The goal of this study was to determine whether differences exist in the frequency of paroxysmal atrial fibrillation and stroke (cerebrovascular accident) on days of different geomagnetic activity levels. Geomagnetic activity was divided into four levels: quiet (I degree), unsettled (II degree), active (III degree), and stormy (IV degree). Measurements were made according to the six highest hourly geomagnetic parameters, in nanotesla units, over 24 hours. The study period covered 1185 consecutive days, from January 1990 to March 1993. All patients treated in the Admissions Department of a major multiprofile university hospital for stroke (cerebrovascular accident) (977 patients) or paroxysmal atrial fibrillation (653 patients) were included. Groups were also divided by sex and age (< or = 65 years vs. > 65 years) for comparison.
Results: (1) There was a significant negative correlation between daily paroxysmal atrial fibrillation and geomagnetic activity level (r = 0.976, p = 0.02); (2) The absolute number of daily admission for paroxysmal atrial fibrillation was higher on geomagnetic activity I degree days than on IV degree days (p < 0.004); (3) Stroke showed the same negative correlation with geomagnetic activity as paroxysmal atrial fibrillation, but only in males 65 years of age or less (r = 0.976, p = 0.027) suggesting a predominantly arrhythmic origin of stroke (cerebrovascular accident) in this group; (4) The male/female ratio for stroke was also adversely correlated with geomagnetic activity (r = 0.99, p = 0.0008), with the highest absolute number occurring on geomagnetic activity I degree days (X2 = 4.538, p = 0.03). These data are in accordance with previous studies showing increased heart electrical instability during periods of lowest geomagnetic activity.