For people in poor health, especially those with heart-related challenges such as high blood pressure, an annual rite of spring -- the changeover to daylight saving time in March -- can be a dangerous time.
For two or three days after clocks are moved forward an hour, the risk of having a stroke or heart attack goes up. A Finnish study found that the incidence of stroke goes up by 8 percent, while Swedish researchers found that people are at a 6.7 percent greater risk of heart attack.
Even more alarming were the results of a U.S. study that found heart attack risk shot up by 24 percent on the Monday after we switch to daylight saving time. “The heart has a pretty significant circadian rhythm,” explains sleep expert Dr. Chris Winter, adding that this lost hour makes people vulnerable, "not causing a heart attack but perhaps exacerbating underlying conditions.”
Spring forward, fall back:
- The same U.S. study found that heart attack risk fell 21 by percent on the Tuesday after the fall time change, when clocks return to normal. The effects of daylight saving time on the human body have been likened to jet lag.
- Hawaii, Arizona, and Navajo Nation communities don’t change their clocks twice a year. Other states, such as California and Florida, are hoping to stop the practice legislatively.
- The United States formally adopted the clock-manipulating practice in 1918. It was hoped that consumers would take advantage of the extra sunshine and go shopping, or just spend more time outdoors.