Measurement of sensitivity to olfactory flavor: application in a study of aging and dentures

Olfaction involves a dual sensory process for perceiving odors orthonasally (through the nostrils) and retronasally (through the mouth). This investigation entailed developing a measure of sensitivity to an odor delivered in an orally sampled food (orange flavoring in a sucrose-sweetened gelatin) and examining sensitivity in the elderly. In experiment 1, olfactory flavor sensitivity was 49 times lower in elderly (n = 21) than in young (n = 28) subjects. In experiment 2, with 73 elderly women, higher olfactory flavor sensitivity correlated significantly with higher orthonasal perception (Connecticut Chemosensory Clinical Research Center test). Some women, however, exhibited low olfactory flavor sensitivity despite high orthonasal perception; none had high olfactory flavor sensitivity and low orthonasal perception. Those who wore complete or palatal covering dentures had lower olfactory flavor sensitivity than those who were dentate or wore dentures that did not cover the palate. Through multiple regression analysis, orthonasal perception and denture status were found to be independent contributors to predicting olfactory flavor sensitivity. In summary, elderly subjects showed depressed olfactory flavor sensitivity (i.e. retronasal sensitivity) that related to poor orthonasal olfactory perception and denture characteristic. Thus, while good orthonasal olfaction may be necessary for good olfactory flavor sensitivity, it is not sufficient. Other factors, some associated with oral conditions, may impede release and retronasal transport of odors from the mouth to the olfactory receptors.