OLFACTORY DYSFUNCTION FOR PYRIDINE AND DEMENTIA PROGRESSION IN ALZHEIMER-DISEASE

Objective: To investigate whether odor detection sensitivity for pyrid ine, suggested by previous research not to be affected, is impaired in Alzheimer disease (AD) and whether an association exists between odor threshold and both degree of dementia and rate of dementia progressio n in AD. Method: The method of constant stimuli was used to determine odor thresholds for pyridine in 18 patients with AD (Diagnostic and St atistical Manual of Mental Disorders, Third Edition, Revised and Natio nal Institute of Neurological and Communicative Disorders and Stroke A lzheimer's Disease and Related Disorders Association criteria) and 16 healthy elderly control subjects. All participants were carefully exam ined with medical and neuropsychological tests. Results: Six patients with AD but none of the controls were anosmic (total olfactory loss) t o pyridine, and the 12 nonanosmic patients had significantly higher de tection thresholds (50% probability for detection, 323 parts per billi on [ppb]) than did the controls (50% probability for detection, 105 pp b). In addition, an association was found between odor threshold and b oth degree of dementia and rate of dementia progression in AD. Conclus ions: In contrast to previous findings, our results provide evidence t hat odor sensitivity in AD is impaired for pyridine. Odor sensitivity, in addition to other suggested predictors of progression rate, may be of interest for defining subgroups of AD or for clinical prognostic j udgments of single patients.