Permanent daylight time is worse for the body, scientists warn
VANCOUVER - Most North Americans will be turning their clocks back an hour on Sunday to mark the end of daylight saving time. At least for this year, British Columbians will be among them.
But as the provincial government pushes to make daylight time permanent, scientists who study biological rhythms are arguing that we should be abandoning it altogether.
In a position paper first published in June, 10 scientists from the Society for Research on Biological Rhythms argue that standard time -- not daylight time -- should be the permanent choice.
Six of the authors -- all of them researchers at American and European institutions -- elaborated on their position in a Reddit AMA Friday.
"In terms of health, abolishing DST rather than making it permanent is more beneficial," the authors wrote. "Standard time is the time that most closely matches solar time (the sun clock). Research has shown that our body clocks still follow more or less the time of the sun clock. For example, several studies found that the further west people live within a time zone, the more health problems they may experience and the shorter they live on average."
"Using permanent DST would increase the mismatch between our body clock -- which is set by the sun clock -- and the social clock," they continued.
As an example, consider the expected sunrise and sunset times for Vancouver on this year's winter solstice -- the shortest day of the year.
According to Canada's National Research Council, the sun will rise that day -- Dec. 21 -- at 8:05 a.m. and it will set at 4:16 p.m.
Under permanent daylight time, the sun would rise at 9:05 a.m. and set at 5:16 p.m.
While the prospect of leaving the office before the sun goes down may be appealing to some nine-to-five workers, the researchers say it has negative consequences for many people's body clocks.
"The chronic effects may last throughout the months of DST because in many people, social clocks and body clocks remain set to different times," they wrote in their position paper. "The body clock does not adjust to DST social clock time, even over months."
So, under the scenario above, even though clocks in Vancouver might say that it's 9:05 a.m. at sunrise, many people will still feel like it's 8:05 a.m. And, at 9:05 p.m., they'll still feel like it's 8:05 p.m. These people may end up going to bed later during daylight time because their bodies don't feel tired at the time the clock says they should.
In their AMA, the authors characterized this phenomenon as a "drift" in people's biological clocks.
"Morning light is very important for the biological clock to maintain synchrony, and when exposure to morning sunlight is reduced, our biological clocks will drift later and later, making it harder to wake up," they wrote. "At the population level, permanent standard time is the best way to go."