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When it is daylight savings time, whether it is one hour forward or one hour backwards, people often complain about feeling "thrown off."  In a new study, researchers found that daylight savings do not only disrupt sleeping schedules, they can also negatively affect people's cardiovascular health.

For this study, the researchers examined when heart attacks occurred within the first few weeks after people turned their clocks one hour forward. The team discovered that the number of heart attacks that occurred on the Monday right after daylight savings was 25 percent higher than the incidence rate of heart attacks that occur on any other Monday throughout the year. The team found that during the Monday prior to daylight savings, there were 93 heart attacks. The week after had 125 heart attacks. This trend was noticeable for four straight years.

The data came from the Michigan's BMC2 database, which gathers information on non-federal Michigan hospitals. The database recorded heart attack admissions from Jan. 1 2010 to Sept. 15, 2013. There were 42,060 hospitalizations over the span of 1,354 days.

"What's interesting is that the total number of heart attacks didn't change the week after daylight saving time," said Amneet Sandhu, M.D., cardiology fellow, University of Colorado in Denver, and lead investigator of the study. "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."

The team reported that heart attack cases did not continue to increase throughout the rest of the week. The researchers also noted that heart attacks tend to occur more often during Monday mornings.

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

The study will be presented at the American College of Cardiology's 63rd Annual Scientific Session.