Strokes, diet and Google: Odd side effects of daylight saving revealed

Will Sunday see a spike in heart attacks? Or car crashes? And why do our Google searches change? It turns out daylight saving time has some bizarre effects. We sort fact from fiction.

When the clocks move forward an hour on Sunday morning, the impact can be far greater than just losing some shut eye, experts have revealed.

Our biological clock cannot adjust to the shift as quickly as our watches, and this can have wide-ranging impacts from heart attack rates to the Google searches of office workers.

Epidemiologist and Sydney University Charles Perkins Centre’s Sleep Group research fellow Dr Yu Sun Bin said our body clocks were “attuned to that cycle of day and night” and we then forced them to “jump”.

“We’re assuming the body can make a change of one hour in a day, instantaneously,” she said.

“That’s not the case at all.”

She said it was a bit like jet lag except, unlike when landing in a new time zone, the cues our bodies normally rely on to stay on time – like sunset and sunrise – will not help.

“This is the opposite, where the cues are remaining the same,” she said.

Clocks will move forward an hour on Sunday morning.

She said multiple studies had found heart attacks increased the day after the time change by about 5 per cent – regardless of whether the clock moved forward or backward.

“Then there is evidence that there is a similar sort of size increase in the risk of stroke as well in the first couple of days after the transition,” she said.

She said the loss of sleep and the disruption to our schedule, regardless of hours slept, could both play a role.

“It’s both the loss of sleep is something that is supposed to affect hypertension and cardiovascular health and puts your body at slightly higher stress the next day” she said.

“That contributes to heart attacks and strokes the next day in people who probably were a bit borderline, and then having the stress of that lost sleep probably just puts them over the edge.

“The other element is the circadian disruption.

“Rhythms throughout the body are desynchronised from what we would like to be doing, so for example we’re probably eating an hour earlier than we’re used to, we’re going to work an hour earlier.”

Multiple studies have found heart attacks increased the day after a time change.

She said this disruption, which essentially means various background or automatic processes by our body – such as the release of hormones that make us sleepy – can be out of sync, and also had other impacts.

“That increases other negative health outcomes like driving a poor mood,” she said.

She said this could impact people with mental health disorders, with some evidence showing the shift could trigger episodes for people living with bipolar disorder.

“There’s some studies suggesting the risk of suicide increases in the couple of days after the transition to daylight saving, but because suicide is such a rare event luckily our confidence in that [conclusion] isn’t high … it’s hard to control for other variables”.

She said the loss of sleep also impacted work, and an analysis of Google search data had once found a spike in entertainment searches during work hours compared to other days.

“We know when people lose sleep … there’s a loss of productivity, or being at work but mentally absent,” she said.

“There are studies in the US which suggest that there are more workplace injuries . . and that those injuries are actually more severe.”

Daylight saving also presents a sleep schedule nightmare for parents.

Fellow Charles Perkins Centre health expert and “Healthy Parents, Healthy Kids” author Dr Nicholas Fuller said we might also see changes in our diet.

“The one hour less sleep we get often has a flow on effect to our lifestyle choices the next day,” she said.

“Research shows that one night of sleep deprivation (less than seven hours of sleep) results in an increase in our hunger hormone, ghrelin.

“You wake up feeling hungrier and you’re more likely to make poor diet choices.”

A spike in car crashes had been a popular claim of daylight saving, but Dr Bin said this claim was actually not clear cut.

“There are some studies that say there’s an increase in car accidents, and others that say there’s no change, and others that say, actually it’s a bit safer,” she said.

She said she suspected a region’s distance to the equator played a role – and whether the shift in daylight hours led to more, less or the same number of car trips taking place in the dark.

But regardless of what changes occur, they will not be forever.

You may wake up feeling hungrier than normal.

Dr Bin said the heart attack and stroke risks were elevated in the initial 48 hours, while the impact on sleep tended to last about a week.

“(After a week), we’ve got used to behaving at a particular time according to the clock,” she said.

Flinders University sleep expert Professor Leon Lack said his research, comparing questionnaires from the middle and end of the daylight saving time period, did not find lasting health impacts.

“We found that those who live in states that observe DST tended to go to bed and wake up later compared to those in regions that stay on standard time,” he said.

“Importantly, the study found no significant evidence that DST was associated with a loss in overall sleep duration or a negative impact on sleep, sleep health, or daytime functioning during the latter part of the DST period.”

Dr Bin said anyone who struggled with the initial transition should try and get light early in the day – and less at night – to help adjust their body clock.

Originally published as Strokes, diet and Google: Odd side effects of daylight saving revealed