Association of serum 25-hydroxyvitamin D levels with fatigue severity in adults: A cross-sectional study

The objective of the study is to evaluate the association between serum 25-hydroxyvitamin D (25[OH]D) levels and fatigue severity.

This single-center, cross-sectional study included 228 participants aged 18-65 years who completed the fatigue severity scale (FSS) questionnaire. Individuals who had received vitamin supplementation within the previous 3 months, had known chronic disease, used regular medication, or had a history of antidepressant/anxiolytic use for depression/anxiety were excluded. Serum 25(OH)D, hemoglobin, ferritin, iron, magnesium, vitamin B12, and folate values were retrieved from the hospital information system. The Mann-Whitney U-test was used for comparisons between genders, and the Spearman correlation test was used for relationships between FSS and biochemical parameters. P<0.05 was considered statistically significant.

A total of 228 participants (57 males and 171 females) were included in the study. Most variables were not normally distributed; therefore, non-parametric analyses were performed. Spearman correlation analysis demonstrated a weak but significant negative correlation between FSS scores and both hemoglobin (p=0.003) and ferritin levels (p=0.001). No significant correlations were found between FSS and vitamin D, vitamin B12, folate, magnesium, or serum iron levels (p>0.05).In group comparisons based on fatigue severity, ferritin levels were significantly lower in the high-fatigue group compared to the low-fatigue group (p<0.001). Hemoglobin levels were also lower in the high-fatigue group (p=0.043). In contrast, vitamin B12 levels were significantly higher in the high-fatigue group (p=0.032). No significant differences were observed between groups in terms of vitamin D, folate, magnesium, or serum iron levels (p>0.05).

Serum 25(OH)D levels were not associated with fatigue severity. The observed relationship between fatigue severity and hematological markers (hemoglobin and ferritin) suggests that these parameters should be considered in the clinical evaluation of fatigue.