A recent study published on May 3, 2023, in Neurology has revealed that the shift from daylight saving time to standard time, which entails gaining an extra hour of sleep, leads to a short-term increase in sleep disorders like difficulty falling or staying asleep. However, no such association was found when transitioning from standard time to daylight saving time, where an hour of sleep is lost. Additionally, the study found a minor variation in the quantity of sleep people obtain depending on the season.
Sleep is crucial for maintaining good health, cognition, mood, job performance, and social activity and is controlled by the circadian rhythm, the body’s internal clock. Ron B. Postuma, MD, MSc, a member of the American Academy of Neurology and a researcher at McGill University in Montreal, Canada, stated, “The good news is that the sleep disturbances observed after the switch to standard time were transitory and disappeared two weeks after the transition.”
The study enlisted 30,097 participants between the ages of 45 and 85, who filled out a questionnaire regarding their sleep habits. The survey aimed to gauge their sleep duration, satisfaction, difficulty falling asleep or staying asleep, and excessive daytime sleepiness. Individuals who reported experiencing any of these problems three or more times per week were classified as having sleep issues.
Regarding the change to standard time in the autumn, researchers analyzed the responses of participants who completed the survey one week before and one week after the shift. After adjusting for factors such as age, gender, and location, the study found that those who responded to the survey one week after the transition had a 34% higher risk of sleep dissatisfaction, with 28% reporting dissatisfaction compared to 23% before the shift. Additionally, participants who responded one week after the transition had a more than two-fold increased risk of having difficulty falling asleep, a 64% increased risk of difficulty remaining asleep, and a two-fold increased risk of experiencing excessive sleepiness during waking hours.
For the transition to daylight saving time in the spring, researchers compared the questionnaire responses of those who filled it out one week before the shift to those who completed it one week after. Although the study found no difference in the prevalence of sleep problems, there was a nine-minute decrease in sleep duration after this transition.
In addition to examining the questionnaire responses before and after the time change, researchers also analyzed when participants completed the survey, either in the spring, summer, fall, or winter. While the study found no difference in sleep problems, there was a small variation in sleep duration.
On average, individuals who completed the questionnaire during the summer had the shortest sleep duration, getting an average of 6.76 hours of sleep per day. Those who completed the survey during the winter had the longest sleep duration, averaging 6.84 hours of sleep per day, a difference of five minutes.
“While the changes caused by daylight saving time transitions may feel disruptive in the short term, there may be little long-term impact,” explained Postuma. However, previous research has linked these transitions to a higher incidence of accidents, as well as an increased risk of stroke and heart attack. Future studies should track individuals over time, including those living in regions with varying light exposure and seasonal fluctuations.
One limitation of the study was that it only involved middle-aged and older adults, and findings may not apply to younger adults.