Association of daylight saving time transitions with incidence and in-hospital mortality of myocardial infarction in Finland

Introduction Circadian rhythm disturbance increases cardiovascular risk but the effects of daylight saving time (DST) transitions on the risk of myocardial infarction (MI) are unclear.

Methods We studied association of DST transitions in 2001–2009 with incidence and in-hospital mortality of MI admissions nationwide in Finland. Incidence rations (IR) of observed incidences on seven days following DST transition were compared to expected incidences.

Results Incidence of MI increased on Wednesday (IR 1.16; CI 1.01–1.34) after spring transition (6298 patients’ cohort). After autumn transition (8161 patients’ cohort), MI incidence decreased on Monday (IR 0.85; CI 0.74–0.97) but increased on Thursday (IR 1.15; CI 1.02–1.30). The overall incidence of MI during the week after each DST transition did not differ from control weeks. Patient age or gender, type of MI or in-hospital mortality were not associated with transitions. Renal insufficiency was more common among MI patients after spring transition (OR 1.81; CI 1.06–3.09; p?p?=?0.007), but more common after autumn transition (OR 1.21; 1.00–1.46; p?Conclusions DST transitions are followed by changes in the temporal pattern but not the overall rate of MI incidence. Comorbidities may modulate the effects DST transitions.

• KEY MESSAGES

• Both spring and autumn daylight saving time transitions changed the temporal occurrence pattern but not the overall incidence of myocardial infarction occurrence on the week following the clock shift.

• The age or gender distribution of patients, ratio of different types of myocardial infarctions or in-hospital mortality were not affected by clock shifts.

• The effect of daylight saving time transitions on MI incidence may be modified by the presence of diabetes.