Does Daylight Saving Time Really Harm Your Sleep-Wake Cycle?

Patient Expert

Daylight saving time (DST) is used in roughly 70 countries around the world. Moving the clocks forward by one hour is intended to better match daylight hours with human activity.

Whether or not DST is a good idea is open for debate and generates a lot of discussion every year.

Some studies have found that the additional daylight resulting from DST reduces car accidents and pedestrian fatalities. Other studies have blamed DST on an increased risk of accidental death.

It makes sense to assume that setting the clocks forward by one hour (and the subsequent loss of an hour of sleep) would have a negative effect on our sleep-wake cycle. But is that really the case?

How DST affects sleep

A study published in the Journal of Circadian Rhythms set out to determine how the switch to DST affects our circadian rhythm. Some of the results were quite surprising.

Participants in the study wore accelerometers on their wrists to measure rest and activity cycles over a 10-day period during which the clocks changed due to DST.

In addition to measuring rest and activity with the accelerometers, participants were asked to complete a Morningness-Eveningness Questionnaire. This questionnaire is used to identify whether someone is a morning person, an intermediate (daytime) person, or an evening person based on their preference for daily activity patterns.

Researchers found that the transition into DST had no significant effect on the rest-activity cycle of participants. The authors of the study expected to see the transition into DTS weaken the circadian rhythm and push individuals into a later activity phase, but that did not happen.

Who is most affected?

The clock change did have some minor effects on some participants. Individuals who reported preferring to sleep for eight hours or less experienced more fragmentation of their rest-activity cycle, while those who preferred sleeping for longer than eight hours experienced less fragmentation of their rest-activity cycle. As the authors of the study point out, this suggests that **long-sleepers gain from DST, whereas short-sleepers tend to lose out. Study data also revealed that morning people found it easier to cope with the shorter circadian period, while evening people were more likely to be negatively affected by the shortening of the day.

The research found that women and younger individuals were better at reacting to the clock change compared to men and older individuals.

Interestingly, researchers found that the rest-activity cycle disruptions of those who were affected by the clock change lasted for just four days.

Make the transition easier

If you find the DST transition difficult, try going to bed an extra 15 minutes earlier each night from the Wednesday prior to daylight saving. For example, if you normally go to bed at 11 p.m., go to bed at 10:45 p.m. on Wednesday night. On Thursday night, go to bed at 10.30 p.m., on Friday night go to bed at 10.15 p.m., and on Saturday night go to bed at 10 p.m. Consider eating your evening meal an hour earlier than normal on Saturday, too.

Making small changes to your sleep over the course of a few nights should be relatively easy for your body to adjust to. Then, when DST hits, you won't actually be losing any sleep since you went to bed an hour earlier than normal.

When you wake on Sunday morning, spend plenty of time outdoors in order to exposure yourself to natural light. This will help reset your internal body clock.

Finally, make sure you go to bed at your normal bedtime on Sunday night, so that you'll be able to rise at your normal wake time on Monday morning.

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