Age-Related Changes In Resposiveness Of The Olfactory Epithelium

Olfactory impairment in aging adults  is probably  due to many causes, including structural changes at the level of the olfactory mucosa. Aim of the present investigation was to study age-related changes in response to olfactory and trigeminal stimuli at the level of the olfactory mucosa and the central nervous system, using electrophysiological responses. A total of 73 participants were examined (younger: n=40, 18-27 years; older: n=33, 50-78 years). All subjects received nasal endoscopy, a standardized medical history, and detailed olfactory testing (Sniffin Sticks). For intranasal stimulation olfactory (H2S, PEA) and trigeminal (CO2) stimuli were used. Stimuli of 500 ms duration were embedded in a constant airflow of ~8l/min using air-dilution olfactometry. Responses were recorded from the olfactory epithelium (electro-olfactograms, EOG). Simultaneously, EEG-derived olfactory event-related potentials (OERP) were analyzed. Results from psychophysical olfactory tests were negatively correlated with the age of the participants (r=-0.42, p<0.001). Although EOG amplitudes and latencies did not show an age-related difference, younger individuals showed significantly more EOG responses than older ones. For the central-nervous OERP response latencies were significantly shorter in younger participants than in older ones. OERP amplitudes were significantly different between age groups. However, the number of detectable OERP responses was smaller in older participants. In conclusion, the present results showed small age-related differences between a younger and an older group, both at peripheral and central-nervous levels. The present results indicate relatively small changes in the processing of olfactory information possibly pointing at redundancies in the system or the effectivity of compensatory mechanisms.