Daylight Savings Time Tied to Heart Attacks

Heart attack rates rose after spring time change and decreased after fall time change

/ Author:  / Reviewed by: Joseph V. Madia, MD Beth Bolt, RPh

(RxWiki News) It can be tough to wake up that first spring morning after "losing an hour" with daylight savings time, but could it also be harmful to your health? A new study explored that possibility.

This study looked at rates of heart attacks in the state of Michigan following daylight savings time changes.

The study found an increase in heart attacks the day following the spring time change, and a decrease in heart attacks following the fall time change.

"Try to go to bed at the same time each day to help regulate your sleep cycle."

According to the authors of this study, led by Amneet Sandhu, MD, of the Department of Internal Medicine at The University of Colorado in Denver, limited earlier research has suggested an increase of heart attacks after clocks "spring forward" an hour in the spring, and a decrease after clocks "fall back" to normal time during fall.

Dr. Sandhu and team set out to explore the potential connection between daylight savings time clock changes and heart attack rates. To do so, they used data from the Blue Cross Blue Shield of Michigan Cardiovascular Consortium database, which gathered data from health care centers across the state of Michigan.

The researchers identified cases of heart attack between March 2010 and September 2013. The data was analyzed to look for differences in the weeks after the spring and fall time changes.

Over this time period, 42,060 heart attacks were identified. The average daily heart attack count was 31, with daily rates ranging from a low of 14 to a high of 53.

After adjusting the data for seasonal trends in heart attacks, Dr. Sandhu and team found that the Monday following the "spring forward" time change was associated with a 24 percent increase in the daily heart attack count. The researchers also found that the Tuesday following the "fall back" time change was associated with a 21 percent decrease in the daily heart attack count.

These changes accounted for an expected increase of 7.8 heart attacks on the day after the spring time change, and an expected decrease of 7.1 heart attacks on the day after the fall time change.

In looking at the weeks following time changes as a whole, the researchers didn't find any significant changes in the overall weekly volume of heart attacks following either time change.

Dr. Sandhu and team explained that their findings suggest daylight savings time might accelerate heart attacks that were already likely to occur among vulnerable patients, but not that daylight savings affects the overall heart attack rate.

It is important to note that the database used in this study identified heart attacks by looking for instances of percutaneous coronary intervention, which the study authors said is the main method of heart attack treatment. Therefore, heart attacks that were treated in another manner, or perhaps not treated at all, were not included in this study. Also, Mondays throughout the year often see a spike in heart attacks when compared to other days of the week.

"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," said Dr. Sandhu in a press release from the American College of Cardiology. "With daylight saving time, all of this is compounded by one less hour of sleep."

Further research is needed to confirm these findings among a wider population beyond the state of Michigan.

This study was published online March 30 in the journal Open Heart. No conflicts of interest were reported.

Review Date: 
April 2, 2014
Last Updated:
April 3, 2014