Objective Epidemiological associations suggest vitamin D may play a role in inflammation and atherosclerosis. Using frozen serum and data from the Atherosclerosis Prevention in Pediatric Lupus Erythematosus (APPLE) trial, we assessed associations between 25-hydroxyvitamin D [25(OH)D] and measures of systemic lupus erythematosus (SLE) disease activity and cardiovascular risk.

Methods Baseline APPLE serum samples were used to measure 25(OH)D levels. Logistic regression models for vitamin D deficiency [25(OH)D levels <20 ng/mL] were constructed using baseline variables collected as part of the trial, including race, season, latitude, disease duration, disease activity, high-sensitivity C-reactive protein (hsCRP), proteinuria, fasting lipids and carotid intima medial thickness (CIMT).

Results Samples were available from 201 of 221 APPLE subjects; 61/201 (30%) had vitamin D deficiency at baseline. In univariable analysis, baseline vitamin D deficiency was associated with season (p<0.01), minority status (p<0.01), body mass index (p=0.04), duration of SLE (p<0.01), SLICC damage index (p=0.04), hsCRP (p<0.01), mean–max CIMT (p=0.01), LDL-cholesterol (p=0.03) and timed urine protein (p=0.03). In multivariable modelling, vitamin D deficiency was associated with age, latitude, season, minority status, proteinuria and hsCRP.

Conclusions Vitamin D deficiency is common in paediatric lupus and is independently associated with elevated hsCRP, a marker of inflammation that predicts cardiovascular disease risk. Although association is not proof of causation, this association is novel in the paediatric SLE population and suggests that vitamin D deficiency may contribute to heightened inflammation and cardiovascular risk in this population.

Trial register number NCT00065806.