[Sense of smell, physiological ageing and neurodegenerative diseases: II. Ageing and neurodegenerative diseases]

Abstract

Introduction: The sense of smell, which was once studied because of its biological and evolutionary significance, is today one of the centres of interest in research on normal and pathological ageing. The latest scientific developments point to an inversely proportional relationship between age and olfactory sensitivity. In certain neurodegenerative diseases this sensory decline is one of the first symptoms of the disorder and is correlated with the progression of the disease.

Development: In this work we are going to review the scientific knowledge on loss of sense of smell in ageing and in neurodegenerative diseases, with special attention given to Alzheimer's and Parkinson's diseases.

Conclusions: A survey of studies that have examined the olfactory deficits in ageing and in some neurodegenerative diseases offers conclusive results about the presence of these impairments in the early stages of these disorders and even among healthy elderly persons. Although a number of causes contribute to these sensory losses in physiological ageing, a common neurological foundation has been proposed for Alzheimer's and Parkinson's diseases. Nevertheless, despite certain initial similarities, the olfactory deficits shown in these disorders seem to be qualitatively different.