Olfactory dysfunction in aging and neurodegenerative diseases

Ageing Res Rev. 2021 Sep:70:101416. doi: 10.1016/j.arr.2021.101416. Epub 2021 Jul 27.


Alterations in olfactory functions are proposed to be early biomarkers for neurodegeneration. Many neurodegenerative diseases are age-related, including two of the most common, Parkinson's disease (PD) and Alzheimer'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 neurodegenerative disease diagnosis and future research directions are also discussed.

Keywords: Aging; Alzheimer’s disease; Neurodegeneration; Olfactory dysfunction; Parkinson’s disease.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, N.I.H., Intramural
  • Review
  • Systematic Review

MeSH terms

  • Aging
  • Alzheimer Disease* / diagnosis
  • Animals
  • Humans
  • Neurodegenerative Diseases*
  • Olfaction Disorders* / diagnosis
  • Parkinson Disease*
  • Smell