• The Sound Sleeper

Daylight Saving Time: One hour with a big impact

It’s that time of year again — the second Sunday in March signals the arrival of Daylight Saving Time (DST) and setting our clocks ahead one hour. Losing an hour can be a nuisance, but it’s no big deal, right? Wrong.

A full range of impact

Studies have shown that the switch to DST from Standard Time has led to an increase in traffic accidents, heart attacks, stroke, workplace injuries and suicide in the days following the change. One study found an alarming 24% increase in heart attacks the Monday following the spring time change, while other studies found an 8% increase in stroke risk and a 6% increase in fatal traffic accident risk.

Losing an hour can make you feel groggy, tired, irritable and not quite yourself the next day. You may have trouble making decisions, and find your judgement is impaired, similar to the effects of insomnia. Lack of sleep over the long term can put you at risk of infectious and inflammatory disease as well as mental health issues.

The science behind it

We are guided by a circadian rhythm, a 24-hour cycle that regulates sleep and bodily functions such as appetite and mood. Our biological clock is influenced by natural light exposure, and timing plays an important role: When we are exposed to early morning light, our need to sleep arrives earlier.

The shift to DST means more darkness in the morning and more light in the evening, disrupting the body’s natural rhythm. We end up feeling tired in the morning and alert in the evening, making it harder to go to bed at our regular time and get the quality sleep we need.

Our alertness, mood and energy level can be effected simply by losing sleep that first night. It can take our biological clock a few days to adjust to the new time, and some people find themselves losing sleep for a week or longer. These negative effects threaten our performance at school or work as well as our safety at work and on the road. And the cumulative effect of continuing sleep loss can lead to serious health consequences such as cardiovascular disease, obesity and depression.

Preparation is the key

Many people have no problem adapting to the time change. But if you find that you tend to struggle with it, or want to perform at your best Monday morning, there are ways to prepare:

  • Starting a few days before the time change, go to bed 15 to 20 minutes earlier each night.
  • Adjust your daily routines in the same way — for example, eat dinner a little earlier each night.
  • On the Saturday night of the change, set your clock ahead in the early evening, and resume your normal bedtime.
  • Avoid exposure to electronic devices before bedtime (good year-round advice!).
  • On Sunday morning, take a walk or simply go outside and get sun exposure to help regulate your internal clock.
  • Go to bed at your normal time Sunday evening to be ready for your week.

Sources: David Robb, et al. (2018) Accident Analysis & Prevention; Roberto Manfredini, et al. (2019) Journal of Clinical Medicine; Jussi O T Sipilä, et al. (2016) Sleep Medicine; Christopher M. Barnes, et al. (2009) Journal of Applied Psychology; Michael Berk, et al. (2008) Sleep and Biological Rhythms; Amneet Sandhu, et al. (2014) Open Heart; American Academy of Neurology; Josef Fritz, et al. (2020) Current Biology; American Academy of Sleep Medicine; Kimberly Honn, et al. (2020) Sleep Research Society; Sleep Foundation

The American Academy of Sleep Medicine found that 55% of people surveyed felt extremely or somewhat tired after the spring change to Daylight Savings Time.

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