Link Between Vitamin D Levels and Clinical and Serologic Factors Studied in SLE

The clinical and serologic association of plasma 25‑hydroxyvitamin D (25[OH]D) levels and the short-term effects of oral vitamin D supplementation in systemic lupus erythematosus (SLE) were assessed in a study published in Arthritis Research and Therapy.

The study was conducted in 2 phases among patients with SLE who met the Systemic Lupus International Collaborating Clinics (SLICC) 2012 classification criteria. Disease activity and damage were measured using the SLE Disease Activity Index-2000 (SLEDAI-2K) and the SLICC/American College of Rheumatology (ACR) Damage Index (SDI), respectively. 

In the cross-sectional phase 1 arm, the association between plasma vitamin D levels and clinical phenotype, disease activity, Galectin-9, and CXCL-10 was analyzed.

The interventional phase 2 arm was conducted to determine the effect of oral vitamin D supplementation on plasma vitamin D levels and disease flares. Patients with a SLEDAI-2K score of less than 10 who were receiving stable immunosuppressive therapy were randomly assigned to receive a high dose (ie, weekly dose of 60,000 units followed by a monthly dose of 60,000 units) or routine dose (ie, monthly dose of 30,000 units) of oral vitamin D for 6 months.

Vitamin D deficiency was defined as levels of 20 ng/mL or less and sufficiency was defined as levels of at least 30 ng/mL.

A total of 702 patients with SLE (93% women; mean age, 29.44±10.7 years; median disease duration, 16 months) were included in phase 1, with 41.5% having vitamin D deficiency.

Researchers noted a positive association of plasma vitamin D levels with age (P <.001) and a weak negative association with SLEDAI-2K (P <.001), but no significant association with disease duration, anti-dsDNA, CXCL-10 and, Galactin-9 (P >.05). After adjusting for all variables, enrollment center and age were found to be predictors of plasma vitamin D levels (P <.05).

A total of 172 patients (87 and 85 in the high- and routine-dose groups, respectively) were included in phase 2.

At 6 months, the researchers observed higher levels of vitamin D in the high- vs routine-dose group (9.5 vs 2.6 ng/mL; P =.04); vitamin sufficiency was also higher in the high- vs routine-dose group (63.6% vs 46.8%; P =.02, respectively). Incidence of flares was similar between the groups, with a total of 14 flares in the 6-month period. All adverse events were nonserious; no vitamin D toxicity was reported in both groups.

Study limitations included the lack of accounting for seasonal variations in vitamin D levels; the lack of data on vascular health and atherosclerotic disease; and the early termination of the trial due to the COVID-19 pandemic.

However, the study authors concluded, “High-dose oral vitamin D supplementation seems safe and more effective in improving vitamin D levels in SLE, but its role in modifying disease progress will need further studies.”