Olfactory dysfunction has been identified as an early symptom of Parkinson disease (PD), and research from Japan now suggests that severe hyposmia predicts cognitive decline in patients with PD. The 3-year longitudinal study involved 44 patients with PD, none of whom had dementia at baseline. The risk of developing dementia during the course of the study was found to increase 18.7-fold for each 1-SD reduction in baseline odor identification scores.