Factors associated with Parkinson's disease patients with hyposmia in Chines e han population: a case-control study

Background: Hyposmia is important for early and differential diagnosis of Parkinson's Disease (PD); however its mechanism remains unclear. The aim of this retrospective study is to identify the clinical phenotypic associated with hyposmia in Chinese han PD patients. Methods: We used 16-item odor identification test from Sniffin’ Sticks (SS-16) to evaluate the olfactory function of 120 Chinese Han PD patients (including 62 PD patients without hyposmia (PDOH) and 58 PD patients with hyposmia (PDH) and compared them with 60 Healthy Controls (HC). We analyzed the correlation between hyposmia with disease related characteristics including motor symptoms (TremorDominant (TD) type and Postural Instability and Gait Difficulty (PIGD) type) and other common NonMotor Symptoms (NMSs) (constipation, depression and level of serum uric acid). Results: Compared to HC, constipation, depression and level of serum uric acid showed significant difference in PDH (χ2=37.465, P=9.3E10; tD=4.32, P=0.005; tD=3.742, P=0.01, respectively) or PDOH (χ2=17.391, P=3.0E5; tD=4.166, P=0.006; tD=2.780, P=0.03, respectively). Constipationwas significantly associated with PDH compared to PDOH (χ2=5.534, P=0.02), while depression and level of serum uric acid were negative(tD=0.162, P=0.89; tD=0.961, P=0.37, respectively). Patients with TD type was significantly more than those with PIGD type between PDH and PDOH (χ2=6.487, P=0.01). Conclusions: Tremor-dominant type and constipation may be associated with hyposmia in Chinese han PD patients, not depression and level of serum uric acid.