Suprathreshold odor intensity perception in early-stage Parkinson's disease

Background: Whether Parkinson's disease (PD) influences suprathreshold changes in perceived odor intensity is unknown. In patients with Alzheimer's disease, patients with schizophrenia, and the elderly, such perception is reportedly normal. If generally true, this could reflect a core element of the olfactory system insulated to some degree from age- and disease-related pathological conditions. Methods: Odor intensity ratings for pentyl acetate were obtained from 29 early-stage PD patients when on and off dopamine-related medications (DRMs) and from 29 matched controls. Results: The ratings were significantly attenuated at the higher odorant concentrations, with the degree of attenuation associated with overall olfactory dysfunction. Ratings were higher on the right than on the left side of the nose of both patients and controls. No associations with DRMs, Unified Parkinson's Disease Rating Scale (UPDRS) scores, or striatal dopamine transporter imaging were found. Conclusions: Parkinson's disease (PD) influences suprathreshold estimates of perceived odor intensity, negating the notion that such perception might be spared in this disease. No association with dopaminergic processes was apparent.