Resident Centre Hospitalier Universitaire de Sherbrooke Sherbrooke, Quebec, Canada
Background: Daylight saving time (DST) transitions disrupt circadian rhythms, potentially influencing cardiovascular events. European studies have demonstrated a modest increase in myocardial infarction (MI) risk following DST transitions, particularly after the spring transition. These findings prompted the European Parliament to recommend abolishing DST, though the initiative was delayed due to the COVID-19 pandemic. North American studies, however, have reported conflicting results regarding DST’s association with MI incidence. To our knowledge, there is no Canadian studies on the subject.
METHODS AND RESULTS: This retrospective, single-center study analyzed data from 49,669 patients admitted for MI (STEMI, NSTEMI) at the Centre Hospitalier Universitaire de Sherbrooke (CHUS) between January 2000 and January 2020. MI incidence during the week following DST transitions was compared to the rest of the year using Poisson regression models, with adjustments for temporal trends, day of the week, and meteorological factors such as mean temperature.
The study found a non-significant 4% increase in MI incidence during the week following the spring DST transition (Incidence Rate Ratio [IRR]: 1.04, 95% CI: 0.93–1.15; p = 0.50) and a non-significant 4% decrease following the fall transition (IRR: 0.96, 95% CI: 0.86–1.08; p = 0.50). While there was numerically more MI in the week following spring transition and less MI following the fall transition, it did not reach statistical significance. Additional analyses examining 1-day, 3-day, and 7-day periods post-DST transitions revealed a similar trend but remained non-significant. Subgroup analyses based on age, gender, and MI type revealed no notable differences. Analyses restricted to data after 2007, accounting for national changes in DST timing and ICD classifications, also demonstrated no significant associations. However, a significant increase in MI incidence was observed on Mondays compared to other days of the week (IRR 1.25, 95% CI: 1.19–1.32; p < 0.001), irrespective of DST, consistent with previous literature highlighting the role of sleep deprivation, stress and chronobiological factors in the pathophysiology of MI.
Conclusion: In this large retrospective single-center study, no significant association was observed between DST transitions and MI incidence. These findings suggest that DST transitions do not represent a substantial cardiovascular risk in the studied population. Future large-scale studies are needed to validate these findings and explore potential broader health impacts of DST in Canada.
