Is TV changing our circadian rhythms?

i-75fa6f7cebb4145668724f37f5a52b36-steve_icon_medium.jpgSo I hate daylight savings time. It doesn't save energy, I doubt it helps farmers like it supposedly did, and I always forget to set my clocks back. How many of you have a clock that is only correct half of the year because you don't want to set it?

Now I have something else to get pissed off at for messing with my sleep. According to a study entitled "Cues for Timing and Coordination: Latitude, Letterman, and Longitude," by Daniel S. Hamermesh, Caitlin Knowles Myers, and Mark L. Pocock published in the Journal of Labor Economics, television is impacting our circadian rhythms, especially depending on where we live and what we do for a living.

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Here's the basics of the study:

For their study, the authors turned to data provided by the unprecedented Bureau of Labor Statistics' American Time Use Survey (ATUS), which enabled them to observe how Americans split their time between their three most time-consuming activities: work, sleep, and television watching. After merging ATUS with sunrise and sunset data, the authors found that while natural daylight patterns have some effect on people's life patterns, the demands of global business -- market openings, etc -- and regular television schedule demarcate the boundaries of most Americans' lives. Says Hamermesh, he and his colleagues were "amazed how little daylight matters nowadays, and how much artificial time zones matter."

and some more data:

* If you are in the "professional service" sector (finance, information, business services), you are more likely to follow the time zone cue, while you are in other services sector (education, health, leisure, and hospitality), you are probably more responsive to television cues.
* The probability that you are watching TV between 11-11:15 p.m. decreases with age, but the probability that you are at work between 8 and 8:15 a.m. increases until retirement age.
* Marital status and children don't have an effect on TV viewing at 11 p.m., but married individuals are less likely to be sleeping at 7 a.m. and more likely to be at work at 8 a.m.
* Individuals in early television zones (Central and Mountain) are 6.4 percentage points less likely to be watching television between 11 and 11:15 p.m. than those in later zones, but if the sunset is pushed back by an hour the probability of watching TV at 11pm only increases by about one percentage point.

I would be very interested in seeing how the culture of TiVo will affect data like this. I very rarely stay up to watch a television program anymore since I know it will be ready for me to watch sans commercials the next day when I'm not so exhausted. Then again I don't think a nuclear explosion could keep me from my bed at night.


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The clock over the front door of my house is always set to Central Standard Time. ;P

By Matt Platte (not verified) on 07 Mar 2008 #permalink

Well, since I have a PVR and I am self-employed and work at home, I get up when it gets light out, and I go to bed when I get tired. Highly recommended. I don't care what time it is, but I also hate daylight savings time because I prefer to wake up earlier and I really can't force myself to do that any more when it's dark.

Is TV full-spectrum light? What I mean is, I wonder if TV can actually entrain the internal clock via melanopsin essentially dictating via hormones the sleep-wake cycles of night TV-watchers.

Thank you! I think TV is full spectrum. It certainly contains the blue portion, which is what melanopsin is most sensitive to. I am just not sure if the intensity of light is high enough - the literature on humans is controversial as to the intensity needed for a phase-shift.

Well, I don't forget and I don't mind when the time changes. It's not that hard to change the couple of clocks, and the watch.

Also, I DVR. Since I get up at 5 am, I never watch TV at 11. Or 10, for that matter.

I don't have Tivo, but I do have a VCR. I record prime time programs and then replay them the next day when it's convenient for me to watch. And my bedtime is now 8 pm, because my neighbors get very quiet then, thanks to prime time, making it easy for me to fall asleep.

One year I worked an outside job from dark until dark, seven days a week. Within a couple months, I didn't need to use my watch. I could tell the time from the Sun position, and my brain automatically adjusted for the northing and southing of the Sun. I did not observe DST since I wasn't working on clock time.

By the way, dairymen do not switch their cows to DST. Time shifts are very disturbing to milk cows. All the other animals on the farm expect to be fed on time as well.

Yeah, I'd be interested to see how this relates to DVRs. The only TV I watch is recorded with my DVR or accessible anytime On Demand.

By Ben Wraith (not verified) on 07 Mar 2008 #permalink

What about computer screens? Would surfing the internet late at night have the same effect?

I don't own a tv and can count my tv viewing easily in "hours per decade" (really) and the time changes generally mess me up, particularly switching back to standard time. On the other hand, I'm what chronobiologists call "an extreme owl," so I figure that has something to do with it.

By Interrobang (not verified) on 08 Mar 2008 #permalink

I'm just happy to have that extra hour of daylight when I get out of work! I pretty much go straight to work when I get up, and I hate it when I leave and it is either already dark or gets dark shortly after. Basically, my leisure time always comes in the evening, and I appreciate having some daylight then! I am fairly certain that the TV has little effect on MY sleeping patterns...