Modulators of normal bodily functions such as the duration and quality of sleep might transiently influence cardiovascular risk. The transition to daylight savings time (DST) has been associated with a short-term increased incidence of heart attack or acute myocardial infarction (AMI). The present retrospective study examined the incidence of AMIs that presented to Beaumont Hospitals in Michigan the week after DST and after the autumn switch to standard time, October 2006 to April 2012, with specific reference to the AMI type.
The study population (n = 935; 59% men) was obtained from the electronic medical records. Overall, the frequency of AMI was similar in the spring and autumn, 463 (49.5%) and 472 (50.5%), respectively.
The incidence ratio for the first week after the spring shift was 1.17. After the transition from DST in the autumn, the IR for the same period was lower, but not significantly different, 0.99. Nevertheless, the greatest increase in AMI occurred on the first day (Sunday) after the spring shift to DST (1.71, 95% confidence interval 1.09 to 2.02; p <0.05). Also, a significantly greater incidence was found of non–ST-segment myocardial infarction after the transition to DST in the study group compared with that in the control group (p = 0.022). In conclusion, these data suggest that shifts to and from DST might transiently affect the incidence and type of acute cardiac events, albeit modestly.