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Comment by csallen | Hacker News Reader

Is there a study that doesn't assume correlation == causation? Yes, lots of people who are generally unhealthy also have jobs that require sitting for hours at a time. But what does that mean for someone who lives an otherwise healthy lifestyle?

Let's say person A burns 1000 calories a day at his job, and only sits for a few hours when he goes home. Person B burns 1000 calories in his off time, but sits at work for 8 hours. Is person B still more likely to suffer health defects and die early? If so, why?

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All the studies so far indicate sitting (or other forms of inactivity) are bad no matter how much you exercise at other times.

The best natural experiment was the London bus driver study which showed huge differences in heart problems between drivers (sitting all day) and conductors (standing all day). Both were drawn from the same pool of employees and randomly assigned roles, so the experiment was naturally controlled for everything except the difference in behavior.

There were some other differences such as drivers having a more stressful job and conductors having more social interactions which might explain some of the differences in outcomes apart from the sitting/moving difference. But in any case, sitting for hours a day at a stressful job with minimal social interaction is incredibly bad for your health. Programmers take note!

Interesting. It would be a bit more legitimate of if the difference was between standing and sitting bus drivers (assuming there was some way to stand and drive a bus).

Or, straight to the point, if there was a study involving standing programmer and sitting programmers... preferably one in which the roles were randomized, because I'd suspect that programmers who've already chosen to stand while they work are probably a more health-conscious lot as it is.

Is this the study you refer to:

http://www.epi.umn.edu/cvdepi/study.asp?id=13

I can only thing of a few other differences besides sitting/standing people in this study that might make a difference. One is that I imagine the standing person absorbs the constant vibration of the bus better than the sitting person. Long term vibration is known to have deleterious effects.

I don't have access to the original paper but from the summary here http://www.epi.umn.edu/cvdepi/study.asp?id=13 it looks like the study was only observational, roles were not randomly assigned.

Person B is more likely to die early. Sitting is correlated with bad health, independent of your diet and amount of exercise.

http://www.ncbi.nlm.nih.gov/pubmed/22218159

Now, I'd love to see a randomized trial over a long time period to find out whether sitting actually causes bad health, or is just correlated.

I doubt we learned anything from the study above, bc your end conclusion is the exact question that the person before you led with.

It is relatively straightforward to control for things like "exercise from other activities" and underlying comorbidities in an attempt to compare "like with like" even for non-randomized studies.

One should also keep in mind that while correlation =/= causation, showing a strong correlation is a step along the path toward showing causation.

It is interesting is that an early study on the health impact of activity compared bus drivers and bus conductors, who also differ in sitting/standing:

http://circ.ahajournals.org/content/122/7/743.full#ref-1

Edit: sorry someone else had a better link:

http://www.epi.umn.edu/cvdepi/study.asp?id=13

I have to admit, this sounds a lot like that 8 glasses of water a day hocum that was floating around a few years back. Somebody finds some vague correlation in an abstract and blows it way out of proportion, leading to headlines that frankly don't make much sense.

I'd also like to see some real evidence.

You need about two quarts of water a day, but you can get this by consuming fruits and vegetables that range from 84% (apple) to 96% (iceberg lettuce) water by weight [see link below]. Drinking eight glasses of pure water a day is ridiculous unless you consume no food at all.

http://www.ca.uky.edu/enri/pubs/enri129.pdf

I don't think there's anything ridiculous about drinking 2 quarts of water per day. I easily drink 48-144oz of pure water per day with the 48oz bottle I carry with me everywhere I go (http://store.nalgene.com/Silo-p/2178-0048.htm)

Saying it's necessary to drink that much water might be ridiculous, and perhaps that's what you meant, but I don't think there's anything ridiculous about the activity itself.

>I don't think there's anything ridiculous about drinking 2 quarts of water per day.

What about diluting/pissing away vitamins and other essential compounds?

>I easily drink 48-144oz of pure water per day with the 48oz bottle I carry with me everywhere I go

Is this because you are constantly thirsty? If so you may want to be tested for diabetes.

http://www.mayoclinic.com/health/diabetes-symptoms/DA00125

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