hospital emergency services in order to

be able to prepare for potential increases in workload

due to increase in traumatic accidents. The evidence, re-

ceived in this study may be useful for the behavioural se-

lf-control in individuals with propensity toward suicidal

ideation, as well for the relevant medical professionals.

5. CONCLUSIONS

The results of this study corroborate the suggestion that

mean daily amplitudes of APF and ratio of diurnal levels

of APF to their nocturnal levels are related to the risk for

injuries due to psychopathological suicidal behaviour.

In this preliminary study we only found threshold ef-

fects of APF. The essential limitation of our study was

the moderate climatic conditions of Kyiv locality with

still or slightly windy weather prevailing. Perhaps, the

functional shapes of the relation of EESU with APF are

more complex than those revealed in the present study.

To clear up this question it will be necessary to extend

the observation over a longer period and different geo-

graphical and climatic areas, especially those where

strong atmospheric pressure perturbation are frequent.

Because there may be further uncontrolled factors our

findings require additional corroboration.

6. ACKNOWLEDGEMENTS

This study was supported by the NATO Program Security Through

Science, Collaborative Linkage Grant number 98376, and by funds

from the University of Antwerp (BOF-NOI).

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