‘Circadian Assaults’: Daylight Saving Time May Hasten Strokes, MIs in Those At Risk

Philippe Boulet/flickr creative commons

I don’t like daylight saving time (DST). Twice a year, when we begin and end this transition, I’m tired and cranky for a week. These sudden leaps forward and backward in time disrupt our bodies’ natural relationship to what should be gradual changes of season.

Not surprisingly, some studies suggest that these assaults on our circadian rhythms may affect our cardiovascular health. Swedish studies (here and here) based on national myocardial infarction (MI) data found small but significant increases in MI rates in the first few days to a week after the change to DST.

A Michigan study of more than 42,000 MI patients treated with angioplasty found a significant increase in MIs on the Monday after the start of DST. Their data, however, indicated that the overall incidence rate of MIs in need of angioplasty did not change, and the researchers suggested that DST may simply “accelerate” the incidence of cardiovascular events in at-risk patients, pulling them forward in time.

Researchers in Finland recently reported an increase in strokes at the start of DST, and like the Michigan researchers, concluded from their data that this was an acceleration of stroke events in vulnerable people rather than an overall increase in incidence.

A key underlying factor in this DST-related increase in cardiovascular events appears to be sleep loss. The authors of the Swedish studies noted that “daylight saving time shifts can be looked upon as large-scale natural experiments to study the effects of acute minor sleep deprivation and circadian rhythm disturbances.”

Nurses and other shift workers may be particularly vulnerable to the problems that can result from sleep deprivation. For a discussion of how sleep loss affects nurses, see “The Potential Effects of Sleep Loss on a Nurse’s Health” in our April 2015 issue.