Inflammation Is a Mediating Factor in the Association between Lifestyle and Fatigue in Colorectal Cancer Patients

Fatigue is very common among colorectal cancer (CRC) patients. We examined the association between adherence to the World Cancer Research Fund/American Institute for Cancer Research (WCRF/AICR) lifestyle recommendations and fatigue among stage I-III CRC patients, and whether inflammation mediated this association. Data from two prospective cohort studies were used. Adherence to the WCRF/AICR recommendations was expressed as a score ranging from 0-7, and assessed shortly after diagnosis. Six months post-diagnosis, fatigue was assessed with the European Organization for Research and Treatment of Cancer quality of life questionnaire C30 (EORTC QLQ-C30), and in a subpopulation, the plasma levels of inflammation markers (IL6, IL8, TNFα, and hsCRP) were assessed. Multiple linear regression analyses were performed to investigate the association between adherence to the WCRF/AICR recommendations and fatigue. To test mediation by inflammation, the PROCESS analytic tool developed by Hayes was used. A higher WCRF/AICR adherence score was associated with less fatigue six months after diagnosis (n = 1417, β -2.22, 95%CI -3.65; -0.78). In the population of analysis for the mediation analyses (n = 551), the total association between lifestyle and fatigue was (β -2.17, 95% CI -4.60; 0.25). A statistically significant indirect association via inflammation was observed (β -0.97, 95% CI -1.92; -0.21), explaining 45% of the total association between lifestyle and fatigue (-0.97/-2.17 × 100). Thus, inflammation is probably one of the underlying mechanisms linking lifestyle to fatigue.