Although previous studies suggested that depressed mood and fatigue among cancer survivors are associated with chronic inflammation, the effect of cytokines on the relation between physical activity and fatigue and depressed mood is characterized by inconsistent results. The aim was to examine levels of pro-inflammatory (IL-6, IL-8, TNFα, IL-12) and anti-inflammatory (IL-10) cytokines in relation to the effects of physical activity on fatigue and depressed mood.
Breast cancer survivors (n = 108; stages I-III), aged >20 and who were 1-6 months postchemotherapy were recruited consecutively. Participants completed the Fatigue Symptom Inventory and Center for Epidemiologic Studies Depression Scale and reported physical activity details; 10 cc of blood were drawn for assessment of levels of IL-6, IL-8, IL-10, Il-12, and TNFα in serum.
Only IL-6 and IL-8 were associated with fatigue and depressed mood. Controlling for background variables, physical activity and IL-6 were significantly associated with fatigue, but only physical activity was significantly associated with depressed mood. A moderated effect of IL-6 and IL-8 was found in the association of physical activity and fatigue, indicating that this association is significant only in individuals with lower levels of IL-6 or IL-8.
Fatigue and depressed mood are differently associated with pro-inflammatory cytokines. In addition, IL-6 and IL-8 are main cytokines affected by physical activity. The study stresses the need to provide information and tailored guidance for cancer survivors for maintaining an active lifestyle into survivorship and the importance of allocating resources for programs to encourage active lifestyles among cancer survivors. Caution should be exercised in the interpretation of the results due to the cross-sectional design and possibility of bidirectional associations between the study variables.

Copyright © 2018. Published by Elsevier B.V.
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