Impaired sense of smell may be early indicator of Parkinson's disease

Impaired sense of smell occurs in the earliest stages of Parkinson’s disease (PD) and there is mounting evidence that it may precede motor symptoms by several years, although no large-scale studies had confirmed this. In the first study involving the general population, researchers found that smell impairment can precede the development of PD in men by at least four years. The study is published in the Annals of Neurology.