Daylight saving time, good or bad for your health? If the evenings are longer and sunnier, it nevertheless causes an hour of sleep to be lost, unlike the transition to winter time.
And the time change can be relatively destabilizing: it could indeed be more disturbing for our biological rhythm than the jetlag. And according to a new study published this Wednesday in the magazine Neurology, it would cause an increase in sleep disorders. Researchers from McGill University in Montreal studied the sleep quality of more than 30,000 people between the ages of 45 and 85 after switching to winter time and after switching to summer time.
What were the evaluation criteria? The duration of their sleep, the difficulty in falling asleep, the number of nocturnal awakenings, or the symptoms of drowsiness they may have felt during the day. The participants answered the following questions in particular:In the past month, how often did it take you more than 30 minutes to fall asleep?” And “In the past month, how many times have you woken up in the middle of the night or too early in the morning and had trouble falling back to sleep?“
Short-term disturbances
“Sleep plays an essential role in maintaining good health, mood, cognition, work performance and social activity, and is influenced by the circadian rhythm, the internal clock that regulates bodily processes“, say the researchers.
And after comparing the results between switching to summer time and winter time, the researchers found an increased risk of insomnia in the spring, in particular because the participants had twice as much difficulty fall asleep and had twice as many sleepiness symptoms during the day. “The good news is that these disturbances were brief and disappeared two weeks after the change.remarks Ronald Postuma, author of the study.
The duration of sleep also tended to decrease during the transition to daylight saving time, and ended up being reduced by around 9 minutes. A logical observation, since we would indeed need more sleep in winter, according to a study published in February 2023 in the journal Frontiers in Neuroscience.
Conversely, no change was observed when switching to winter time.
Negative effects already (more or less) known
“The body has a harder time recovering when you put the clock forward than when you put it back, because it’s easier to push back your bedtime than to try to sleep earlier than usual.”confirm to Figaro David Davenne, professor of chronobiology.
“As disruptive as these transitions may seem in the short term, there may be few long-term implications of repeatedly switching from summer to winter time.“, says Prof. Postuma. Nevertheless, the principal researcher acknowledges that the changes towards daylight saving time have been associated with increased risks of stroke and heart attack.
Sources:
- Effects of Season and Daylight Savings Time Shifts on Sleep Symptoms: Canadian Longitudinal Study on Aging, neurologyMay 3, 2023
- How is sleep affected by changing clocks and seasons?, American Academy of NeurologyMay 3, 2023
