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THE ROLE OF AIR POLLUTING SUBSTANCES IN THE DEVELOPMENT OF STROKE IN THE CONDITIONS OF THE LARGE INDUSTRIAL CITY
Novosibirsk State Medical University, Novosibirsk
2City clinical hospital №1, Novosibirsk
3Novosibirsk Research Institute of Hygiene, Novosibirsk
M.V. Yashnikova12, Ye.L. Poteryayeva13, B.M. Doronin1
The results of examination of538 patients with stroke are presented in the article - 280 men (52.0%), 258 women (48.0%); and the structure of seasonal incidence of stroke is studied. At the same time, there was assessed the influence of atmospheric environmental factors on the level of the given morbidity in the conditions of the industrial city of Western Siberia. According to the results of the study, the incidence of stroke is the leader in spring (during the period of high atmospheric pollution). A strong direct correlation was found between the number of stroke disease patients and the concentration of nitrogen dioxide and suspended solids in the air in certain months of a year.
Key words: stroke, seasonality, nitrogen dioxide.
Stroke still presents an important medical and social problem both in the world and in Russia, which is conditioned by high indexes of morbidity, lethality and invalidization. According to the statistical analysis [4], about 0,5 million people in Russia suffer from stroke every year with the morbidity rate 3 per 1000 people. Mortality rate due to stroke holds the stable second position in the stricter of total population mortality trailing only the cardiac pathology [4].
It is considered, that the contribution of the external environment (ecological factors) to the deterioration of health and main forms of pathology in Russia ranges within 40-60%. One of the environmental factors mostly influencing the state of health of the majority of the Russian Federation population is the quality of air.
The climate of Novosibirsk and its surroundings is continental. A distinctive feature of the city climate is a great number of inversions, which considerably reduce the ability of the atmosphere to dissipate contaminating substances.
Research objective: to evaluate the influence of atmospheric ecological factors on the level of stroke morbidity in the conditions of the industrial city of Western Siberia.
Materials and methods
There were analyzed hospital medical histories, medical certificates of death, forensic medical reports, ambulance calls, out-patient medical records including all new and recurrent stroke cases (in-patient and out-patient), lethal and not lethal, having been developing in the permanent residents of one of Novosibirsk districts during 3 years. The age of patients constituted from 25 to 74 years. All studies were performed according to the protocol including a standard questionnaire "Register of stroke and its risk factors".
The study considered daily average concentrations of contaminating substances during the year in the air of the studied district according to the data of the Department of social-hygienic monitoring of the city center of Rosbotrebnadzor (suspended materials, carbon oxide, sulphur dioxide, carbon, nitrogen dioxide, formaldehyde, ammonia, benza-pyrene). The monitoring of the city atmosphere air is performed by the Novosibirsk Center of Hydro-meteorology and Monitoring of Environment with Functions of Regional Specialized Meteorological Center of World Service of Weather at 10 fixed monitoring stations. The studied district contains two fixed stations.
Results and discussion
There were examined 538 patients with stroke: 280 men (52,0%), 258 women (48,0%). According to the WHO classification, the patients were divided into age groups: young age (from 25 to 44) - 24 people (4,2%), middle age (from 45 to 59) - 185 people (34,8%), elderly age (from 60 to 74) - 329 people (61%).
The study of the seasonal structure of stroke revealed the following frequency: winter period - 115 people (21,4%), spring period - 161 people (29,9%), summer period - 120 people (22,3%), autumn period - 142 people (26,4%).
The peculiar feature of the ecological situation is the concentration of the industrial potential of the region in the city. The highest level of contamination is registered in the studied district on a number of parameters (basic contaminating substances and specific ingredients) being detrimental to the cardio-vascular and nervous systems. Novosibirsk is characterized by increased concentrations of suspended materials during the warm period of the year when the air is dominated by natural substances (soil dust) in combination with suspended substances of industrial origin.
The excess of maximum permissible concentration (MPC) of carbon oxide is registered at the "auto stations". The level of air contamination is mainly formed as a result of emissions of low uniform sources (mainly automobile transport), thus, there are observed comparatively gradual changes of nitrogen dioxide concentration month-over-month. During the cold period due to the load of the heating system, monthly concentrations of nitrogen dioxide are a bit higher. The increased concentration of formaldehyde is observed during the warm period of the year, which is connected, with the rise of daily temperature and photochemical transformations. The growth of carbon content in the air is usually observed during the cold half of the year, which is conditioned by increased emissions of boiler and electric stations.
