Effect of Vitamin D Deficiency on Fatigue in Systemic Sclerosis: A Cross-sectional Study

Objective: The purpose of this study was to explore the relationship between vitamin D deficiency (VDD) and fatigue severity, as well as its relationship with sleep quality, in subjects with systemic sclerosis (SSc). Method: Our cross-sectional research included 98 subjects who were diagnosed with SSc according to EULAR/ACR 2013 classification criteria. Demographic, clinical, and laboratory data, including vitamin D (VitD) levels, were collected. Sleep quality was investigated with the Pittsburgh sleep quality index (PSQI) and fatigue severity with the multidimensional assessment of fatigue (MAF) scale. Results: Subjects with VDD exhibited significantly poorer sleep quality as indicated by PSQI scores (12 vs. 8; p<0.001) and higher MAF scores (34.5 vs. 22.4; p<0.001). Multivariate analysis identified MAF score [odds ratio (OR): 1.204, 95% confidence interval (CI): 1.116-1.298, p<0.001] and disease symptom duration (OR: 1.009, 95% CI: 1.002-1.016, p=0.001) as independent predictors of VDD. ROC analysis demonstrated that an MAF score ≤27.7 and PSQI score ≤10.5 were optimal cut-off values for predicting VDD. Significant negative correlations were observed between VitD levels and MAF (r=-0.610, p<0.01) and PSQI (r=-0.346, p<0.01). Conclusion: VDD is significantly associated with increased fatigue and poorer sleep quality in subjects with SSc. These signs indicate that addressing VDD through routine screening and supplementation may alleviate fatigue, enhance sleep quality, and raise the quality of life in SSc subjects.