The influences of meteorological factors on the health and functional state of human ()
1. INTRODUCTION
Weather conditions include many different factors: the atmospheric pressure and its oscillations, temperature, humidity and wind velocity. Each of them has an impact on the mood and the functional state [FS] of humans. Functional state of man is an integrative characteristic of an individual’s efficiency of his role and activities involved in its implementation of systems according to the criteria of reliability and internal rates of activity [1].
Pristrom & Mrochek 2002 stated [2] that in the developed countries, approximately one third of the population has an increasing sensitivity to the change of weather. Negative symptoms such as headache, weakness, pain in joints and palpitation may appear at the same time or just before a sudden change in temperature and atmospheric pressure. Severity of the symptoms depends on the adaptation to such changes, age and diseases. The physiological reactions sometimes can occur without being perceived consciously. Cognitive functions are most sensitive to meteorological changes. Short term memory, attention and reaction time are sensitive to rapid changes in weather factors [3,4]. The effect of the environmental factors increases by their simultaneous action, even if the amplitude of each factor is separately too small for triggering the reaction [3,5].
1.1. Temperature Effects
Marchenko et al. 1998 [6] have shown that temperature conditions influence the processes of thermoregulation and metabolism, change muscular and nervous activity and biochemical and bioelectric processes. Low air temperature affects the strongly cognitive activity [7]. Low temperature reduces cognitive activity, attention and concentration via distraction and increase in arousal [4,8]. The impact of temperature on the organism to a great extent depends on the humidity of air. At heightened humidity, the impact of high and low temperature is increased [6].
1.2. Atmospheric Pressure Effects
Changes of atmospheric pressure mechanically influence circulation by constriction of superficial capillaries, located in the skin and respiratory pathways. Low atmospheric pressure slows down heart rate and increases the respiratory volumes [9]. The increase of atmospheric pressure decreases the number of leucocytes, mainly neutrophils [9]. The changes of the number of neutrophils and leukocytes are the indexes of changing the general state of the autonomic nervous system. Lowering of atmospheric pressure activates the sympathetic nervous system, causes the increase of reaction time, suppresses mood and reduces ability to work. Oppositely, the increase of atmospheric pressure induces activation of parasympathetic nervous system [9].
1.3. Wind Velocity Effects
The effect of wind is ambiguous. Influences of wind on human health are due to effects of environmental concomitants such as ambient temperature, humidity, atmospheric pressure and positive ion concentrations [10]. In cold weather, wind increases heat irradiation, and also potentates the influence of humidity. Influence of wind velocity on organism will mediate directly on skin, and by heating or cooling, this effect depends on other factors like relative humidity and temperature. A climate with large fluctuations in temperature and high wind velocity is unfavorable for people, predisposition to the increase of arterial pressure. Wind speed, exceeding 10 m/s, negatively affects the wellbeing of patients [6].
Rapid changes of air pressure, air temperature, hot, sweltering and sultry days, very frosty days, days with strong or foehn wind, days with thunderstorms, fog and haze were selected as unfavorable weather factors. They give an occasion for strong psychical stress [11]. The effects of winds blowing from the mountains (foehn wind) on human mental activity, characterized by parameters such as reaction time and duration of active attention, and indirect indications such as the behavior resulting in traffic accidents were considered in a number of studies [12,13]. Lee and Garraway [14] found a significant effect of wind strength on the risk of sport injuries. The heightened anxiety levels in people with mental disorders increase in suicide incidence and the more frequent occurrences of cardiac arrhythmias on days with strong wind are likely, at least partly, to be due to some biological response to wind-generated rapid atmospheric pressure fluctuations (APF) [15-17]. The meanings of the effects of wind are attributed to concurrent rapid APF.
1.4. Atmospheric Pressure Fluctuations Effects
There are emerging number of studies of effects air pressure fluctuations and their impact on human health and wellbeing. The most powerful source of APF in stormy weather is the chaotic turbulent airflows induced by strong wind [17-24]. The influence of APF may createsubstantial changes in the attention, working memory, cognitive performance and mental flexibility. Therefore, APF are supposed to be able to raise the risk of neurological disorders [9]. The important feature of APF is that man does not feel their alterations, and therefore, cannot consciously estimate their action on the mental state and wellbeing [17]. The adverse effects of AFP during stormy weather storm on road accidents were reported [24]. This can be explained by the observation that modeled APF in the infrasound frequency range (0.003 Hz < f < 1 Hz ~ 1 sec - 20 min) can affect cognitive functions, especially attention [2,17-22,24,25]. APF penetrate buildings [22,26] and, therefore, could be responsible for weather sensitivity symptoms not only outdoors, but also indoors. It is believed that natural APF could affect the human body through the reactions of tympanic membrane [24]. Some authors suggested that the special area, pars flaccida in the tympanic membrane containing elastin fibers, is actually a middle ear sensor for pressure fluctuations [27,28]. In favor of this view, the mechanical reactions of pars flaccida in response to very little changes in the middle ear pressure, as well as to slight pressure oscillations in far infrasound range, were demonstrated by the experimental studies on animals [27, 29].
Some authors believe that there is a pathway, through which changes in the pressure are transmitted from the middle ear to the inner ear and influence the activity of the otolithic receptors. This activity consequently affects the firing rates of the vestibular afferent fibers and of the neurons in the vestibular nucleus [30]. It is also shown that vestibular activity is dependent on the rates of ambient pressure changes in the middle ear. It is larger under higher rates of pressure changes [31]. In our experiment we wanted to evaluate effects of APF using simple sensory-motor reaction time task and wellbeing selfassessment.
