Springing forward may be hazardous to your health. The Monday following the start of daylight saving time (DST) is a particularly bad one for heart attacks, traffic accidents, workplace injuries and accidental deaths. Now that most Americans have switched their clocks an hour ahead, studies show many will suffer for it.

Most Americans slept about 40 minutes less than normal on Sunday night, according to a 2009 study published in the Journal of Applied Psychology. At least 1.5 billion people across 82 countries observe the tradition, though not all of them adjust their clocks at once, as Quartz reports. Since sleep is important for maintaining the body’s daily performance levels, much of society is broadly feeling the impact of less rest, which can include forgetfulness, impaired memory and a lower sex drive, according to WebMD.

One of the most striking affects of this annual shift: Last year, Colorado researchers reported finding a 25 percent increase in the number of heart attacks that occur on the Monday after DST starts, as compared with a normal Monday. That means hospitals that typically saw about 32 heart attack patients were treating eight additional victims on that day. A cardiologist in Croatia recorded about twice as many heart attacks than expected during that same day, and researchers in Sweden have also witnessed a spike in heart attacks in the week following the time adjustment, particularly among those who were already at risk.

Workplace injuries are more likely to occur on that Monday, too, possibly because workers are more susceptible to a loss of focus due to too little sleep. Researchers at Michigan State University used over 20 years of data from the Mine Safety and Health Administration to determine that three to four more miners than average sustain a work-related injury on the Monday following the start of DST. Those injuries resulted in 2,649 lost days of work, which is a 68 percent increase over the hours lost from injuries on an average day. The team found no effects following the nation’s one-hour shift back to standard time in the fall.

"We think managers and organizations can use this information to help improve safety in the days following the switch to daylight saving time," Christopher Barnes, who is now a management professor at the University of Washington, said in a statement at the time of the study’s release. "They can schedule particularly dangerous work on other days, perhaps later in the week after employees have had more time to adjust their sleep schedules."

There's even more bad news: Drivers are more likely to be in a fatal traffic accident on DST's first Monday, according to a 2001 study in Sleep Medicine. The authors analyzed 21 years of data on fatal traffic accidents in the U.S. and found that, following the start of DST, drivers are in 83.5 accidents as compared with 78.2 on the average Monday. This phenomenon has also been recorded in Canadian drivers and British motorists.

If all that wasn’t enough, a researcher from the University of British Columbia who analyzed three years of data on U.S. fatalities reported that accidental deaths of any kind are more likely in the days following a spring forward. Their 1996 analysis showed a 6.5 percent increase, which meant that about 200 more accidental deaths occurred immediately after the start of DST than would typically occur in a given period of the same length.

Many of these researchers were interested in studying DST as a proxy for the effects of sleep deprivation. Most likely, the lack of sleep that individuals suffer adjusting their clocks is the true culprit in all of these cases. DST simply provides an opportunity for researchers to track its effects across an entire population during the period each year when Americans collectively get less sleep.

Some people say that these risks are an unnecessary part of an arbitrary tradition. A British group called the Campaign for Real Time points to such hazards as the reason that they would prefer to stop changing their clocks twice a year, even though many of the ill effects of a “spring forward” are reversed during the “fall back.” An online petition to abolish DST has gathered about 36,000 signatures, and 5,000 of those have been posted just in the past two days.

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Daylight Saving Time