Originally posted November 9, 2010

Have your internal clocks changed yet

November 9, 2010

I catch the bus to the train station each morning for work. I usually get to the train at right around 6:45am. When I arrive, there are a couple of things that are the same day-in and day-out. First, it’s dark. Like, I should still be sleeping dark. Like, why am I even out of bed right now dark. Like, it’s hard to imagine that my daughters woke me up an hour ago dark. Second, I can leisurely make my way up to the train. There is no rush. There is no crowding. There is no fight through the turnstiles. And, third, there is always someone passing out the free local newspapers. (This is great because I get my sudoku and crossword fix everyday on the train). Yesterday almost all of that changed. First it wasn’t pitch dark out. It didn’t look like the middle of the night as I trudged my way towards work. (Refreshing!) Second there were about twice as many people boarding my train as normal. (Not so refreshing.) Thankfully, we riders were still getting our free newspapers.

The obvious answer behind all of this is the change over from daylight savings time. But, were more people up and about because the sun was shining or because they forgot to change their clocks. Well, I will report (in my second super-scientific straw-poll of this post) that there were just as many people on my train this morning as there were yesterday.

So, what’s going on here. We all have our circadian clocks to thank for our ability to wake up so readily these days. Our bodies respond to different environmental stimuli to turn on and off different physiological functions. For example, we digest alcohol much better in the evening than we do during the day time (this is not a straw-poll, there is actual sciencebehind this claim). And, one of the main stimuli that we respond to (consciously and subconsciously) is light.

There are all sorts of studies trying to unravel the processes that go into the human response to light. One of my favorites looks at the science of the 5 o’clock shadow with respect to how hair follicles promote growth differently at different times of the day. (Seriously, these people need to win an Ig Nobel Award for this one; it’s just too good!) There are studieslooking at the role of melatonin production by the body in determining circadian rhythms. And, there is plenty of work being done to understand all of the feed-back control mechanisms that the body has built to effectively respond to circadian stimuli.

There has been relatively little work done to try and understand how toying with our natural circadian rhythms with daylight savings time physically and mentally affects us.

A map showing the countries that practice time changes for daylight savings time. DST was originally instituted to have more daylight hours in the afternoon than in the morning during the summer months. (Image credit)

A study published in 2007 and profiled here is one of the first pieces of research to really try to understand how the changes involved with DST affect our circadian clocks. The main result of this study found that people sleep an average of 20 minutes less per night during the summer hours when they are observing daylight savings time. That’s an hour every three nights, ten hours every month, over a day’s worth of sleep over the course of the summer. That’s a lot of sleep time we’re missing out on. The researchers, led by Till Roenneberg also found that people who like to stay up late and wake up early were more affected by DST than other people. The scientists determined that we were more affected by “springing forward” than by “falling back”.

Aside from this research, there was a study in the New England Journal of Medicine looking a the incidence of heart attacks surrounding changes to and from daylight savings time. The survey, performed by Imre Janszky and Rickard Ljung, found that your chances of having a heart attack in the spring when we change our clocks forward was increased over other times in the year. This increased occurrence of heart attacks lasted for several days after the actual time change. They also found that there was a smaller increase in occurrence of heart attacks when we change our clocks back from DST in the fall. However, this change only occurs on the first work day after the clocks fall back. Ergo, vis-a-vis, accordingly, DST might actually be bad for us …

So, I hope that you are enjoying the sunshine that we’re getting in the morning now that we are out of daylight savings time. It seems that our bodies have evolved to like it just this way.

Now, the only question remaining is to see how many days it takes before people are “over” the change from DST, and my trains aren’t as crowded on my trips into work.

-mrh