1.5. Reaction Time Task and Psychological Self-Assessment
Reaction time (RT) depends on the state of central nervous system [32-36]. RT increases in conditions of reduced attention [33]. It was already shown that RT is a sensitive measure of meteorological responses. RT considerably deteriorates at high temperature and lowering of atmospheric pressure [9,25,37].
Cold ambient temperature decreases body core temperature and reduce RT [38,39]. Seasonal variation of mood is characterized by onset of depression in winter/autumn [40]. Seasonal depression and other seasonal affective disorder occurring during autumn and winter months are most common in young women, although it can affect men or women of any age, these seasons’ negatively affect wellbeing, activity and mood. Studies based on violent homicides, suicides, and aggressive behaviors have repeatedly demonstrated seasonal characteristics, typically with peaks in the spring [41-43].
We expected that increased APF can contribute to seasonal depressive symptoms. The aim of our study was to show effects of APF on functional state and wellbeing self-report. Between subject variability was correlated to the current meteorological parameters of interest. Conventional meteo-data (air temperature, wind velocity and atmospheric pressure) were used as possible confounds. Therefore, we compared effects of temperature, atmospheric pressure, wind velocity and fluctuations of atmospheric pressure on self-estimated wellbeing, activity and mood and on reaction time task. In this paper different seasons were used for the study of effects of various weather conditions on wellbeing, activity and mood and reaction time task in unlike ethnic groups. Because of the literature data, the various effects of meteorological parameters and APF on the functional state of men and women were expected in different seasons. We expected that APF and wind velocity have more negative effects on both RT and psychological self-assessment because of distraction and increase of arousal level.
2. MATERIAL AND METHODS
2.1. Participants
The study was performed in tow geographical regions: Kyiv (Ukraine) and Shiraz (Iran) and during three distinct seasons: spring (14 March to 13 April), autumn (28 September to 28 October) in Kyiv and winter (9 February to 4 April) in Shiraz. In the spring 48 men and 27 women, in autumn 15 men and 20 women and in winter 25 men were studied. On the whole 135 volunteers in three groups were studied. Ages of participants were 15 - 30 years old. The study design was approved by local ethical committee.
2.2. Experimental Design
At the beginning of the experiment, all the subjects sign the informed consent and fill the questionnaires about “wellbeing, activity and mood” WAM [44]. Then we measured the simple reaction time (RT) to visual stimuli by the computer program designed by us on the personal computer (monitor 14", 640/480 Pixels). The stimulus signal was a white square with an area of 1000 pixels on the black background. Linear sizes of the side of the square were 11 mm, angular sizes—1˚20′. General radiance was measured by “Digital Luxmeter MS6610”. The luminosity of the workplace at a distance of 0.5 m from the monitor was established at the level 6 - 15 Lux. 100 signals were exposed with intervals of 1500 - 3000 ms randomly changed.
Volunteers who stayed in front of the monitor (distance from the monitor to the eyes was about 50 cm), were given the following instructions: “On presence of every stimulus you should press any key on the keyboard as fast as possible. Not be distracted, do not speak during the test, do not press the key prematurely i.e. before the appearance of the stimulus.” Responses less than 100 ms were considered as errors, and responses that took longer than 500 ms were excluded, too. The experimental task was as long as 5 minutes. First 10 trails and total average of reaction times were used for estimation of individual average reaction rime (RT) values and standard deviations (SD) for further analysis. Standard deviation measures the degree of variability or diversity among variables. Standard deviation is a measure of variability around a mean. Standard deviation is important because it aids in making statistical studies and researches more reliable, accountable and valid.
The average increase of time of RT and SD was interpreted by us as a decrease of functional state. First 10 values where specifically valuable to evaluate ability to gain rapidly simple task related skills. The total RT was the measures of ability of have high and sustained performance.
2.3. Meteorological Data Collection
Monitoring of APF was carried out continuously, round-the-clock, during all the time of research by the electronic micro barometer “Atmospher-P1” (“Dobruyshlyah”, Kyiv, Ukriane), which was disposed outdoors. Atmospheric pressure oscillations were recorded from 650 to 1080 Pa (from 489 to 812 mmHg), with the sensitivity of 1 Pa and acquisition rate of 1 sec. Recorded information was written down in the memory of the device and was passed for storage and processing on a personal computer.
The data of APF were analyzed with a specialized program on the basis of the package of MatLab (The MathWorks Inc.). By the methods of digital spectral filtration (rapid transformation of Fourier) to select pressure fluctuation in 5 ranges of periods: I—from 120 s to 1200 s; II—from 20 s to 120 s; III—from 10 s to 20 s; IV—from 5 s to 10 s; V—from 3 s to 5 s. Also, for each of 5 noted ranges, analysis was done for every hour of frequency constituent (harmonic) with the maximal value of amplitude and the hourly amplitude of fluctuations in this range was calculated. From APF parameters we have taken AD (the detected amplitude of signal in the range).
Standard meteorological data (temperature of air, wind velocity, atmospheric pressure,) in the period of experiment were obtained from the meteorological center of airport of Juliany of Kyiv, Ukraine and the national meteorological center of Shiraz, Iran. Following statistical processing were made with the program of Statistica 8.0 (StatSoft, USA). The relationships between psychological and physiological measures and current meteorological parameters were estimated by Spearman rank order correlation and General Linear Models.
3. RESULTS
Table 1 shows the means and Standard Errors of groups’ characteristics in 3 season of experiment.