Vitamin D and Fatigue in Palliative Cancer: A Cross-Sectional Study of Sex Difference in Baseline Data from the...

Fatigue is one of the most distressing symptoms in patients with advanced cancer. Previous studies have shown an association between low vitamin D levels and fatigue. The aim of this study was to investigate the association between vitamin D levels and self-assessed fatigue in cancer patients admitted to palliative care, with focus on possible sex differences. This is a cross-sectional study. Baseline data from 530 screened patients, 265 women and 265 men, from the randomized placebo-controlled trial "Palliative-D" were analyzed. Vitamin D status was measured as 25-hydroxyvitamin D (25-OHD) and fatigue was assessed with EORTC-QLQ-PAL15 and with Edmonton Symptom Assessment System (ESAS). In men, there was a significant correlation between 25-OHD and fatigue measured with the "Tiredness question" (Q11) in EORTC-QLQ-PAL15 (p < 0.05), where higher 25-OHD levels were associated with less fatigue. No correlation between 25-OHD and fatigue was seen for women. Fatigue measured with ESAS did not show any significant association with 25-OHD levels neither in men nor in women. Low vitamin D levels were associated with more fatigue in men but not in women. The study underscores the importance of subgroup analysis of men and women when evaluating the effect of vitamin D in clinical trials since the effect may differ between the sexes. The ongoing "Palliative-D study" will reveal whether vitamin D supplementation may counteract fatigue in both men and women. ClinicalTrial.gov: NCT03038516.