Geographical differences in lifestyle factors and occurrence of colorectal cancer in Norwegian women

What is it about?

Norway has experienced an unexplained and steep increase in bowel or colorectal cancer (CRC) occurrence in the last 50 years. Lifestyle factors have substantial influence on the occurrence of CRC. This study aimed to determine whether geographical distribution of lifestyle factors could explain these geographical differences in CRC occurrence in Norwegian women. We used self-reported information from 96,898 women regarding their lifestyle factors in the Norwegian Women and Cancer Study. We estimated the relative risks associated with the lifestyle factors. We further investigated the extent to which these factors accounted for the observed differences in geographical areas of low and high CRC occurrence. We found that height, being a former smoker who smoked ≥10 years, or being a current smoker who has smoked for ≥10 years relative to never smokers, was associated with increased CRC risk. Duration of education >12 years (vs ≤12 years), and intake of vegetables and fruits >300 g (vs ≤300 g per day) were associated with reduced CRC risk. Factors such as physical activity, body mass index, alcohol intake, red or processed meat intake, were not associated significantly. All the factors explored, together did not account for the differences in CRC risk between geographical areas of low and high CRC occurrence. In conclusion, lifestyle-related CRC risk factors did not explain the geographical differences in CRC occurrence among Norwegian women. Possible explanations may lie in heritable factors.

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Why is it important?

Family history of CRC may be important in deciding the appropriate preventive screening strategy in areas of high CRC occurrence.