Serum vitamin D level is associated with smell dysfunction independently of aeroallergen sensitization, nasal obstruction, and the presence of allergic rhinitis in children.

Background: Smell dysfunction is highly prevalent worldwide and has adverse effects on quality of life. Smell loss in rhinitis subjects is mainly caused by mechanical obstruction of odorant transmission due to mucosal type 2 inflammation. We determined the association of 25-hydroxyvitamin D (25[OH]D) levels with the severity of smell dysfunction in children.

Methods: We measured the olfactory threshold score in a total of 518 children (10-12 years old, 264 boys) using the Sniffin' Sticks kit, and the children were divided into tertiles according to olfactory threshold score. We also assessed serum 25[OH]D level, common aeroallergen-specific immunoglobulin E, rhinitis severity with visual analog scale, and the Total Four Symptom Score, and pre- and post-decongestant nasal patency with acoustic rhinometry.

Results: The children with 25(OH)D deficiency had significantly reduced mean olfactory threshold scores when compared to those with 25(OH)D levels of ≥20.0 ng/mL (6.56 ± 3.54 and 7.28 ± 3.87, respectively, P = .036). The proportion of loss of smell function and pre-decongestant nasal patency significantly associated with low 25(OH)D levels (chi-square trend test, P for trend = .007). Likewise, after adjustment for confounders, children with smell loss (third tertile) were significantly associated with low 25(OH)D level (aβ=-0.062, 95% CI=-0.064 to -0.060, P = .009) independent of aeroallergen sensitization, and a low pre-decongestant nasal patency.

Conclusions: 25-Hydroxyvitamin D is significantly associated with smell dysfunction independent of aeroallergen sensitization, nasal obstruction, and the presence of allergic rhinitis. This finding may provide insight into the mechanisms involved in the development of olfactory dysfunction.