As the main potential explanation for the observed findings, DST transition may cause a disruption of the circadian rhythm, which in turn induces changes in sleep quantity and quality [24], together with a predominance of sympathetic activity, an increase in pro-inflammatory cytokine levels and a rise in heart rate and blood pressure [25,26]. Acting together, these factors have already been recognized as possible triggers of an increased cardiovascular risk following DST shifts [27,28]. Interestingly, although a misalignment between the internal circadian clock and the exogenous clocks should happen after both shifts [29], it has been suggested that the spring transition may be more disruptive on the circadian rhythm than the autumn transition [30,31], because turning the clocks forward induces one-hour shortening of the day and a likely sleep reduction [32,33].

#1
Daylight savings time and myocardial infarction
Conclusion
Increased rates of AMI requiring PCI were identified on the Monday following the spring DST change. Decreased rates of AMI requiring PCI were identified on the Tuesday following the fall DST time change. No change in the total volume of PCI for AMI was seen in the weeks preceding or following either DST time change. Further work exploring the impact of these findings on cardiovascular care should be considered.

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#2
Daylight Saving Time and Acute Myocardial Infarction: A Meta-Analysis
Conclusion
This meta-analysis showed a modest but significant increase in the risk of AMI following DST transitions, that was particularly noticeable after the spring DST shift. Overall, these findings support the proposal of a DST transition discontinuation, although additional evidence is certainly needed to confirm the present results, identify high-risk subjects and quantify the relationship between DST transition and other severe diseases.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4189320/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6463000/