Attributable risk - background

The Fraction of Cancer Attributable to Lifestyle and Environmental Factors in the UK in 2010 (Parkin et al, 2011a).1:  Background - What is Attributable risk?

This page presents the background to a supplement published in the British Journal of Cancer on 6th December 2011. The analysis was undertaken at the Wolfson Institute of Preventive Medicine, Queen Mary University of London, with funding from Cancer Research UK. 

The study estimates the numbers and percentages (population attributable fractions, PAFs) of incident cancer cases predicted in the UK in 2010 that were linked to 14 lifestyle and environmental exposures. 1

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Lifestyle and environmental factors included

The exposures studied include both those that are linked to an increase in cancer risk and those that have been shown to have a protective effect, as below:


With the exception of radiation, the harmful exposures are theoretically avoidable, although may not be achievable in practice. For the beneficial factors, optimum exposure levels were chosen in line with health recommendations.

The PAFs should not be used to indicate the percentage of cancers that can currently be prevented by practical means without reference to the individual study sections in the BJC supplement, where some of the uncertainties and assumptions are discussed in detail.

section updated 07/12/11

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Comparison with previous studies

Parkin et al (2011p) provide a summary of how different factors are linked to cancer in the UK.16  Previous estimates published by Doll and Peto in 2003 are not directly comparable to the current study because they related to cancer deaths and did not give a breakdown by cancer site.17

The World Cancer Research Fund (WCRF) published estimates for the number of cancers attributable to diet, overweight and obesity and physical activity in 2002 in the UK and other countries.18 The estimates of the PAFs for these factors in the WCRF report are generally higher than in this study, with their estimate for the proportion of all cancers combined avoidable by changing exposure to diet, overweight and obesity and physical activity at 26%, compared with 18% in this study.16  The WCRF report did not examine the link with smoking.

The reasons for the higher estimates in the WCRF report than in Parkin et al (2011p)16 are noted, as follows:

  • Risk estimates were taken from individual studies, rather than using meta-analyses;
  • No lag period was used between assessment of exposure and year of cancer diagnosis;
  • More ambitious optimum exposure levels were set, based on the lowest risk groups within the studies selected for the risk estimates.

Cancers which have very different estimates between Parkin et al (2011p)16 and the WCRF report18 include liver (9% in Parkin et al (2011p)16 versus 17% in the WCRF report), pancreas (12% versus 41%), lung (9% versus 33%), breast (17% versus 42%), endometrium (36% versus 56%) and prostate (0% versus 20%). In contrast, estimates in Parkin et al (2011p)16 were slightly higher than the WCRF report for bowel and stomach.16,18

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References for attributable risk background

  1.  Parkin, DM, Boyd, L, Walker, LC (2011a) The fraction of cancer attributable to lifestyle and environmental factors in the UK in 2010. Introduction. Br J Cancer, 6 Dec 2011; 105 (S2):   S2-S5; doi: 10.1038/bjc.2011.474
  2.  Parkin, DM (2011b) Cancers attributable to consumption of alcohol in the UK in 2010. Br J Cancer 105 (S2):S14-S18; doi: 10.1038/bjc.2011.476
  3.  Parkin, DM (2011c) Cancers attributable to reproductive factors in the UK in 2010. Br J Cancer 105 (S2):S73-S76; doi: 10.1038/bjc.2011.488
  4.  Parkin, DM (2011f)  Cancers attributable to exposure to hormones in the UK in 2010. Br J Cancer 105 (S2):S42-S48; doi: 10.1038/bjc.2011.483
  5.  Parkin, DM, Boyd, L (2011d) Cancers attributable to dietary factors in the UK in 2010. III Low consumption of fibre. Br J Cancer 105 (S2):S27-S30; doi: 10.1038/bjc.2011.479
  6.  Parkin, DM, Boyd, L (2011e) Cancers attributable to dietary factors in the UK in 2010. I Low consumption of fruit and vegetables. Br J Cancer 105 (S2):S19-S23; doi: 10.1038/bjc.2011.477
  7.  Parkin, DM (2011g) Cancers attributable to infection in the UK in 2010. Br J Cancer 105 (S2):S49-S56; doi: 10.1038/bjc.2011.484
  8.  Parkin, DM (2011h) Cancers attributable to occupational exposures in the UK in 2010. Br J Cancer 105 (S2):S70-S72; doi: 10.1038/bjc.2011.487
  9.  Parkin, DM, Boyd, L (2011i) Cancers attributable to overweight and obesity in the UK in 2010. Br J Cancer 105(S2):S34-S37; doi: 10.1038/bjc.2011.481
  10.  Parkin, DM (2011j) Cancers attributable to inadequate physical exercise in the UK in 2010. Br J Cancer 105 (S2):S38-S41; doi: 10.1038/bjc.2011.482
  11.  Parkin, DM, Darby, SC (2011k) Cancers attributable to ionising radiation exposure in the UK in 2010. Br J Cancer105 (S2):S57-S65; doi: 10.1038/bjc.2011.485
  12.  Parkin, DM (2011l) Cancers attributable to dietary factors in the UK in 2010. II Meat consumption. Br J Cancer 105 (S2):S24-S26; doi: 10.1038/bjc.2011.478
  13.  Parkin, DM (2011m) Cancers attributable to dietary factors in the UK in 2010. IV Salt. Br J Cancer 105 (S2):S31-S33; doi: 10.1038/bjc.2011.480
  14.  Parkin, DM, Mesher, D, Sasieni, P (2011n) Cancers attributable to solar (ultraviolet) radiation exposure in the UK in 2010. Br J Cancer 105 (S2):S66-S69; doi: 10.1038/bjc.2011.486
  15.  Parkin, DM (2011o) Tobacco-attributable cancer burden in the UK in 2010. Br J Cancer 105 (S2):S6-S13; doi: 10.1038/bjc.2011.475
  16.  Parkin, DM, Boyd, L, Walker, LC (2011p) The fraction of cancer attributable to lifestyle and environmental factors in the UK in 2010. Summary and conclusions. Br J Cancer105 (S2):S77-S81; doi: 10.1038/bjc.2011.489
  17.   Doll R, Peto J (2003) Epidemiology of Cancer. In: Warrell D, Cox T, Firth J, Benz E, eds. Oxford Textbook of Medicine. 4th ed: OUP
  18.  World Cancer Research Fund/American Institute for Cancer Research (2009) Policy and Action for Cancer Prevention. Food, Nutrition, and Physical Activity: a Global Perspective. Washington, DC: AICR

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