On Sunday, March 10, at 2am, day-light saving time begins. We’ll set our clocks forward one hour, and the change will push sunsets later into the evening hours and sunrises later into the morning. The cost is that “springing forward” will temporarily disrupt the sleep of millions of Americans.
Yet as simple as it seems, there is still a lot of confusion about daylight saving time. The first thing to know: Yes, it begins in the spring, just as the increase in day-light hours starts to become noticeable.
Why are we in daylight saving time now? Why do we need to “save” daylight in the spring? Daylight saving time in the US started as an energy conservation trick during World War I and became a national standard in the 1960s. The big idea is to shift the number of daylight hours we get into the evening. So if the sun sets at 8 pm instead of 7pm, we’d presumably spend less time with the lights on in our homes at night, saving electricity.
Heart attacks spike after the spring time change.
A 2014 study published in Open Heart found a 25% jump in the number of heart attacks occurring the Monday after DST starts, compared to other Mondays during the year. The total number of heart attacks didn’t change for the whole week, though; the burden just shifted to earlier in the week.
It could be that the combined stress of a typical back-to-work Monday and that hour of lost sleep is particularly hard on people who are already vulnerable to heart problems, say the study authors. They also found the opposite to be true in the fall: There was a 21% drop in the number of heart attacks on the Tuesday following the end of DST.
Stroke rates rise when DST starts and ends.
Heart attacks aren’t the only cardiovascular risk associated with changing clocks: Preliminary research presented at the 2016 American Academy of Neurology's annual meeting found that stroke rates in Finland are 8% higher, on average, in the two days following both time changes—spring and fall— compared to the two weeks before or after. Older adults, and people with cancer, seemed to have the most increased risk during this time. Disturbed sleep patterns can contribute to high blood pressure and poor mental health, says Dr. Kumar (who was not involved in the studies mentioned here), both of which are risk factors for heart attack and stroke.
The Journal of Applied Psychology study concluded that workers arrived at work with 40 minutes less sleep and experienced 5.7 percent more workplace injuries in the week directly following the springtime daylight saving transition than during any other days of the year. The researchers attribute the injuries to lack of sleep, which might explain why the same effect did not appear in the fall, when workers gained an hour of sleep.