A total of 889 patients with olfactory disturbance who were examined at the Olfaction Clinic of Osaka City University Hospital from January 1982 to December 1996 were studied retrospectively using clinical records in order to investigate the relationship between the patient characteristics and prognosis. Etiologically the characteristic variables of head trauma and congenital olfactory disturbance were most strongly associated with poor prognosis. Among patients with rhinosinusitis and head trauma, the characteristic variables of female patients, those with a short period of olfactory disorder, and those with high olfactory acuity before treatment showed faster improvements in olfactory disturbance. None of the characteristic variables had any influence on prognosis in the patients with viral infection. The age and presence of abnormal smell sensations similarly did not have any significant influence on prognosis. Improvement was recognized in most patients within 6 months. Hence, patients with olfactory disturbances should be treated for at least 6 months.
