Comment: Cancer and high body-mass index

My commentary discussing the article, “Global burden of cancer attributable to high body-mass index in 2012: a population-based study” by Arnold and colleagues has just been published on The Lancet Oncology website:

Cairns BJ. Cancer and high body-mass index: global burden, global effort? Lancet Oncol 2014; Online First, 26 November 2014.

From the press release:

Writing in a linked Comment, Dr Benjamin Cairns from the University of Oxford in the UK says, “If 3·6% of all cancers are associated with high BMI, that is nearly half a million cancers, but this number is large mainly because the world population is large. Global health resources specifically for cancer prevention are not so large, and the resources targeted at obesity must be balanced against those for other important causes of cancer, particularly infections and tobacco use, which are each associated with much larger proportions of cases.”

I hope I’ll be able to post a paywall-free version of the full comment later. [UPDATE: This link might work.]  Until then, access is via the Lancet Oncology website:

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Framing the burden of cancer due to rising obesity

Here are two published statements about the additional burden of cancer which might be due to recent increases in the prevalence of obesity:

“Overall, a 1 kg m−2 increase in body mass index (BMI) is associated with an approximately 1% increase in incidence for all cancers combined (based on data from women) and about a 2% increase in total cancer mortality (based largely on data from men).”

and:

“We estimated that a 1 kg/m2 population increase in mean BMI would lead to 3790 additional patients in the UK each year developing one of the ten cancers that were overall positively associated with BMI.”

These two statements are entirely consistent.  The “3790 additional patients” is just over 1% of the roughly 330,000 people diagnosed with cancer each year in the UK.

The real difference between them is in how they are framed.  The first focuses on a small, dimensionless, relative increase, and the second on a seemingly large absolute number of unspecified but real, live patients.  Ultimately, the statements refer to the same finding, but they are supposed to mean different things to the reader.

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