Olfactory dysfunction in aging and neurodegenerative diseases

Alterations in olfactory functions are proposed to be early biomarkers for neurodegeneration. Many neurode-generative diseases are age-related, including two of the most common, Parkinson's disease (PD) and Alz-heimer's disease (AD). The establishment of biomarkers that promote early risk identification is critical for the implementation of early treatment to postpone or avert pathological development. Olfactory dysfunction (OD) is seen in 90% of early-stage PD patients and 85% of patients with early-stage AD, which makes it an attractive biomarker for early diagnosis of these diseases. Here, we systematically review widely applied smelling tests available for humans as well as olfaction assessments performed in some animal models and the relationships between OD and normal aging, PD, AD, and other conditions. The utility of OD as a biomarker for neurode-generative disease diagnosis and future research directions are also discussed.

Automated summary

This study explores alterations in olfactory functions as early biomarkers for neurodegeneration, particularly in early-stage Parkinson's and Alzheimer's disease. Implementing early treatment to postpone or avert pathological development is crucial for these diseases.