Age-Related Olfactory Dysfunction: Epidemiology, Pathophysiology, and Clinical Management

Area of Science:

• Neuroscience
• Gerontology
• Sensory Systems Biology

Background:

• Olfactory function declines with age, with higher incidence in individuals over 60 and males.
• Risk factors include smoking, heavy alcohol use, sinonasal diseases, and Down's syndrome.
• Aging impacts both peripheral and central olfactory systems, affecting olfactory neuroepithelium and olfactory bulb (OB) interneuron turnover.

Purpose of the Study:

• To review the effects of aging on the olfactory system.
• To explore the link between olfactory dysfunction and neurodegenerative diseases like Alzheimer's disease (AD) and Parkinson's disease (PD).
• To discuss potential therapeutic strategies for age-related olfactory dysfunction.

Main Methods:

• Review of epidemiological studies on olfactory dysfunction.
• Analysis of animal studies on aging's effects on the peripheral and central olfactory nervous systems.
• Examination of recent research on olfactory impairment and neurodegenerative diseases.

Main Results:

• Aged olfactory neuroepithelium exhibits loss of mature olfactory neurons and reduced basal cell proliferation.
• Central olfactory pathways show decreased interneuron turnover in the OB and reduced olfactory cortex activity.
• A growing body of evidence links olfactory impairment to AD and PD.

Conclusions:

• Age-related olfactory dysfunction involves significant changes in both peripheral and central olfactory structures.
• Olfactory impairment is increasingly recognized as a potential early indicator of neurodegenerative diseases.
• Currently, no definitive pharmacotherapy exists, but olfactory training may offer a viable approach to improve olfactory function.