Lateralized and Overall Olfactory Identification Ability in Frontotemporal Dementia and Alzheimer\u27s Disease

Abstract

This research involves an examination of the olfactory ability of individuals with Frontotemporal Dementia, Alzheimer\u27s disease, and geriatric individuals with cognitive complaints owing to Major Depressive Disorder or Generalized Anxiety Disorder. The purpose of this study was to determine if olfactory differences were useful in differentiating between demented and non-demented individuals. Due to the pathway of the olfactory tract, it can be expected that there would be equal olfactory deficits in those diagnosed with Frontotemporal Dementia and Alzheimer\u27s disease, and that these deficits would be worse than those found in geriatric individuals with Major Depressive Disorder or Generalized Anxiety Disorder. Five hypotheses were investigated. The first utilized an ANCOVA and found that the olfaction of the demented group was worse than that of the non-demented, psychiatric group. The second utilized a series of Discriminant Function Analyses and F-tests and determined that olfaction best classified demented and non-demented individuals. The third implemented a Mixed Model ANOVA to assess for lateralized smell deficits within the demented group and between the demented and non-demented groups and found no main effects of lateralization or interaction effects. The fourth hypothesis investigated the relationship between smell and commonly used neuropsychological tests in a Frontotemporal Dementia sample, and found that there was no difference between the relationship of tests measuring the frontal and temporal lobes to those measuring other cerebral areas. The fifth hypothesis replicated Hypothesis 4 in an Alzheimer\u27s disease sample and found that there was a significant difference between the relationship of tests measuring the frontal and temporal lobes to those measuring other cerebral areas. Primarily, this study demonstrated that dementia patients present with significantly more olfactory deficits than a psychiatric sample with subjective cognitive complaints. Additionally, olfaction correctly distinguished the Dementia Group from the Psychiatric Group with 81.6% accuracy, 90.2% sensitivity and 67.6% specificity. Alone, these classification statistics are quite impressive, appearing equivalent, or possibly superior to the classification statistics of commonly used neuropsychological tests of memory, executive functioning, and visuospatial ability. This study concluded that adding an olfactory measure to an assessment battery provides clinically relevant data, and enhances the diagnostic accuracy of the battery. However, though this study found the Alberta Smell Test was a valuable addition to a test battery, the absence of lateralized findings demonstrated the unirhinal format, by which the Alberta Smell Test is administered, does not provide diagnostically relevant information above and beyond the information a clinician will gain from birhinal assessment