Smell Dysfunction in Patients with Primary Sjögren's Syndrome: Impact on Quality of Life

Patients with primary Sjögren's syndrome (pSS) often report smell and taste disturbances. However, the correlation between smell impairment and mucosal dryness is not well understood. The objectives of this study were to investigate the following: (1) the prevalence of smell hypofunction in patients with SS; (2) the impact of smell hypofunction on their quality of life (QoL); (3) whether the patients' smell is correlated with xerostomia; and (4) whether the patients' smell is affected by taste hypofunction, disease duration, age, smoking or self-reported neuropathy.

An ethically approved cross-sectional study was conducted on 65 female patients with SS and 62 sex-matched healthy controls. Their smell was assessed using the University of Pennsylvania Smell Identification Test. Their taste acuity was assessed using the Taste Strips Test. A visual analogue scale was used for the self-assessment of smell and taste functions. Xerostomia was assessed by the salivary flow rate, clinical oral dryness score and the Xerostomia Inventory. The patients' QoL and mental health well-being were assessed using validated questionnaires.

In the SS group, the patients' smell function was impaired in 27/65 patients compared with the controls (15/62, p < 0.05), and it did not correlate with the severity of xerostomia, taste acuity (r = 0.05, p = 0.6) or self-reported nasal dryness (r = -0.02, p = 0.7). In the patients' group, smell hypofunction was not correlated with disease duration (β = 0.1, 95% CI = -0.07-0.1) or smoking (β = -0.02, 95% CI = -8-7). Age was not correlated with the smell function in the patients' group (β = -0.1, p = 0.5) but was correlated significantly with smell in the healthy participants' group (β = -0.3, p = 0.02). Neuropathy affected 81.2% of the patients' group. Their QoL and mental health well-being were not affected by smell hypofunction.

Smell hypofunction appears to be a clinical manifestation in patients with SS, but it does not seem to be associated with the severity of mucosal dryness or with taste disturbance.