Probably because you're blowing off your chest pains to keep on partying.
Everyone knows that people die on New Year's—which is a buzzkill, I know, but it's true. Half the fatal car crashes on New Year's Day are from drunk drivers, and there's a slight increase in homicides and suicides during the holiday. But January 1 is also the day you're most likely to die of natural causes, according to research by sociologist David Phillips.
Phillips, along with two other researchers, studied 57 million death certificates over a 25-year period. They found a sharp spike in deaths on Christmas, the day after Christmas, and New Year's Day, which has the most fatalities. It's pretty well-documented that substance abuse and accidental fatalities go up during the holidays, but their research showed a spike in natural causes of death—things like cardiac diseases and cancer—more than accidents like drunk driving.
There's no obvious explanation for the pattern. The health problems aren't weather-related, and even if they were, that wouldn't explain the distinct increase during Christmas and New Year's. It's tempting to blame the deaths on stress from visiting with family members or wrapping up end-of-year to-do lists, but the research notes a lack of evidence that "heightened psychological stresses can cause abrupt, sharp increases in mortality from a wide range of diseases and for a wide range of demographic groups." In other words, finding the coolest New Year's party might stress you out, but it's probably not going to kill you.
Stressed about where to party on New Year's Eve this year? THUMP has you covered.
In a recent interview with the Washington Post, Phillips chalked it up to "a mystery," but he did offer a few hypotheses: Most of the Christmas and New Years deaths happen in emergency rooms, which could suggest that people wait longer to seek medical attention during the holidays (because they want to spend time with their families) and are more likely to die by the time they reach the hospital. Alternatively, hospitals might be understaffed during the holidays, meaning you're less likely to make it if you get sent to the ER on New Year's Day.
Either way, if you start feeling weird chest pains on New Year's Day, don't blow it off as a side effect of your hangover.
Follow Arielle Pardes on Twitter.