Error in figures 2, 3 and 4
We were reading this article only recently and noticed that there is
a printing error in the labels for the x-axis in figures 2,3 and 4. The
centre point should not be "zero", but should be labelled as "one". In
addition, the numbers to the left of the centre point should not have
When presenting relative risks in a figure it is not possible to plot
zero anywhere on the axis, nor can a relative risk have a negative value.
Since it is an on-line version that readers are accessing, I assume
that changes to the document are still possible and you might want to
consider correcting the problem.
Competing interests: No competing interests