Daylight Savings – Modern Marvel Or Health Risk?

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Here comes the sun.

So, it’s been a week since daylight savings time ended with the “fall back into Fall” transition of one hour and everybody should be adjusted by now… or are they? (insert dramatic music here) Almost everybody complains about feeling fatigued and dragging themselves around the office the day after one of the time shifts, which is to be expected.

Your sleep schedule has been disrupted and it’s likely you didn’t sleep as much as you were used to. But how long does it actually take before we adapt to this unnatural time shift? A few days, a week, months?

I say unnatural because functioning according to the time shifts imposed by daylight savings forces the body to operate against it’s instinctual behavior of following seasonal daylight patterns.

Because of the tilt of the Earth, we have seasons, and those seasons coincide with a gradual increase and decrease of daylight throughout the year. Our bodies function along a 24 hour pattern scientifically referred to as our circadian rhythm. As the seasons change and the amount and timing of daylight during a 24 hour period changes, our bodies adapt to this through a process called entrainment.

It would seem that this process is beneficial to humans and other diurnal animals so that they will instinctively perform their necessary activities in daylight. We need the sunlight to help us to produce vitamin D, so making sure we are most active during the day would make sense. Conversely, at night when we are most vulnerable (because of fatigue and darkness) we will seek shelter and hunker down for the evening.

What are the consequences of subverting the natural human circadian rhythm through a process like daylight savings?

Paradoxically, daylight savings was intended to better match the activity peaks of a population with the available daylight hours. Of course, this is only necessary because of long entrenched social factors which govern the times of day in which people work. The strictly constrained periods of activity which are the domain of the modern working world bear no resemblance to a paleolithic hunter gatherer lifestyle, which would have been more fluid and random. So, it is not surprising that the process as a whole is very disruptive. How disruptive is it?

Studies of traffic accidents have indicated that the increased availability of daylight hours in the evening under daylight savings time may either reduce or increase the number of motor vehicle crashes and pedestrian fatalities, it’s rather inconclusive. Theoretically, if people drive less during times when it is dark, it would seem that accidents would decrease due to visibility reasons.

However, if people are now less rested or fatigued due to sleep disruption, the supposed benefits of daylight savings might be thwarted. In one study, a disruptive effect on circadian rhythms was seen for five days after the termination of daylight savings.

The transitional period may be even more disruptive to the circadian time-keeping system by driving the individual into a later activity phase (night owl). This may end with subsequent delays on top of the delayed phase position and thereby compromise well-being. Further, the ability to transition to daylight savings is “chronotype specific” meaning it is different between people who are more active earlier (larks) and those who are more active later (night owls).

The night owls, being active much later in the evening, and some getting less than the baseline of eight hours of sleep generally do less well at adjusting their sleep pattern to the change in timing.

This effect was even more pronounced during the Spring time period where an hour is lost rather than gained. So essentially, after being shifted to night owl status, they are hit again with a second penalty of being unable to adapt effectively. This compounding effect is what can cause adaptation to take up to a week or even much longer.

Finally, another way to look at daylight savings induced changes is that they are equivalent to traveling across timezones and experiencing jet lag. An example I found illustrated that the one hour advance in Spring corresponds to traveling from Central Germany to Morocco and back in Autumn, without changing time zone or climate. Messing with people’s sleep like this is no trivial matter.

Proper amounts of restful sleep is important for a host of key metabolic factors including cortisol regulation, tissue growth and repair, and even body composition. At the worst, sleep disruption has the potential to increase insulin resistance and over long periods the probability of developing diabetes. Thankfully, it will be a while till we have to deal with this mess again.

Do any of you have trouble dealing with the time changes due to daylight savings? What kinds of things do you do to help shift your sleep cycle and get back to normal?

Referenced in this article:

1. Kantermann T, Juda M, Merrow M, Roenneberg T. The human circadian clock’s seasonal adjustment is disrupted by daylight saving time. Current biology : CB. 2007;17(22):1996-2000. Available at: http://www.ncbi.nlm.nih.gov/pubmed/17964164.

2. Lahti T a, Leppämäki S, Ojanen S-M, et al. Transition into daylight saving time influences the fragmentation of the rest-activity cycle. Journal of circadian rhythms. 2006;4:1. Available at: http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1382261&tool=pmcentrez&rendertype=abstract.