title: Cerebral infarction versus solar and geomagnetic activity: a cross-regression study.
abstract: BACKGROUND
  In the course of occurrence of cerebral infarction, cerebral hemorrhage and subarachnoidal hemorrhage episodes, periodicities resembling those found in the solar and geomagnetic activity were observed by Kovác and Mikulecký in 2005.
  
  
  OBJECTIVE
  To investigate putative relationships between two indices of solar activity and one index of geomagnetic activity on one side and the occurrence of cerebral infarction on the other.
  
  
  METHODS
  In addition to the 192 monthly cases out of 6100 new cases of cerebral infarction that occurred between January 1989 and December 2004, monthly averages for Wolf numbers, solar flares index and Ap index were included in the analysis. The cross-correlation between each cosmo-geophysical variable on the one hand and the number of new cases of the disease on the other was computed. The quadratic regression with the chosen time delay was also studied using, separately, the Wolf numbers, solar flares and Ap index as the explanatory variable and the number of cases of cerebral infarction as the responding variable.
  
  
  RESULTS
  Significantly negative correlation coefficients between the monthly means of the Wolf numbers, of solar flares and of Ap index on the one hand and monthly numbers of new cases of the disease on the other were found for the delays between -6 and +17 months. The cross-regression results for the delay of +5 months (infarction delayed after each cosmo-geophysical variable by 5 months) displayed a linear decrease except for the Wolf numbers where the parabolic decrease of cases was significant.
  
  
  CONCLUSIONS
  An increased intensity of the studied cosmo-geophysical parameters appears to be significantly connected with decreased occurrence of cerebral infarctions, and vice versa. This effect seems to last up to 17 months. The results are supported by a few similar findings in the literature. Putative cosmo-biomedical connections warrant further study to verify them in larger samples and longer time scales. If confirmed, their mechanisms should be elucidated.
authors.affiliation: Department of Biometry and Statistics, Neuroendocrinology Letters, Stockholm, Sweden. statistics@nel.edu
authors.forename: Miroslav
authors.initials: M
authors.lastname: Mikulecký
authors.forename: Jaroslav
authors.initials: J
authors.lastname: Strestík
mesh_terms: D002544:Cerebral Infarction / Q000453:epidemiology*; D006801:Humans; D015994:Incidence; D008280:Magnetics; D010507:Periodicity; D012044:Regression Analysis; D018154:Slovakia / Q000453:epidemiology; D019445:Solar Activity