title: Changes in ischemic stroke occurrence following daylight saving time transitions.
abstract: Circadian rhythm disruption has been associated with increased risk of ischemic stroke (IS). Daylight saving time (DST) transitions disrupt circadian rhythms and shifts the pattern of diurnal variation in stroke onset, but effects on the incidence of IS are unknown.
  
  
  
  Effects of 2004-2013 DST transitions on IS hospitalizations and in-hospital mortality were studied nationwide in Finland. Hospitalizations during the week following DST transition (study group, n = 3033) were compared to expected hospitalizations (control group, n = 11,801), calculated as the mean occurrence during two weeks prior to and two weeks after the index week.
  
  
  
  Hospitalizations for IS increased during the first two days (Relative Risk 1.08; CI 1.01-1.15, P = 0.020) after transition, but difference was diluted when observing the whole week (RR 1.03; 0.99-1.06; P = 0.069). Weekday-specific increase was observed on the second day (Monday; RR 1.09; CI 1.00-1.90; P = 0.023) and fifth day (Thursday; RR 1.11; CI 1.01-1.21; P = 0.016) after transition. Women were more susceptible than men to temporal changes during the week after DST transitions. Advanced age (>65 years) (RR 1.20; CI 1.04-1.38; P = 0.020) was associated with increased risk during the first two days, and malignancy (RR 1.25; CI 1.00-1.56; P = 0.047) during the week after DST transition.
  
  
  
  DST transitions appear to be associated with an increase in IS hospitalizations during the first two days after transitions but not during the entire following week. Susceptibility to effects of DST transitions on occurrence of ischemic stroke may be modulated by gender, age and malignant comorbidities.
authors.affiliation: Department of Neurology, North Karelia Central Hospital, Joensuu, Finland; Neurology, University of Turku, Turku, Finland; Division of Clinical Neurosciences, Turku University Hospital, Turku, Finland.
authors.forename: Jussi O T
authors.initials: JO
authors.lastname: Sipilä
authors.affiliation: Neurology, University of Turku, Turku, Finland; Division of Clinical Neurosciences, Turku University Hospital, Turku, Finland. Electronic address: jori.ruuskanen@tyks.fi.
authors.forename: Jori O
authors.initials: JO
authors.lastname: Ruuskanen
authors.affiliation: Clinical Research Center, Turku University Hospital, Turku, Finland; Department of Public Health, University of Turku, Turku, Finland.
authors.forename: Päivi
authors.initials: P
authors.lastname: Rautava
authors.affiliation: Research Centre of Applied and Preventive Cardiovascular Medicine, University of Turku, Turku, Finland; Heart Center, Turku University Hospital, Turku, Finland.
authors.forename: Ville
authors.initials: V
authors.lastname: Kytö
mesh_terms: D000367:Age Factors; D000368:Aged; D002545:Brain Ischemia / Q000453:epidemiology* / Q000503:physiopathology / Q000628:therapy; D002940:Circadian Rhythm; D015897:Comorbidity; D005260:Female; D005387:Finland / Q000453:epidemiology; D006760:Hospitalization; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D016016:Proportional Hazards Models; D012307:Risk Factors; D012621:Seasons; D012737:Sex Factors; D020521:Stroke / Q000453:epidemiology* / Q000503:physiopathology / Q000628:therapy; D013997:Time Factors
keywords: Cerebrovascular disease; Chronobiology; Circadian rhythm; Circadian rhythm disturbance; Circadian rhythm misalignment