Seasonal variation of mortality in the Antiarrhythmics Versus Implantable Defibrillators (AVID) study registry.
OBJECTIVE
We postulated that the pattern of death would be nonrandom with respect to temporal variables.


BACKGROUND
Previous studies have demonstrated increased sudden death is associated with periods of relative stress, and overall mortality is associated with temporal variables.


METHODS
In the Antiarrhythmics Versus Implantable Defibrillators (AVID) registry, vital status was obtained for 4,450 patients (who had a recent episode of sustained ventricular arrhythmias or unexplained syncope and inducible ventricular tachycardia) through the National Death Index Service as of December 31, 1997 (follow-up 25.5 +/- 13.7 months).


RESULTS
Mortality was not associated with the day of the week or with holidays but was associated with season (P = .033). Seasonal variation was present both in northern and southern sites. Mortality was higher during the winter months compared to the remaining months (111.2% in winter vs 96.5% in other months, P = .036). In addition, increased mortality was associated with a high-risk season variable defined (prior to evaluation of treatment arm associations) as spring in the north and winter in the south (P < .001). The hazard ratio for death associated with this "high-risk season" measured 1.25 (P = .001) compared to the other seasons in each region. A test of interaction between "high-risk" season and implantable cardioverter-defibrillator (ICD) status suggested that the group with ICDs experienced reduced mortality during the "high-risk season" compared to the group without ICDs (P = .047).


CONCLUSIONS
Mortality was higher in the winter months and in the respective regional "high-risk" seasons. Furthermore, seasonal variation in mortality may have been due to variation in sudden arrhythmic death, and associated increases in mortality were reduced by ICD therapy.
Page
Richard L
RL
Department of Internal Medicine, Cardiology Division, University of Washington School of Medicine, Seattle, 98195, USA. rpage@u.washington.edu
Zipes
Douglas P
DP
Powell
Judy L
JL
Luceri
Richard M
RM
Gold
Michael R
MR
Peters
Robert
R
Russo
Andrea M
AM
Bigger
J Thomas
JT
Sung
Ruey J
RJ
McBurnie
Mary Ann
MA
D000889:Anti-Arrhythmia Agents / Q000627:therapeutic use*; D002940:Circadian Rhythm; D016757:Death, Sudden, Cardiac / Q000453:epidemiology* / Q000517:prevention & control; D017147:Defibrillators, Implantable / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012042:Registries; D012621:Seasons; D013997:Time Factors; D014481:United States / Q000453:epidemiology; D014693:Ventricular Fibrillation / Q000188:drug therapy / Q000401:mortality* / Q000628:therapy
D000889:Anti-Arrhythmia Agents