Does daylight saving mess with our sleep? It’s complicated
On Sunday, many Australians will set their clocks forward, effectively losing an hour of sleep as we welcome long summer days.
While much has been said and written about the effects of the change on sleep, a new comprehensive analysis from Flinders University suggests the impacts are not long-lasting.
New research suggests the impacts of daylight saving time on sleep are not long-term.Credit: Matt Davidson; iStock
Set to be published later this month, researchers compared the sleep patterns of those in states that observe daylight saving compared to those which don’t.
The analysis, which is yet to be peer-reviewed, found no significant evidence that daylight saving was associated with a loss of sleep, or an impact on sleep quality or daytime functioning.
Researchers used data from two nationwide questionnaires – a representative population sample of 1000 people and a sample of around 700 people with a clinical diagnosis of insomnia – to collect information from the middle and later stages of daylight saving to determine its connection to sleep.
What existing research shows
Given the shift to daylight saving time means a loss of one hour of sleep, it’s inevitable there will be some kind of jet lag effect.
“The literature says that’s a loss of about 40 minutes of sleep on average, and that’s associated with a higher risk of heart attacks and car accidents in the days that follow because of that loss of sleep,” says Yu Sun Bin, a senior lecturer in sleep epidemiology at the University of Sydney.
The change also messes with our circadian rhythm, our invisible body clock that’s attuned to the natural cycle of day and night. Bin says this is compounded by the fact that many people, often referred to as night owls, have a circadian rhythm of longer than 24 hours, meaning the social clock is at odds with our biological clock.
“You’re getting less light in the morning now,” explains Bin. “[So] it’s particularly hard to transition because we’re asking people to do a phase advance, which is rising early and going to bed early.”
Because of this, many sleep experts have advocated for the abolishment of daylight saving time, and such research has informed debates and policies around the practice. In 2019, European Parliament voted to abolish the changing of the clocks, although this has yet to come into effect while in Australia, there have been similar calls to cut back on daylight saving.
What this new research suggests
While previous research has focused on sleep during the immediate transition period to daylight saving, Leon Lack, a sleep expert at Flinders University and lead author of the new study, says this is the first to comprehensively examine potential long-term effects of the change.
Importantly, the study did not pinpoint the period in which these effects subside, which Lack says could happen in a matter of weeks.
“What we do know is we can’t find any evidence of it after two or three months,” he says.
Lack doesn’t deny the effects of daylight savings on our body clocks in the short term, but says these findings put them into perspective. He points to jet lag as an example of the effect of changing time zones, and the fact its impacts are often only short-lived.
Research associate and co-author of the study from the Flinders sleep health team, Reece Kemp, says the biggest implications of the findings is that it “alters the conversation about daylight saving time and removing it”.
Kemp says it’s important to remember that this study is just a snapshot in time. The next steps are for researchers to look more closely at the short-term effect of daylight saving and whether some groups may be more susceptible to its effects than others.
“All we can say is that by the middle to late stages of daylight saving, people’s sleep is comparable to those on standard time throughout the year.”
Bin, who was not involved in the study, agrees the findings add to our understanding of daylight saving and sleep, but says she’d want to see “more objective measures of sleep or of other health outcomes”.
“But those things are really hard to collect.”
How to transition to daylight saving
To navigate the transition to daylight saving and maintain a healthy sleep routine, Lack says it’s important to stick to your regular bedtime and wake-up time.
“In other words, don’t sleep in late, particularly on Sunday morning, but get up early and get exposed to light in the morning.”
Avoiding light after sundown, such as light from phones or overhead lights, is also helpful, says Bin.
Lack says children and teens, who can find it particularly difficult to adjust, should try to stick to their usual school routine (school holidays in Victoria end this weekend, while students return to school in NSW the following week) or risk accruing sleep debt.
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