Smell loss has been found to be associated with mortality and neurodegenerative diseases. Unfortunately, there are no current biomarkers for olfactory loss and no specific mechanism to explain exactly how this association occurs. This study aims to uncover more about smell loss and its association with neurodegenerative disease such as Parkinson's disease, Alzheimer's disease, Multiple Sclerosis, and Mild Cognitive Impairment in the early/mild stages of those conditions. Study procedures involve questionnaires, a 40-item scratch and sniff smell test, assessment of cognitive function, blood sample, and nasal mucus and cell samples collected by a physician.

Smell loss has been reported in more than 50% of older adults. Currently there are no validated methods for classifying patients with smell loss in aging based on either disease site or process. This study aims to better understand how age affects the sense of smell. This study will involve those 50 and older and will take up to 5 years, with 5 follow up annual visits, or can be done remotely.