Salivary cortisol as a neuroendocrine stress biomarker for xerostomia in multiple sclerosis patients: a comparative cross-sectional study

BACKGROUND: Xerostomia is a common and clinically relevant complaint in patients with multiple sclerosis (MS), adversely affecting oral health, nutrition, and the quality of life. Neuroendocrine and autonomic dysregulation associated with MS may contribute to salivary gland dysfunction. It was hypothesized that MS patients with xerostomia would indicate higher salivary cortisol levels compared to individuals without xerostomia, the independent of self-reported anxiety. METHODS: In this comparative cross-sectional study, 39 MS patients were enrolled, including 23 with xerostomia and 16 without. Demographic characteristics, medication use, salivary cortisol concentrations, xerostomia severity, and anxiety levels were assessed. Unstimulated whole saliva was collected using the spitting method, and cortisol levels were quantified by enzyme-linked immunosorbent assay (ELISA). Furthermore, xerostomia was evaluated clinically using the Abslang test and subjectively using the Short Xerostomia Inventory (SXI). Anxiety was also assessed using the Beck Anxiety Inventory (BAI). RESULTS: No significant differences were observed between the groups in terms of age, gender, medication use, or other assessed confounding factors. The patients with xerostomia demonstrated significantly higher salivary cortisol levels than controls (8.5 ± 1.8 vs. 4.7 ± 2.2 ng/mL, p = 0.045) and greater xerostomia severity scores (7.10 ± 2.20 vs. 2.80 ± 1.50, p = 0.001). In contrast, the anxiety scores were significantly lower in the xerostomia group compared with the controls (11.77 ± 8.30 vs. 17.23 ± 10.21, p = 0.03). CONCLUSIONS: Salivary cortisol levels were associated with the presence and severity of xerostomia in MS patients, despite lower self-reported anxiety levels. This lack of association demonstrates that salivary cortisol may reflect physiological stress or neuroendocrine/autonomic dysregulation rather than subjective anxiety alone. While causality cannot be inferred due to the cross-sectional design, these findings support the potential role of salivary cortisol as a biomarker for xerostomia in MS and provide the importance of integrating biological stress markers into oral health assessment in this population.