The association of metal exposure and Sjögren's disease: a comparative study

Background Sjögren's disease (SjD) affects the ocular surface and oral health and has systemic manifestations. We investigated metals as potential triggers and diagnostic markers in the pathophysiology of SjD. Methods The comparison made between SjD (n = 57), in accordance with the guidelines of the American College of Rheumatology and European League for Rheumatism, and healthy control volunteers (n = 21). They were compared with demographic data, clinical evaluation, and the dosage of metals in the saliva and urine by the Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Results SjD patients exhibited higher urinary excretion of Ag, Hg, Mn, Pt, Sb, Sn, and U, while Al, Se, and Mg were lower (p < 0.05). In saliva, 16 metals had higher levels in SjD: Al, As, Be, Ca, Cd, Co, Cu, Fe, Hg, Mn, Mo, Pb, Sb, U, W, and Zn (p < 0.05). Correlational analysis showed that Cu and Sb in saliva correlated with higher OSDI score (r = 0.55, p = 0.0002, 95%CI 0.28–0.75 and r = 0.34, p = 0.026, 95%CI 0.04–0.59, respectively), As and Cu in saliva with lower salivary flow (r=-0.56, p < 0.0001, 95%CI -0.74– -0.30 and r=-0.41, p = 0.007, 95%CI − 0.64– -0.11, respectively) and urinary Sn and salivary As and Zn were associated with higher corneal staining score (r = 0.40, p = 0.010, 95%CI 0.095–0.635, r = 0.35, p = 0.0025, 95%CI 0.37–0.6 and r = 0.33, p = 0.038, 95%CI 0.01–0.58, respectively). Conclusions Metal levels in saliva and urine were significantly different between SjD and healthy individuals. Antimony, arsenic, copper, tin, and zinc presented correlations with SjD clinical findings, suggesting that environmental metal exposure may influence disease manifestations in SjD.