Cancers attributed to modifiable factors in Norway 2016-2020

Background: Targeting modifiable factors offers significant potential for primary cancer prevention. For public health strategies, it is essential to quantify the contribution from each factor on a national level. We estimated the contribution of 12 modifiable factors on cancer incidence in the Norwegian population.

Methods: Nationally representative data (1990-2015) on the prevalence of tobacco smoking, over-exposure to ultraviolet radiation (UVR), alcohol consumption, physical inactivity, overweight and obesity, intake of processed and red meat, fibre and calcium, menopausal hormone therapy (MHT), human papilloma virus (HPV) infection and insufficient breastfeeding were collected from health surveys. Using these prevalences, cancer risk estimates for for the exposures, and average annual cancer incidence rates for 2016-2020, we estimated annual population-attributable fractions (PAFs) and numbers of preventable cases.

Results: Of the average 24,608 annual cases of cancers related to our included modifiable factors, 12,12,250 (6240 in women and 6009 in men) (41 %) were attributed to these factors. Tobacco smoking caused the highest proportion of cancers cases, 20 % in men and 13 % in women. Sunburn and indoor tanning caused 13 % and 10 % of cancers in men and women, respectively, and overweight and obesity caused 4.5 % of the cases. Cancers of skin, lung, colon and female breast had the highest number of preventable cases.

Conclusion: Over a third of the annual cancer cases in Norway were attributed to 12 modifiable factors. Based on this study, efforts to reduce tobacco smoking, UVR over-exposure, and overweight and obesity could be the most effective in primary prevention of cancer.