As the fall months progress, I get excited for what’s to come—beautiful fall colours, crisp mornings, and anything pumpkin spice. But fall season also signals the end of daylight saving time—DST is the practice of moving clocks forward one hour in spring (spring forward) and back one hour in the fall (fall back). This practice was intended to make better use of natural daylight by shifting an hour of daylight from the early morning to the evening during the warmer months.
While it may seem like a small matter, this one-hour shift can throw off our body’s internal clock and disrupt sleep. In the days after the change, some individuals may experience measurable side effects. The good news is that the fall change is typically easier than the spring change, and simple light-timing and sleep basics can smooth the transition.
A brief history of Daylight Saving Time
The practice dates back to World War I. By adding an hour of evening light, the goal was more productive hours while also saving electricity and fuel. About 70 countries practice it, and it affects about a quarter of the world’s population. In many parts of the United States and Canada, changing the time twice a year is required, legally, despite ongoing debate about its utility. Critics have argued that the original energy-saving argument has not held up. Even the American Academy of Sleep Medicine recommends ridding the twice-yearly clock changes and keeping standard time.
The health impact of a one-hour time change
Our body runs on a tightly regulated 24-hour internal clock known as our circadian rhythm. The brain orchestrates this rhythm, and light is its most powerful timekeeper. When the clocks change, even by one hour, our circadian rhythm does not fall in line right away. For many of us, it can take several days to a couple of weeks to fully recalibrate, thus causing a temporary “circadian misalignment.” In a few cases, it can feel like mild jet lag from crossing one time zone. During this “circadian misalignment,” it’s not uncommon to have poor sleep quality the nights after the change, in addition to feelings of grogginess, fatigue, and diminished concentration. These symptoms are most pronounced when we lose one hour of sleep with the spring time change.
Is the fall time change harmful?
Thankfully, the fall time change is milder than the spring. For most of us, gaining an hour of sleep is much easier than losing one hour. Large studies have even suggested a small, short-term drop in heart problems and better mood afterward, likely from more morning daylight. But the “fall back” isn’t entirely harmless. Many are surprised to find they sleep a bit worse in the first week or two after the change, with difficulty falling or staying asleep being common, while others may experience a dip in mood as the evenings get dark earlier. I know I’m not alone in feeling a little down when I look outside at 4:30 pm, and it’s completely dark! Like you, there’s still so much of the day left to go. Thankfully, these effects are usually mild and resolve within a few days to weeks.
Your time-change toolkit
How can you prepare for the upcoming time change? The following simple steps will make it easier for your body and mind to adjust.
- Use light strategically
For the fall time change, get light in the late afternoon or early evening to help you stay awake. For example, a 30-minute walk after work or just before sunset may do the trick. Using light strategically during the day and early evenings will help delay your internal clock.
- Protect the basics of sleep
Stick to the sleep basics as much as possible. Keep a consistent bedtime and wake time as much as possible and minimize or avoid alcohol and caffeine around the transition since both disrupt sleep. Keep your bedroom dark, cool, and quiet; put away screens one hour before bed.
- Anticipate dips in mood
With the fall time change bringing earlier evenings quite suddenly, some may be prone to seasonal low mood, making it important to plan. Consider getting bright light every morning by going outside or use a 10,000-lux light box for about 30 minutes. If your low mood persists despite using light, reach out to your healthcare provider.
With good sleep habits and a few small adjustments to your light exposure, your body will settle into the fall time change so you can return to enjoying all the joys of the season.
