The Dangers of Daylight Savings Time
Daylight savings time (DST) heralds longer days, more sun, and warmer temperatures, but did you know that it is also associated with an increased risk of fatal car accidents? Multiple research studies have found a higher rate of car accidents on the Monday following the shift to DST. The same association is not found with the Autumn time shift. But what's behind the statistics? To fully grasp the problem and how we can manage it, we need an understanding of our internal body clocks.
Our bodies are naturally programmed to have daily cycles, called circadian rhythms, that govern many mental and physiological domains. For the sake of this discussion, let's say that you typically have the common sleep schedule of an 11 p.m. - 12 midnight bedtime and a 6-8 a.m. rise time. The graphic below represents how your alertness would fluctuate throughout the day on such a schedule:
As you can see, there are separate alertness peaks mid-morning and in the late evening. Most people who keep the above sleep schedule will be maximally alert somewhere around 9 p.m.
It makes sense that our circadian rhythms are not fixed; otherwise, we'd never be able to adapt to new locations in different time zones. But circadian rhythms change relatively slowly and, for unclear reasons, it's easier to "phase delay" our rhythms (be able to stay up later) than "phase advance" (be able to go to bed earlier); in general, it takes us 50% longer to adjust to phase advances than delays. The rule of thumb is that it we can phase advance approximately one hour per day.
During DST, we are asking our bodies to phase advance. Instead of going to bed at 11 p.m. when our bodies are naturally sleepy, we try to go to bed at the new 11 p.m. clock time but our bodies still think it's 10 p.m.! At 10 p.m., we are still coming off our maximal alertness peak and falling asleep is likely to be difficult. Couple this problem with the possibility that we just lost an hour of sleep with the time change due to having to get up for our usual Sunday responsibilities, and it can be a dangerous combination leading to significant sleep deprivation on Monday morning.
What You Can Do
To ensure a smooth transition through DST, the following countermeasures may be helpful:
- Try to pre-adapt before DST: Try going to bed 20 minutes earlier than usual for the three nights leading up to DST. Getting exposure to bright light first thing in the morning immediately after awakening for 15-20 minutes will help promote the phase advance of your circadian rhythms.
- Strategic use of melatonin: Melatonin exerts a powerful influence on our circadian rhythms. Taking some melatonin four to five hours before your desired bedtime can help you fall asleep at that time. So for instance, if your normal bedtime is 11 p.m., take melatonin at 6 or 7 p.m. on the Sunday of DST. Research shows that a small dose of melatonin, like 0.5 mg or less, may be as effective as larger doses (3 mg is the most common dose) and is less likely to result in drowsiness.
- Strategic use of caffeine: If you're dragging on Monday, March 13th, taking some caffeine can help combat mental fatigue. Just remember that it takes 20-30 minutes for your body to absorb the caffeine from your GI tract.
- Move to Arizona! The Grand Canyon State is the only state in the Continental United States that does recognize daylight savings time.