Smelling Parkinson’s Disease: New Metabolomic Biomarker for PD

Parkinson’s disease (PD) is the second most common neurodegenerative disease after Alzheimer’s disease (AD) with an estimated 6 million people affected worldwide. Numbers are expected to double over the next generation,1 motivating research in the development of biomarkers for early detection, like that reported by Barran and co-workers.2 PD is characterized by a combination of classical motor abnormalities, including a characteristic bilateral or asymmetric rest tremor (most commonly affecting the upper limbs initially), combined with muscular rigidity and a peculiar type of loss of speed and amplitude of voluntary movements. These motor abnormalities are accompanied by a variety of nonmotor symptoms in a majority of patients. These nonmotor symptoms include a decreased sense of smell, constipation, disorders of the sleep–wake-cycle (rapid eye movement sleep behavior disorder, RBD, being the most characteristic for PD), anxiety, depression, and cognitive dysfunction