I haven’t liked this whole switching back and forth between Daylight Saving and Standard time since high school. Back then, I worked in a 24-hour restaurant and every Saturday, I worked from 6pm to 3am. This was not a particularly fun shift and by the end I was usually dead tired (and sick to death of the drunk people who came in after the bars closed at 2am). Every fall, it was made even more not fun by the switch from Daylight Saving to Standard time when at 2am, the clock got turned back. Apparently this event got loud cheers at the bar, but for me it meant that I had to stay an extra hour (and deal with extra drunk people).
I never seemed to get any benefit from that “extra” hour, even after I left that waitressing job. Most years, I would forget to change the clock and show up an hour early to church on Sunday.* So, I never really got that “extra” hour of sleep that everyone says is the big advantage to changing the clocks.
In most recent years, the time change has been especially grueling because I have developed Seasonal Affective Disorder. I am now exquisitely sensitive to when the sun rises and sets and when I get out of bed and eat meals and go to bed in relation to that cycle. So twice every year, my system gets thrown into a state of shock—a prolonged jet-lag—when the time changes. I am not exaggerating when I tell you that the time changes throw me off-balance for weeks. I’m not hungry at the right times, I don’t wake up at the right times, I feel tired all the time. Really, really tired.
I can hear you all now, you’re saying, “But it’s just one hour! How can it affect you so profoundly?” You may also be thinking that the time change doesn’t affect you. You would be wrong. In blog-surfing over at Scienceblogs, I came across a post at A Blog Around the Clock mentioning this (pdf)** study by Kantermann, Juda, Merrow, and Roenneberg.
From the abstract: “Our data indicate that the human circadian system does not adjust to DST and that its seasonal adaptation to the changing photoperiods is disrupted by the introduction of summer time.” Good luck trying to convince my coworkers of that.
Chronobiology is not my specialty, but I was able to glean a few things from the paper. One was that sleep timing changes according to the time of dawn during standard time, but is static during daylight saving time. One caveat of this is that as far as I can tell, they did not do the same study with a population of people who do not switch between standard time and daylight saving. The authors address this point mentioning that it seems unlikely that there is a threshold dawn time after which everyone’s sleep times would so abruptly stop changing. Another interesting point was that how much you are affected by the time change depends on your “chronotype.” I don’t fully understand the terminology, but I think in this case chronotype refers, in layperson’s terms, to whether or not you are a “morning person.” It seems that morning people more readily adjust to the time change in the spring.
Practically speaking, what does this mean? Well, this being a scientific study, the conclusions the authors come to are limited by the scope of the study and the data gathered from it. The authors are careful to not state whether this affect is “good” or “bad.” They do point out that the time change disrupts our seasonal timing, and that humans are seasonal animals although humans residing in industrialized countries have become less and less seasonal. It could be that the time change contributes to our loss of seasonality.
Given the data in this study, I think we can reasonably assume that the time change has more of an affect on people than they realize. The study shows that the time change affects activity levels, sleep and wake times, and sleep duration. Many people think that they are not affected by getting slightly less or more sleep than usual but this is false. The amount of sleep we get can have a profound impact on our cognitive abilities.
I feel somewhat vindicated by this study. Now, when people are incredulous about my inability to adjust to the time change, I can point them to this study. It can be a real comfort to have science on your side.
*Actually, the time change in spring was worse as far as church was concerned because sometimes it fell on Palm Sunday when the services were extra long and people would show up an hour late and end up coming into the middle of Mass and wondering what was going on.
**This paper seems to be an e-pub and has appeared before the print copy of the journal has come out. The current citation for the paper is:
Kantermann et al., The Human Circadian Clock’s Seasonal Adjustment Is Disrupted by Daylight Saving Time, Current Biology (2007), doi:10.1016/j.cub.2007.10.025
The hard-copy print version will appear in the November 20 issue of Current Biology (volume 17).