Impact of Daylight Saving Time transition on the internal body clock

Dr Nicole Lovato is Senior Research Fellow at FHMRI: Sleep Health (formerly the Adelaide Institute for Sleep Health) with a research focus on insomnia and circadian rhythms.

“This weekend our clocks turn back by one hour on Sunday morning, with the end of Daylight Saving Time across South Australia, New South Wales, Victoria, Tasmania and the ACT.

An hour extra sleep, that’s got to be a good thing, right?!

Unfortunately, it is not that simple. Changing the clock does not immediately change the timing of our internal body clock, or circadian rhythm.

After the transition off daylight saving time, the circadian rhythm is an hour out of sync, it can feel a bit like mild jetlag. You are likely to feel sleepy earlier than usual (a bonus for parents of young children) and wake up earlier than normal (maybe not such a bonus for parents).

The good news is the mild jetlag will only last 1-2 days as our circadian rhythms delay by an hour to sync with the new standard clock time. This happens easily for most of us.

The body clock has a natural tendency to delay because this internally occurring cycle is slightly longer than 24 hours. For some people, their cycle length can be 25 hours, meaning it will take only one day to sync with the changed clocks.”