Background Vitamin D deficiency has been associated with several chronic inflammatory diseases. However, only few studies have evaluated the vitamin D levels in spondyloarthritis (SpA) patients, with some controversial results.
Objectives a) To describe vitamin D status in a worldwide SpA population and b) to evaluate the association between vitamin D deficiency and demographic/geographic/season/SpA phenotype/disease activity and severity, and comorbidities.
Methods ASAS-COMOSPA is an international cross-sectional study, conducted in more than 15 countries representing the 4 continents. From a total of 3984 SpA patients included in the study, 1558 (39.1%) patients had available data on vitamin D level. Patients currently on vitamin D supplementation (528 patients) were excluded. The remaining 1030 SpA patients were included for this analysis.
Demographics, patients' phenotype, disease activity/severity measures (ASDAS-CRP, BASDAI, 44 swollen/tender joint index, physicians' global assessment, hip articular replacement, bamboo spine) and SpA patient's comorbidities (cardiovascular disease, osteoporosis, cancer, infections) were assessed. Vitamin D deficiency was defined as <20 ng/ml (50 nmol/L).
Statistical analysis: The mean ± SD of the available Vitamin D levels in the COMOSPA population and per country was calculated. Univariate and Multivariate analysis usinglogistic regression was performed to explain the variation in vitamin D deficiency in the COMOSPA cohort.
Results Mean vitamin D was 22.2 (±13.4) ng/ml, and vitamin D deficiency was observed in 527 (51.2%) patients.
In the univariate analysis, patients with vitamin D deficiency had higher body mass index (26.3±5.3 vs. 25.7±5.3, p=0.0251); were more frequently living in Europe (55.5% vs. 44.5%; p=0.0037), and in latitudes above 37° (53.0%vs 47.0%, p<0.008), were dosed for Vitamin D levels in winter-spring (56.8%vs 43.2%; p<0.0001), presented more frequently with radiographic sacroiliitis (80.5% vs66.2%; p≤0.0001), and positive HLA B-27 (81.8% vs. 76.2%; p=0.0422). Patients with vitamin D deficiency had also higher meanASDAS-CRP (3.0±1.3 vs. 2.7±1.2; p=0.0015), BASDAI (3.9±2.3 vs. 3.5±2.3; p=0.0142), and there were more patients withhip articular replacement (22 vs. 6; p=0.0033). After adjusting for age, gender and variables with p<0.1 in the univariate analysis, vitamin D deficiency remained significantly associated with season winter/spring (odds ratio (OR)1.88 [95%CI=1.24; 2.85], p=0.0029) and radiographic sacroiliitis (OR2.07 [95%CI=1.29; 3.31], p=0.0026). No independent association between vitamin D deficiency and comorbidities in this worldwide SpA population was found.
Conclusions As expected, vitamin D deficiency primarily occurs during less sunny seasons of the year. Moreover, this study suggests that: 1) vitamin D deficiency in SpA is frequent worldwide and 2) such vitamin D deficiency might be associated with both disease activity and (potentially more importantly) disease severity.
Acknowledgements Study was conducted under the umbrella of ASAS and financially supported by unrestricted grants from Abbvie, Pfizer and UCB.
Disclosure of Interest None declared