We investigate the impact of solar activity changes on mortality from cardiovascular causes of death in the period 1994-2011 in the Czech Republic. This period coincides with the time of solar cycle no. 23 and the surrounding minima when there was an unusually low level of solar activity. We use long-period daily time series of numbers of deaths by cause, solar activity indices (the relative sunspot number, and the intensity of solar radio flux), geomagnetic indices (Kp-the planetary index that indicates the fluctuation rate of horizontal components of the geomagnetic field, the Auroral Electrojet, and the disturbance storm time), and physical parameters describing the ionospheric effects (the critical frequency of the ionospheric F2 layer and the content of free electrons in the ionosphere). The results of the analysis confirm the hypothesis that there is no direct correlation between the geomagnetic solar index, Kp, and the number of deaths from acute myocardial infarction (code I21) or brain stroke (code I64) during the maxima of the solar cycle. On the other hand, the ionospheric parameters explain a greater part of the variability in the number of deaths for acute myocardial infarction or brain stroke than the model with solar parameters. The analysis shows that, because the values are geographically specific, the ionospheric parameters may describe the variability in the number of deaths from cardiovascular causes better than the solar indices. The cardiovascular diseases thus respond to the changes in the solar activity and to abnormal solar events indirectly through a concentration of electrical charges in the earth's environment.
Keywords: Mortality; circulatory system diseases; cluster analysis using time; solar indices.
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