Olfaction deterioration in cognitive disorders in the elderly

Parkinson's and Alzheimer's diseases are widespread neurodegenerative pathologies. Parkinson's disease affects about 1 % of the population over the age of 65 years, while Alzheimer is considered the most common cause of dementia, with an annual incidence of 1 % in persons aged 65 years. It has been demonstrated that both these neurodegenerative diseases are associated with smell dysfunction. The aim of the present review is to describe briefly modern olfactory evaluation tools as well as the importance of olfactory sensitivity screening in the elderly, especially where cognitive disorders, such as Alzheimer's or Parkinson's diseases, are suspected. A brief literature review focusing on the basic principle of smell tests is illustrated together with their application in elderly patients affected by cognitive disorders, in particular Parkinson's and Alzheimer's diseases. Alzheimer's and Parkinson's diseases are both neurodegenerative disorders typically found in the elderly. As both diseases are characterized by the early presence of dysosmia, simple validated smell tests could very well help clinicians in the early diagnosis of these neuropathological conditions. Elderly patients complaining of smell loss and found to be dysosmic, by means of validated olfactory tests, should be neurologically evaluated as early as possible to detect slight motor abnormalities in an at-risk population.