Aleksandrova K, et al. - This study assessed the contribution of body fatness and biomarkers of various biologically plausible pathways to the link between physical activity and colon cancer. Findings suggested that a strategy comprising physical activity promotion, particularly outdoors, and maintenance of metabolic health and adequate vitamin D levels could be promising for colon cancer prevention.

Methods

• Researchers performed a nested case-control study in a cohort of 519 978 men and women aged 25 to 70 years followed from 1992 to 2003.
• They used risk-set sampling to match a total of 713 incident colon cancer cases to 713 controls on age, sex, study centre, fasting status and hormonal therapy use.
• The amount of total physical activity during the past year was expressed in metabolic equivalent of task [MET]-h/week.
• In addition, anthropometric measurements and blood samples were collected at study baseline.

Results

• Findings demonstrated that high physical activity was associated with a lower risk of colon cancer: relative risk ≥91 MET-h/week vs <91 MET-h/week = 0.75 [95% confidence interval (CI): 0.57 to 0.96].
• Data also reported that in mediation analyses, this link was accounted for by waist circumference: proportion explained effect (PEE) = 17%; CI: 4% to 52%; and the biomarkers soluble leptin receptor (sOB-R): PEE = 15%; 95% CI: 1% to 50% and 5-hydroxyvitamin D (25[OH]D): PEE = 30%; 95% CI: 12% to 88%.
• Researchers noted that in combination, these factors explained 45% (95% CI: 20% to 125%) of the association.
• They also noted that beyond waist circumference, sOB-R and 25[OH]D additionally explained 10% (95% CI: 1%; 56%) and 23% (95% CI: 6%; 111%) of the association, respectively.