To evaluate the influence of the air contamination level on the rate of morbidity there was determined the correlation coefficient. There were stated positive correlations for two contaminating substances.
A strong direct correlation is observed (r=0,72) between the number of stroke patients and the level of nitrogen dioxide concentration during particular months of the year (Figure 1). The changes of both parameters are parallel: increase during winter till May, decrease in July, the peak of increase in August and September.
The exiting correlation can be explained by the proved influence of nitrogen dioxide on the state of brain blood circulation due to the appearance of hypoxic effect and changes of blood rheological properties, which, in its turn, leads to thrombi formation.
Figure 1.
Correlation of relative number of patients and relative concentration of nitrogen dioxide
The average direct correlation (r=0,31) is revealed between the number of stroke patients and the level of suspended materials concentration (Figure 2). The parallel changes of pa-
rameters are observed during the first months of the year (gradual growth from January till May) and during the autumn period (reduction of both parameters).
Figure 2.
Correlation of relative number of patients and relative concentration of suspended materials
It is known, that suspended materials stimulate the development of phagocytosis leading to peroxide stress, which causes membrane pathological effect, and specifically in cardiomy-ocytes. Moreover, there is proved the correlation
of the development of cardio-vascular pathology (arterial hypertension and ischemic heart disease) in persons with long-term exposure to dust - r=0,71 (Vavilova V.A., 2005). Arterial hyperten-
sion and ischemic heart disease are the risk factors of stroke development.
To evaluate the effect of the air contamination level on the disease outcome there were calculated the average number of lethal cases every month and further their relative values. The average cor-
relation (r=0,48) was determined between the number of dead patients and the level of nitrogen dioxide concentration (Figure 3). Figure 3 shows that the changes of these parameters and the overall number of stroke patients are parallel.
0 n-i-i-i-i-i-i-i-i-i-i-i-
1 2 3 4 5 6 7 8 9 10 11 12 months
Figure 3.
Correlation of average number of stroke patients, dead patients and relative concentration of nitrogen dioxide
For the other contaminating substances (benza-pyrene, sulphur dioxide, carbon, ammonia, formaldehyde and carbon oxide) there was revealed a slight and negative correlation with the level of stroke morbidity and lethality.
The obtained data on the correlation of stroke morbidity level and air contamination can be explained both by the direct influence of chemical substances on neurons, nerve fibers and synaptic connections, and by the effect on the cardio-vas-cular system (blood rheological properties, vascular endothelium, change of peripheral circulation, heart rhythm disorder). Furthermore, it should be taken into consideration, that in the zone of industrial discharge can appear patients with chronic diseases (arterial hypertension, ischemic heart disease, atherosclerosis, diabetes mellitus), the course of which is worsened. In some cases, the chemical substances themselves can lead to the development of pathology.
The stated correlations between the number of stroke patients and the level of contaminating substance concentration in the air of Novosibirsk corresponds to the results of standardized epide-miological research conducted in terms of the international program MONICA which revealed an expressed dependence of the growth of cardio-vas-cular disease cases on the increase of CO, SO2 and dust particle concentration in the air.
Conclusion
The seasonal structure of stroke morbidity in the conditions of the large industrial city of Western Siberia is prevailed by the spring period. During the period of increased atmosphere con-
tamination, there is revealed the growth of stroke morbidity level. The obtained data are the background for making organizational and management solutions: improvement of environment monitoring during the period of maximum pollution, reduction of concentration of such substances as nitrogen dioxide, suspended materials.
References
1. Vavilova V.A. Prevention of cardio-vascu-lar pathology in the workers of dust exposed occupations. Moscow, 2005.
2. Emissions of contaminating substances into the atmosphere of cities and districts of Novosibirsk Oblast in 2015. Statistical bulletin. Novosibirsk, 2016.
3. Klochikhina O.A., Stakhovskaya L.V. An analysis of epidemiological indices of stroke based on the data of a regional population register from 2009 to 2012. S.S. Korsakov Journal of Neurology and Psychiatry. 2014; 6: 63-68.
4. Starodubtseva O.S., Begicheva S.V. Analysis of stroke incidence using informational technologies. Fundamental research. 2015; 2(8): 424-427.
Contacts:
Corresponding author - Yashnikova Mariya Vik-torovna, Candidate of Medical Sciences, high level certificate physician-neurologist of the City clinical hospital №1, Novosibirsk. 630047, Novosibirsk, Zalesskogo Ulitsa, 6-4. Tel.: (383) 2261685. Email: yash-maria@mail.ru
