Pernicious use of surrogate markers

I am delighted that the BMJ recognises the importance of bicycles to international health.1 However, the article is seriously flawed. First reports in a new field tend to be the most cited, regardless of subsequent and contrary evidence from better designed studies. Why has the BMJ allowed open access to this work? Now, rather than being confined to a small number of experts with the knowledge, skills, and training to evaluate the weaknesses of the claims made, the article is accessible to a general public that seriously lacks these attributes. Among those to whom the conclusions are available are spouses, partners, and family members of cyclists. Most of these people are greatly influenced by pseudo-scientific claims appearing in print and electronic media and reluctant to acknowledge alternative viewpoints, no matter how well reasoned and scientifically sound.

It is ironic that Groves compares the uptake of new cycling technology to the uptake of new drugs when his major error is identical to one often encountered in drug trials—the measurement of surrogate outcomes. Who cares whether you save four minutes riding from Sheffield to Chesterfield? The more important questions are how does the rider feel about the journey on one type of bicycle versus the other; what impact does the bicycle have on the rider’s self esteem and feeling of worth; how are the rider’s interactions with colleagues, friends, and family affected by the type of machine that he or she rides? Until researchers shift their focus from the mechanistic to the psychosocial aspects of cycling, many of us will be condemned to riding junk.