Abstract & Information
Thomas Hummel, M.D.¹, and Steven Nordin, Ph.D.²

¹Smell and Taste Clinic, Department of Otorhinolaryngology, University of Dresden Medical School, Fetscherstrasse 74, 01037 Dresden, Germany; phone 011-49-351-458-4189, fax 011-49-351-4326,

²Department of Psychology, Umea University, 90187 Umea, Sweden

Acknowledgments: We greatly appreciate the help of Drs. Johannes Frasnelli and Basile Landis, Smell and Taste Clinic, Department of Otorhinolaryngology, University of Dresden Medical School, Germany, for thoughtful comments.

Abstract
Loss of olfactory function is frequent. While olfactory loss goes undetected in everyday life in many of these patients, and almost all of them continue their social and professional activities, it may severely alter the quality of life of these people. Problems are typically reported primarily in the areas of safety and eating. Further, olfactory loss produces a feeling of insecurity, for example as one's own body odors are no longer perceived. However, while this issue is often brought up in the literature, surprisingly little systematic research has been done in this area. Only during the last years tools have become available which allow the assessment of changes in quality of life brought about through olfactory disorders. Especially in light of the treatment of olfactory dysfunction, these measures appear to be of special significance.

Introduction
Smell problems can have a significant impact on our lives. When the sense of smell is lost, it is not just that it becomes a difficult task to differentiate between cardboard and a hamburger, but also a sense is lost which alerts us to dangers from fire or rotten food ¹. An even more profound impact becomes apparent considering that this sensory system may even contribute to the selection of a spouse ^2-4. However, having said all this, it is probably the enjoyment of what we eat or drink that is most dearly missed when the sense of smell has been lost.

Disturbances of the chemical senses are frequent. It is estimated that a complete loss of the sense of smell is found in at least 1 % of the US population (⁵; compare ^{6, 7}). In a recent study of individuals aged 53-97 years, 24% were found to have impaired olfactory function ⁸. In addition, each year hundreds of thousands of patients complain to their physician about disturbances of smell or taste ^{9, 10}. This is despite the fact that often olfactory loss appears to go unnoticed ^{10, 11}, even in cases where head trauma caused sudden olfactory loss ¹². Thus, when considering observations in this area of research, the selection bias has to be kept in mind. People with decreased olfactory sensitivity who do not seek counselling are less likely to have a decreased quality of life compared to patients who present themselves actively to specialized centers, where this kind of research is done. Consequently, research in this area will overstate the average impact of olfactory loss.

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