You better sit down for this

Most journal papers go unnoticed by general public until a version of it sans any of the caveats mentioned in the study pop up in popular media. There is one such article from Quartz that gives us a dire warning about our sedentary work life. You better sit down for this, errr  stand up,

Why not even exercise will undo the harm of sitting all day

Quoting from a recently published meta-analysis of observational studies the article says, (emphasis mine)

Sitting can be fatal.

It’s been linked to cancerdiabetes, and cardiovascular disease. In this latest meta-analysis, Daniela Schmid and Michael F. Leitzmann of the University of Regensburg in Germany analyzed 43 observational studies, amounting to more than 4 million people’s answers to questions about their sitting behavior and cancer incidences. The researchers examined close to 70,000 cancer cases and found that sitting is associated with a 24% increased risk of colon cancer, a 32% increased risk of endometrial cancer, and a 21% increased risk of lung cancer.

Before we look at the numbers let me tell you I spend most of my workday standing up. I am fortunately enough to have a standing desk and even when I did not have one I rigged up one by placing the monitor on a book shelf and propping up boxes on the work desk. I should be happy to jump on this evidence and tout it as validation of my behavior. A part of me did that. But however favorable a piece of evidence looks like you need to question the method it was arrived at.

While the reported study was enough for some to make a case for standing up some of us have a the undesirable job of calling into question the hypothesis formation, data and method.

Here are the problems I see in adopting this report

  1. All the studies included in the meta analysis are observational studies and not controlled experiments – which is very hard if not impossible to do with sitting/standing.
  2. The studies are based on self-reporting by participants and not based on observations by experimenters – so it is hard to verify whether or not the subjects exercised as they reported.
  3. The meta-analysis clearly states this is just correlation – that is lost on Quartz. When you see a statement like, “sitting is associated with a 24% increased risk of colon cancer”, you must ask, “is it likely that the people are sitting down because of the illness?”
  4. Finally what does the 24% increased risk mean? It is the relative risk that is increased. If people who sit 0 hours are at x% risk of getting colon cancer those who sit 8 hours are at risk of 1.24x%.   Colon cancer is indeed the second leading cause of cancer related deaths in US but you should note that its incidence rate is 1 in 20 or 5%. And individual factors affect the incidence rate far more than other factors.

So at 1.24 times relative risk if you are sitting down for 8 hours of work the incidence rate goes from 5% to  6.2%. But what other factors have higher relative risk that you should worry about?

If you want a standing desk, get it. But don’t settle for correlational studies to make a case for it.

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