AGING EFFECT: The effect of aging on the olfactory system is generally observed in subjects over the age of 65 and is the number one cause of olfactory disorders. Several studies taking into account the state of the naso-sinus system and possible early stage of developing dementia have examined the precise effects of aging on olfaction. AGE-RELATED CHANGES: Aging affects olfactory thresholds, estimation of the intensity of an olfactory stimulation, and identification and memorization of odors. The elderly subject identifies food and other odors less easily than the young subject although elderly subjects can learn to improve their performance. Changes in the nasal cavity, particularly an alteration of the processes involved in neuron distribution in the olfactory neuroepithelium, may be involved. IMPACT OF OLFACTORY DEFICIENCY: There is much morphological and experimental evidence showing the effect of aging on both peripheral and central olfactory pathways allowing a better understanding of the functional impact of the sensorial deficit. Olfactory deficiency can explain in part the eating problems encountered in elderly patients.