title: Secular rhythms and Halberg's paraseasonality in the time occurrence of cerebral stroke.
abstract: OBJECTIVE
  To obtain the optimal information concerning the time course of the morbidity od cerebral stroke.
  
  
  BACKGROUND
  Recently, long years' cycling, similar to that in sun and geomagnetic activity, is observed in various biomedical variables. Other discovery is that of transyear (over one year) and cisyear (under one year) rhythms,originating also in the sun, in medicine.
  
  
  METHODS
  There were 6100 patients with cerebral infarction, 415 with intracerebral and 277 with subarachnoid hemorrhage admitted at Clinic of Neurology in Nové Zámky (area with 70 km radius and 180 000 inhabitants). Their monthly numbers were registered since January 1989 up to December 2004.
  
  
  METHODS
  The data were processed by Halberg's cosinor regression. Presence of linear trend and of the period lengths of 10.5 (solar Schwabe-cycle), 5.25, 7.04 (geomagnetic activity cycling), 3.52, 1.70, 1.50, 1.30 (solar wind cycling), 1.20, 1.00 and 0.50 years was tested. Level of statistical significance was set at alpha = 0.05.
  
  
  RESULTS
  In all three time series, significant linear trends were found with the estimated monthly increase by 0.8% of the estimated starting mesor value for infarction, 1.2% for cerebral and 1.9% for subarachnoid hemorrhage. Both the solar and geomagnetic cycling with their second harmonics were significant in all three clinical diagnoses. The transyear with period length of 1.3 year was significant in both hemorrhages while in infarction only its borderline significance was achieved. Nevertheless, its amplitude was always higher (by 15 to 83%) than that of 1.00 year estimated cosinusoid.
  
  
  CONCLUSIONS
  All presented time series document increasing trends in the morbidity on cerebral stroke in the given geographic area. The presence of secular, years lasting cycles adds to relatively long list of similar chronocosmoepidemiologic analyses, so far generally ignored due to insufficient understanding of inferential statistics and chronobiology among doctors. The transyear paraseasonality represents a new element in these studies. To honour the nestor of the world chronobiology, who highly acknowledged the work of Ladislav Dérer, the designation "Halberg's paraseasonality" is proposed (Tab. 2, Fig. 3, Ref. 17).
authors.affiliation: Clinic of Neurology, Faculty of St. Ladislaus, Nové Zámky, Slovakia. kovacm@nspnz.sk
authors.forename: M
authors.initials: M
authors.lastname: Kovac
authors.forename: M Sn
authors.initials: MS
authors.lastname: Mikulecky
mesh_terms: D002909:Chronobiology Phenomena; D006801:Humans; D010507:Periodicity; D012621:Seasons; D018154:Slovakia / Q000453:epidemiology; D019445:Solar Activity; D020521:Stroke / Q000453:epidemiology*