Learning about the functions of the olfactory system from people without a sense of smell

Abstract

The olfactory system provides numerous functions to humans, influencing ingestive behavior, awareness of environmental hazards and social communication. Approximately 1/5 of the general population exhibit an impaired sense of smell. However, in contrast to the many affected, only few patients complain of their impairment. So how important is it for humans to have an intact sense of smell? Or is it even dispensable, at least in the Western world? To investigate this, we compared 32 patients, who were born without a sense of smell (isolated congenital anosmia--ICA) with 36 age-matched controls. A broad questionnaire was used, containing domains relevant to olfaction in daily life, along with a questionnaire about social relationships and the BDI-questionnaire. ICA-patients differed only slightly from controls in functions of daily life related to olfaction. These differences included enhanced social insecurity, increased risk for depressive symptoms and increased risk for household accidents. In these domains the sense of olfaction seems to play a key role.

Figure 1. Structural magnetic resonance image of an isolated congenital anosmic patient (left).

Within the marked region an olfactory bulb is missing. This becomes obvious compared to the healthy person visualized in the right picture.

Figure 2. Comparison of ICA-patients (N = 32) and age-matched controls (N = 36) with regard to eating behavior, washing behavior, household accidents and social insecurity.

The bars visualize the mean ratings for the scales; error bars indicate the single standard deviation. ICA-patients significantly more often agreed to have household accidents and to be unsure in certain social situations.

Figure 3. Comparison of the number of sexual relationships in ICA-patients (N = 32) and age-matched controls (N = 40).

Controls report to have had significantly more different sexual partners than ICA-patients.