Scientists who study sleep are warning B.C.’s decision to adopt permanent daylight time could have a negative impact on overall health, especially for children.
“Scientists over the world have been warning about the negative health and safety implications of permanent daylight saving time and have been advocating for permanent standard time instead,” said Myriam Juda, an adjunct professor and sleep researcher at Simon Fraser University.
The change means B.C. will transition onto daylight time this weekend and never change the clocks again.
Among the critics is Jamie Zeitzer, a professor in Stanford University’s department of psychiatry and behavioral sciences, whose research was cited by the B.C. government in its news release announcing the change.
Zeitzer says it was “kind of weird” to see his work used that way.
“It’s scientifically not a good idea, and in terms of health, I don’t think it’s a good idea to do that kind of switch,” he said.
What the science says
Standard time means the sun is at its zenith around noon, with daylight more evenly split between morning and afternoon. Daylight saving time shifts the clock ahead by an hour, meaning less light in the morning and more in the afternoon.
Juda said that change can disrupt our circadian clock, which regulates sleep-wake cycles.
“This circadian clock synchronizes to the light-dark cycle of the sun through specialized photoreceptors in the eye. And morning light exposure is really important here,” she said.
Morning light helps set the timing of melatonin release later in the day. Without it, people may feel more alert at night and more fatigued during the day, Juda said. She added that teenagers are particularly affected because their sleep patterns already tend to shift later.
Sleep is also critical for children’s brain development, she said.
Communities on the western edge of a time zone, such as Vancouver and Victoria, are especially affected by dark winter mornings under permanent daylight time. In midwinter, the shift would push sunrise past 9 a.m. in both cities.
“That means that most children will walk to school in the dark. Most office workers will commute in the dark and also will not get an opportunity for any morning light exposure,” Juda said.
She estimates most British Columbians would lose, on average, just under half an hour of sleep each night after the change.
Daylight time can also contribute to “social jet lag,” when daily schedules are misaligned with the body’s preferred light exposure. In the short term, this could mean people feel groggy or sluggish. Over time, that mismatch — combined with less sleep — can snowball into other health problems.
Zeitzer said modelling by his team in the U.S. linked an out-of-sync circadian cycle to a range of poor health outcomes.
“Basically, being in permanent standard time — from a circadian perspective — is going to be healthier, especially when it comes to strokes and obesity, than switching over to permanent daylight time,” he said.
None of the scientists interviewed by CBC said they were aware of peer-reviewed health research supporting a switch to permanent daylight saving time.
However, Zeitzer said his team’s research also suggests ending the twice-yearly clock changes is better than keeping them. He said the spring time change — but not the fall one — is associated with higher rates of heart attacks and car crashes as people adjust to less sleep after moving their clock forward an hour.
Public support, limited options
The extra evening daylight on permanent daylight time will have benefits in terms of more time for outdoor activity and safer commutes, the B.C. Ministry of Attorney General said in an emailed statement.
“Concentrating limited winter daylight at the end of the day aligns better with when most people are active, which could help reduce collisions and improve overall well‑being.”
The government cited more than 90 per cent support for permanent daylight saving time during public consultations in 2019.
But British Columbians were offered only two choices: Keep changing the clocks or switch to permanent daylight saving time. Other options — such as permanent standard time — were not considered.
“That’s not really a valid choice,” Zeitzer said. “It’s like saying … am I doing a great job as a teacher or a fantastic job as a teacher?”
The government said standard time was not offered as an option because none of B.C.’s neighbouring jurisdictions were considering a move to permanent standard.
“We wanted to ensure that whatever decision we made would be done in a manner that maintained alignment with these jurisdictions. As such, we did not consider a move to standard time to be a viable option.”
The ministry did not respond to a question about which scientific sources were consulted to inform the decision to choose daylight time.
Zeitzer said there may be economic reasons that some favour daylight saving time, including longer, lighter evenings.
“People will go play golf, and they’ll go shopping and dining, and otherwise they wouldn’t do that if it was already dark out. And frankly, if the argument is that that is going to make wealthy people wealthier, I don’t think that impacts health,” he said.
But if there was evidence people who work at these places have jobs they otherwise wouldn’t and their income goes up, there could be health arguments there, he said.
“But they have not really been well laid out.”
