Daylight Savings Time (DST) is back yet again. And not without consequences. The Monday following the time change hosts a 25% spike in the number of heart attacks, a 20% increase in road accidents and a 6% increase in workplace injuries. Why does that 60 minutes have such an impact on our health, performance and safety? The reason is that it messes with our body clock.
Our body has a clock, the circadian clock, which determines when we’re awake or sleepy during the 24 hour day. This clock synchronizes to time cues in the environment, the most important being the 24-hour light/dark cycle of the sun. Indeed, research at my former lab at the Ludwig-Maximilians University in Munich has shown that this synchronization is so sensitive, people wake up earlier as you go east within the same time zone!
DST pushes our social schedule an hour forward, but not the circadian clock, which remains attuned to the sun. This creates a circadian misalignment that is similar to jetlag. Even though we now have to rise an hour earlier, our circadian clock still wants us to sleep at the same time. Consequently most of us lose an hour of sleep for about a week after the spring transition.
While this affects anyone waking up to an alarm clock, there are steps to help you ease your circadian clock back on track.
- Go outside, especially in the morning. Outdoor light in the morning helps you adjust to an earlier wake-up time and bedtime. Take breakfast on your balcony, walk your kids to school, bike to work. Even on a cloudy day, the brightness from outdoor light (~ 1000 lux) far exceeds ordinary home lighting (~50 lux). If it’s still dark outside when you get to work, consider getting a light box.
- Don’t wear sunglasses. Light impacts the circadian clock via the eyes – not, as many assume, the skin.
- Dim your lights at night. While light is beneficial during the day, it has disruptive effects on your body at night. In particular, blue light interferes with circadian rhythms and melatonin secretion. Use dim yellow or red lights at night, starting three hours before sleep to help adjust to earlier sleep. Also limit exposure to screens three hours before sleep, including smartphones, tablets, laptops and close-range TV’s. Alternatively you can get free software that blocks blue light emitted from your screens at night: https://justgetflux.com/. Or wear blue blocking eyewear (blue blockers).
- Toss your melatonin (unless it’s a slow-release micro-dose). Commercially available melatonin (typically 1-10mg) far exceeds the amount your brain naturally produces (0.2mg) and its absorption extends into the next morning. This can shift your sleep cycle in the wrong direction, making you take longer to fall asleep at night.
- Make gradual changes. If you can, move your bedtime and wake-up time gradually over the course of a week or two by increments of 15 minutes a time. For those of you who use light therapy, start using the light gradually earlier in the morning, in steps of 15 minutes a time, starting 1-2 weeks ahead of the time change. You can also speed up the adjustment to DST by using the lights for 15 minutes longer than usual during the week before or after the transition to DST.