Daylight Saving Time
March 31, 2014

Spring Forward: Heart Attacks More Numerous After Daylight Saving Time In The Spring

Brett Smith for - Your Universe Online

Daylight saving time – some people love it and some hate it.

Those who dislike losing an hour of sleep once a year may have a strong argument against daylight saving time as a new study has found an increase in heart attacks is linked to the Monday after we “spring ahead.”

According to the report, which was presented at the American College of Cardiology's 63rd Annual Scientific Sessions in Washington, DC and published online in the journal Open Heart, Michigan-based researchers observed a 25 percent jump in the quantity of heart attacks the Monday after clocks in the state are moved ahead one hour, as opposed to other Mondays during the year. The study also showed the opposite effect – with a 21 percent drop in the amount of heart attacks on the Tuesday after Michiganders turn their clocks an hour back in the fall.

"What's interesting is that the total number of heart attacks didn't change the week after daylight saving time," said lead investigator Dr. Amneet Sandhu, cardiology fellow at the University of Colorado in Denver. "But these events were much more frequent the Monday after the spring time change and then tapered off over the other days of the week. It may mean that people who are already vulnerable to heart disease may be at greater risk right after sudden time changes."

While most heart attacks occur on a Monday, study researchers found a steady 34 percent rise in heart attacks from one week to the next when looking at admissions to non-federal Michigan hospitals the Monday prior to the start of daylight saving time and the Monday right after for four consecutive years.

"Perhaps the reason we see more heart attacks on Monday mornings is a combination of factors, including the stress of starting a new work week and inherent changes in our sleep-wake cycle," Sandhu said.

He added that the findings may point to a need for better staffing at hospitals the Monday after setting clocks forward.

"If we can identify days when there may be surges in heart attacks, we can be ready to better care for our patients," said Sandhu.

The hospitals incorporated into the study, which were pulled from Michigan's BMC2 database, reported an average of 32 admissions with a heart attack on any given Monday. However, on the Monday following moving the clocks ahead, there were on average eight more heart attacks than normal.

Widely adopted in the western world, daylight saving time is the practice of moving clocks ahead during the spring to allow for evening hours to have more light than morning hours. It was initially adopted during World War I to save energy, but there has been some recent debate about how much energy the practice actually saves.

"We go through daylight saving time periods twice yearly," Sandhu said. "We may want to look more closely at whether the shift in the timing of heart attacks seen after daylight saving time leads to any negative health outcomes."

The doctor said it would be useful to check these conclusions against trends in Hawaii and Arizona, which do not have daylight saving time. He also called for research to better comprehend the role of our circadian rhythms on heart health.

"We know from previous studies that a lack of sleep can trigger heart attacks, but we don't have a good understanding of why people are so sensitive to changes in sleep-wake cycles. Our study suggests that sudden, even small changes in sleep could have detrimental effects," he said.


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