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Association between active commuting and incident cardiovascular disease, cancer, and mortality: prospective cohort study

BMJ 2017; 357 doi: https://doi.org/10.1136/bmj.j1456 (Published 19 April 2017) Cite this as: BMJ 2017;357:j1456

Re: Association between active commuting and incident cardiovascular disease, cancer, and mortality: prospective cohort study

It worries me that, although the paper has the usual token nod to the problem of causality, it's written entirely as though it demonstrates tha biking to work has all sorts of benefits. The related editorial is even more more cavalier : the title "Active commuting is beneficial for health" is a direct statement of causality.

In particular, the paper doesn't discuss at all the possibility of reverse causality. It would not be at all surprising if people with heart disease or cancer were incapable of walking or biking to work. or at least disinclined to do so.

It's also very likely that people who bike to work are also health conscious in all sorts of other ways.

Of course I'm 100 percent in favour of people walking or biking to work. It would make the streets a lot more pleasant for everyone. But it isn't good when evangelism replaces science. Causality really matters.

Incidentally, why are the reviews of this paper? Why are they not avaliable?

Competing interests: No competing interests

20 April 2017
David Colquhoun
Research professor
UCL
London
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