Leukocyte telomere length and mitochondrial DNA copy number association with colorectal cancer risk in an aging population

In this study, we evaluated the association of blood leukocyte telomere length (LTL) and mitochondrial DNA copy number (mtDNA-CN) with the risk of incident colorectal cancer (CRC). We studied and followed-up a cohort of Russian men and women (aged 45 – 69 years, n = 9360, 54% female) from the HAPIEE study for 15 years. Using the nested case-control design, we selected cases with incident CRC among those free from any baseline cancer (n = 146) and sex- and age-stratified controls among those free from baseline cancer and cardiovascular disease and alive at the end of the follow-up (n = 799). We employed multivariable-adjusted logistic regression to estimate the odds ratios (ORs) of CRC per 1 decile of LTL or mtDNA-CN. We observed an inverse association of LTL and mtDNA-CN baseline values with the 15-year risk of incident CRC. Carriers of shorter telomeres had an increased 15-year risk of incident CRC with adjusted OR 3.2 (95% CI: 2.56 – 3.87, P < 0.001) per 1 decile decrease in LTL, independent of baseline age, sex, smoking, body mass index, blood pressure, lipid levels, and education. Similarly, lower mtDNA-CN was associated with the higher risk of incident CRC with adjusted OR 1.7 (95% CI: 1.12 – 1.89, P < 0.001) per 1 decile decrease in mtDNA-CN, independent of the aforementioned factors. Using the modified values of LTL and mtDNA-CN adjusted for multiple factors and their interactions with a case–control status, the ORs of CRC were 2.53 and 1.52 per 1 decile decrease in adjusted baseline LTL and mtDNA-CN, respectively. In conclusion, LTL and mtDNA-CN were independent inverse predictors of the 15-year risk of CRC in the Russian cohort. These findings highlight the relevance for subsequent research to exploit the mechanisms through which LTL and mtDNA-CN may reflect human health.