LAUSR

The purpose of our study was to investigate the association between olfactory function in Parkinson's disease (PD) and serum vitamin D status. Thirty-nine patients with de novo PD were enrolled in this study. Olfactory function was assessed by an odor identification test, as a part of the KVSS (Korean version of sniffin' sticks) II test. All patients were also assessed with the NMSS (Non-Motor Symptoms Scale for PD) to check the subjective change in ability to smell. Vitamin D status was determined by measuring the level of serum 25-hydroxyvitamin D3 (25-OHD3). Multiple linear regression tests and correlation analysis were applied to verify the association between serum 25-OHD3 level and patients' subjective and objective olfactory dysfunction. The serum 25-OHD3 level was independently associated with odor identification score in patients with PD (β = 0.38, p < 0.01). Another statistically significant variable was clinical subtype of PD (Intermediate subtype: β = -0.33, p < 0.05; Akinetic rigid type: β = -0.55, p < 0.01). The serum 25-OHD3 level was also negatively correlated with the score for item number 28 in NMSS (Spearman's rho = -0.32, p < 0.05). Our results showed that vitamin D status might be an independent factor for olfactory dysfunction in PD. Although the underlying mechanism has not been clearly identified, we postulate that vitamin D plays a role in the pathogenesis of olfactory dysfunction in PD. Further investigation to elucidate the precise relationship of vitamin D to PD is essential.