5 daylight time facts that will open your eyes
Semi-annual 1-hour change linked to increase in heart attacks, more traffic fatalities
By Jon Hembrey, CBC News
Posted: Mar 8, 2013 3:26 AM MT
Last Updated: Mar 8, 2013 8:52 AM MT
Most Canadians will be moving their clocks an hour ahead on Sunday, March 10 for the switch to daylight time, and many will wake up bleary-eyed and drowsy, because of a slightly shorter rest.
But take heart: the missing hour will mean a longer sleep when the clocks go back on Nov. 3. The time changes are scheduled for 2 a.m. to create the minimal amount of disruption to daily life. It is commonly called daylight saving time.
A quote often attributed to Winston Churchill, a man known for his oratorical prowess, says we pay back the loan of an extra yawn in spring with the “golden interest” of a lengthier snooze in the autumn.
Daylight time, which was first enacted in Germany during the First World War to save energy, aims to take advantage of daylight hours by pushing the clocks ahead in the spring so people don’t sleep through the first few hours of sunshine.
Although the shift of only one hour seems fairly innocuous, the semi-annual clock change has been linked to some surprising effects on things such as health and traffic safety. Here are five interesting facts about daylight time.
Daylight time and heart attacks
A Swedish study published in the New England Journal of Medicine in 2008 found a higher incidence of heart attacks — approximately a seven per cent increase — in the first three weekdays after the clocks spring forward, which researchers attributed to a lack of sleep.
They also noted a similar decrease when the clocks fall back in the fall. The information was based on Swedish records collected over a 20-year period.
"The most plausible explanation for our findings is the adverse effect of sleep deprivation on cardiovascular health,” the researchers wrote.
Another study, this time from two researchers at Carnegie Mellon University in Pittsburgh, found that daylight time has a significant impact on the number of pedestrians killed by vehicles in the immediate aftermath of the switch.
People walking during rush hour in the first few weeks after the clocks fall back in the autumn were more than three times as likely to be fatally struck by cars than before the change. There was no significant difference at noon, but there was around 6 p.m.
The researchers, who looked at seven years of U.S. traffic statistics, also found there was a decrease in deaths when clocks spring forward.
It isn’t the darkness per se that increases the number of deaths in the fall, the researchers suggested. Rather, it's that drivers and pedestrians have spent the previous months getting used to the light conditions, and don’t immediately adjust their behaviours to account for less of it during rush hour.
Daylight time and insomniacs
Although most people are able to adjust to the biologically earlier schedule after March 10, those who suffer from sleep disorders have a much harder time, according to Judith Davidson, an adjunct assistant professor at Queen’s University in Kingston, Ont.People suffering from insomnia often have a much harder time getting used to the time change. (iStock)
Much of the treatment of insomnia involves getting people onto a regular sleep schedule, and the time change can throw that off, she said.
“They always take a long time to fall asleep, but it’s a bit accentuated by the spring time-change,” said Davidson, who treats people for insomnia at the Kingston Family Health Centre.
That can mean several days or even a week of poor sleep for those suffering from insomnia.
Many places don’t use it
Daylight time isn't used everywhere in the world. Saskatchewan and some parts of B.C. don’t use it, for example, nor do Arizona and Hawaii in the U.S.
It is unnecessary at or near the equator, because the length of each day remains the same or varies by just a small amount.
The vast majority of countries in Africa and Asia don’t use daylight saving time.
Fall back and time paradoxes?
Apart from messing with sleep cycles, daylight saving can create some downright unusual situations. Last year, an Ohio man was arrested for drinking and driving twice at the same time on the same day by the exact same police officer.
While it recalls Groundhog Day, the 1993 comedy starring Bill Murray about a man who keeps reliving the same day, it's actually a case of simple math.
The Ohio man was arrested at 1:08 a.m. on Nov. 4, 2012, taken to the police station and released a short time later. However, at 2 a.m. that morning, the clocks were set back to 1 a.m.
The man was arrested exactly one hour after his initial booking by the same officer, again for drinking and driving.
The time was 1:08 a.m.
His blood-alcohol level, however, was slightly lower.
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