In this task, you are given a text of many news articles seperated by special token "|||||". Your task is to summarize them.

WASHINGTON Switching over to daylight saving time, and losing one hour of sleep, raised the risk of having a heart attack the following Monday by 25 percent, compared to other Mondays during the year, according to a new U.S. study released on Saturday. 
  
 By contrast, heart attack risk fell 21 percent later in the year, on the Tuesday after the clock was returned to standard time, and people got an extra hour's sleep. 
  
 The not-so-subtle impact of moving the clock forward and backward was seen in a comparison of hospital admissions from a database of non-federal Michigan hospitals. It examined admissions before the start of daylight saving time and the Monday immediately after, for four consecutive years. 
  
 In general, heart attacks historically occur most often on Monday mornings, maybe due to the stress of starting a new work week and inherent changes in our sleep-wake cycle, said Dr. Amneet Sandhu, a cardiology fellow at the University of Colorado in Denver who led the study. 
  
 "With daylight saving time, all of this is compounded by one less hour of sleep," said Sandhu, who presented his findings at the annual scientific sessions of the American College of Cardiology in Washington. 
  
 A link between lack of sleep and heart attacks has been seen in previous studies. But Sandhu said experts still don't have a clear understanding of why people are so sensitive to sleep-wake cycles. 
  
 "Our study suggests that sudden, even small changes in sleep could have detrimental effects," he said. 
  
 Sandhu examined about 42,000 hospital admissions in Michigan, and found that an average of 32 patients had heart attacks on any given Monday. But on the Monday immediately after springing the clock forward, there were an average of eight additional heart attacks, he said. 
  
 The overall number of heart attacks for the full week after daylight saving time didn't change, just the number on that first Monday. The number then dropped off the other days of the week. 
  
 People who are already vulnerable to heart disease may be at greater risk right after sudden time changes, said Sandhu, who added that hospital staffing should perhaps be increased on the Monday after clocks are set forward. 
  
 "If we can identify days when there may be surges in heart attacks, we can be ready to better care for our patients," he said. 
  
 The clock typically moves ahead in the spring, so that evenings have more daylight and mornings have less, and returns to standard time in the fall. Daylight saving time was widely adopted during World War I to save energy, but some critics have questioned whether it really does so and whether it is still needed. 
  
 Researchers cited limitations to the study, noting it was restricted to one state and heart attacks that required artery-opening procedures, such as stents. The study therefore excluded patients who died prior to hospital admission or intervention. 
  
 (Reporting by Ransdell Pierson; Editing by James Dalgleish) ||||| Still feeling the residual effects of springing ahead for daylight saving time? The hour of sleep lost - or gained - may play a bigger, perhaps more dangerous role in our body's natural rhythm than we think. It seems moving the clock forward or backward may alter the timing of when heart attacks occur in the week following these time changes, according to research to be presented at the American College of Cardiology's 63rd Annual Scientific Session. 
  
 Data from the largest study of its kind in the U.S. reveal a 25 percent jump in the number of heart attacks occurring the Monday after we "spring forward" compared to other Mondays during the year - a trend that remained even after accounting for seasonal variations in these events. But the study showed the opposite effect is also true. Researchers found a 21 percent drop in the number of heart attacks on the Tuesday after returning to standard time in the fall when we gain an hour back. 
  
 "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." 
  
 Heart attacks historically occur most often on Monday mornings. Sandhu explains that in looking at other "normal" Mondays, there is some variation in events, but it is not significant. However, when he and his team compared admissions from a database of non-federal Michigan hospitals the Monday before the start of daylight saving time and the Monday immediately after for four consecutive years, they found a consistent 34 percent increase in heart attacks from one week to the next (93 heart attacks the Monday before compared to 125 the week after the start of daylight saving time for the duration of the study.). 
  
 Although researchers cannot say what might be driving the shift in heart attack timing after the start of daylight saving time, they have a theory. 
  
 "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. "With daylight saving time, all of this is compounded by one less hour of sleep. Whatever the reason, he said, the findings may indicate a need to better staff hospitals the Monday after setting our 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. Gaining an hour in the fall may have the opposite effect, though authors don't know why there were fewer heart attacks on Tuesday rather than Monday. 
  
 Researchers used Michigan's BMC2 database, which collects data from all non-federal hospitals across the state, to identify admissions for heart attacks requiring percutaneous coronary intervention from Jan. 1, 2010 through Sept. 15, 2013. A total of 42,060 hospital admissions occurring over 1,354 days were included in the analysis. Total daily admissions were adjusted for seasonal and weekday variation, as the rate of heart attacks peaks in the winter and is lowest in the summer and is also greater on Mondays and lower over the weekend. 
  
 The hospitals included in this study admit an average of 32 patients having a heart attack on any given Monday. But on the Monday immediately after springing ahead there were on average an additional eight heart attacks. There was no difference in the total weekly number of percutaneous coronary interventions performed for either the fall or spring time changes compared to the weeks before and after the time change. 
  
 This study comes amid ongoing debate about whether daylight saving time is actually needed anymore. Widely implemented during World War I, it was primarily adopted to save energy. But some experts question whether it really saves energy and if it has negative health effects beyond just leaving us feeling groggy and out of sorts. 
  
 "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." 
  
 There are limitations to the study. For example, it was restricted to one state and heart attacks necessitating percutaneous coronary intervention, therefore excluding patients who died prior to hospital admission or intervention. 
  
 Sandhu said it would be interesting to compare these findings against heart attack trends in Hawaii and Arizona, which do not have daylight saving time. Future research is also needed to better understand 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. 
  
 This study will be simultaneously published online in Open Heart at the time of presentation. 
  
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 The ACC's Annual Scientific Session brings together cardiologists and cardiovascular specialists from around the world each year to share the newest discoveries in treatment and prevention. Follow @ACCMediaCenter and #ACC14 for the latest news from the meeting. 
  
 The American College of Cardiology is a nonprofit medical society comprised of 47,000 physicians, surgeons, nurses, physician assistants, pharmacists and practice managers. The College is dedicated to transforming cardiovascular care, improving heart health and advancing quality improvement, patient-centered care, payment innovation and professionalism. The ACC also leads the formulation of important cardiovascular health policy, standards and guidelines. It bestows credentials upon cardiovascular specialists, provides professional education, supports and disseminates cardiovascular research, and operates national registries to measure and promote quality care. For more information, visit CardioSource.org. 
  
 Sandhu will present the study, "The Impact of Daylight Savings Time on the Timing and Incidence of Patients Undergoing Percutaneous Coronary Intervention for Acute Myocardial Infarction," on Saturday, March 29 at 9:30 a.m. EDT in Hall C. |||||
If you've got a weak heart, you might have a good excuse for taking Monday off next time clocks go forward in spring, researchers say. A new study finds that the daylight saving time switch is associated with a shocking 25% rise in the risk of heart attacks on the following Monday compared to other Mondays in the year, Reuters reports. The effect—much greater than estimated in previous studies—is reversed when clocks go back in fall and people get an extra hour of sleep, the study finds. Mondays are already the worst day of the week for heart attacks, notes the lead researcher, who studied years of admissions data from Michigan hospitals. "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," he says in a press release. "With daylight saving time, all of this is compounded by one less hour of sleep." He says that in light of the study, hospitals should aim to have extra staff on hand the Monday after the clocks change.