title: Ambient temperature and activation of implantable cardioverter defibrillators.
abstract: The degree to which weather influences the occurrence of serious cardiac arrhythmias is not fully understood. To investigate, we studied the timing of activation of implanted cardiac defibrillators (ICDs) in relation to daily outdoor temperatures using a fixed stratum case-crossover approach. All patients attending ICD clinics in London between 1995 and 2003 were recruited onto the study. Temperature exposure for each ICD patient was determined by linking each patient's postcode of residence to their nearest temperature monitoring station in London and the South of England. There were 5,038 activations during the study period. Graphical inspection of ICD activation against temperature suggested increased risk at lower but not higher temperatures. For every 1 °C decrease in ambient temperature, risk of ventricular arrhythmias up to 7 days later increased by 1.2 % (95 % CI -0.6 %, 2.9 %). In threshold models, risk of ventricular arrhythmias increased by 11.2 % (0.5 %, 23.1 %) for every 1° decrease in temperature below 2 °C. Patients over the age of 65 exhibited the highest risk. This large study suggests an inverse relationship between ambient outdoor temperature and risk of ventricular arrhythmias. The highest risk was found for patients over the age of 65. This provides evidence about a mechanism for some cases of low-temperature cardiac death, and suggests a possible strategy for reducing risk among selected cardiac patients by encouraging behaviour modification to minimise cold exposure.
authors.affiliation: Department of Social and Environmental Health Research, London School of Hygiene and Tropical Medicine, University of London, 15-17 Tavistock Place, London WC1H 9SH, UK. lmcguinn@live.unc.edu
authors.forename: L
authors.initials: L
authors.lastname: McGuinn
authors.forename: S
authors.initials: S
authors.lastname: Hajat
authors.forename: P
authors.initials: P
authors.lastname: Wilkinson
authors.forename: B
authors.initials: B
authors.lastname: Armstrong
authors.forename: H R
authors.initials: HR
authors.lastname: Anderson
authors.forename: V
authors.initials: V
authors.lastname: Monk
authors.forename: R
authors.initials: R
authors.lastname: Harrison
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D001145:Arrhythmias, Cardiac / Q000401:mortality* / Q000517:prevention & control*; D017147:Defibrillators, Implantable / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D018570:Risk Assessment; D012621:Seasons; D017678:Sex Distribution; D015996:Survival Rate; D013696:Temperature; D006113:United Kingdom