Vol.:(0123456789) 1 3 Journal of Neurology https://doi.org/10.1007/s00415-019-09551-2 ORIGINAL COMMUNICATION Sex‑related diferences in olfactory function and evaluation of possible confounding factors among patients with Parkinson’s disease P. Solla 1  · C. Masala 2  · A. Liscia 2  · R. Piras 2  · T. Ercoli 1  · L. Fadda 1  · T. Hummel 3  · A. Haenher 3  · G. Defazio 1 Received: 28 June 2019 / Revised: 18 September 2019 / Accepted: 19 September 2019 © Springer-Verlag GmbH Germany, part of Springer Nature 2019 Abstract The role of specifc sex-related patterns in olfactory dysfunctions of Parkinson’s disease (PD) patients is unclear. The aim of this study was to assess the presence of specifc sex-related patterns in olfactory dysfunctions excluding the possibility of confounding efects in patients with Parkinson’s disease. One hundred and sixty-eight participants (99 PD patients and 69 controls) were enrolled and evaluated using Snifn’ Sticks Extended test (SSET). There was no signifcant sex diference in the control group for the SSET parameters. By contrast, in the PD group male patients scored signifcantly lower on odor discrimination (OD), identifcation (OI), and Threshold-Discrimination-Identifcation (TDI) score than females. On multivari- able linear regression analysis, the only signifcant predictors of TDI score were sex and apathy. Among PD patients, men showed a signifcantly greater impairment compared to women in OI, OD and TDI score, but not in odor threshold (OT). These fndings highlighted the possible role of sex diferences in the development of associated PD non-motor symptoms. Keywords Parkinson’s disease · Olfaction · Sex diferences · Non-motor symptoms Introduction Olfactory dysfunction is a frequent non-motor feature of idi- opathic Parkinson’s disease (PD) [1, 2] that may also pre- cede disease onset [3–6]. Probably, hyposmia is not merely due to loss of dopaminergic neurons in the olfactory bulb [7] and central mechanisms are likely involved. Supporting this view, a recent study showed that an impairment in odor identifcation (OI) and in odor discrimination (OD) were associated with both apathy and severity of motor symptoms [8]. Sex-related diferences regarding motor and non-motor symptoms (NMS) in PD patients [9] constitute an interest- ing topic in biomedical research [10–13], although this is relatively under-investigated. In fact, the identifcation of possible diferences between sexes may have signifcant implications both for the susceptibility to develop this neu- rodegenerative disease and for the clinical and therapeutic management of the afected patients. In the last years, sev- eral researchers have also investigated the possible infuence of sex on hyposmia in PD, but results were inconsistent. Recently, Melis and Colleagues [14] suggested that sex may have an efect on the impairment of olfactory performance in PD patients and identifed the odorant-binding protein IIa (OBPIIa) gene locus. Greater smelling difculties were sometimes reported in women [15], while other studies in PD patients observed that men performed signifcantly worse than women [16–21]. Previous studies [16–21] assessed olfactory function using different clinical tools, but did not check for possible confounding factors in the relationships between sex and olfaction. In this study, we investigated possible sex-related difer- ence in olfactory function in PD patients and controls by P. Solla and C. Masala have contributed equally to this work. * P. Solla paosol29@yahoo.it * C. Masala cmasala@unica.it 1 Department of Neurology, Movement Disorders Center, Institute of Neurology, Azienda Ospedaliero Universitaria (A.O.U.), University of Cagliari, Cagliari, Italy 2 Section of Physiology, Department of Biomedical Sciences, University of Cagliari, Cagliari, Italy 3 Department of Otorhinolaryngology, Medical Faculty Carl Gustav Carus, Interdisciplinary Center Smell and Taste, TU Dresden, Dresden, Germany