Background: Early detection of vitamin D deficiency in patients with Systemic Lupus Erythematosus (SLE) may prevent or reduce fatigue, sleep and quality of daily life impairment.
Objectives: to assess vitamin D deficiency or insufficiency in SLE patients, and to correlate it with clinical disease activity, sleep and quality of life impairment.
Methods: 80 SLE patients plus 40 healthy volunteers as a control group. Sleep quality assessed by Pittsburgh Sleep Quality Index; disease activity assessed by SLE Disease Activity Index 2000. Functional capacity assessed by health assessment questionnaire. Serum Vit D measured by ELISA.
Results: Serum vitamin D (25-OH D) levels were significantly lower in SLE patients compared to controls (p = 0.02).  The lowest vitamin D level was detected in SLE patients with lupus nephritis (p = 0.003).
There was a significant difference in SLEDAI, PSQI, FACIT-F, HAQ and SLE-QoL scores between SLE patients with sufficient and insufficient/deficient vitamin D serum levels (p= 0.028, and 0.001).
a significant negative correlation between serum vitamin D level with clinical disease activity, functional capacity, sleep and quality of life.
Conclusion: Vitamin D may play an important role in the pathogenesis of SLE and could be a promising biomarker of SLE disease activity.