Anosmia is very common in the Lewy body variant of Alzheimer's disease

John M Olichney, C. Murphy, C. R. Hofstetter, K. Foster, L. A. Hansen, L. J. Thal, R. Katzman

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Abstract

Background: Olfactory abnormalities are reported in Alzheimer's disease and Parkinson's disease. Anosmia appears to be common in dementia with Lewy bodies but not in pure Alzheimer's disease. Objective: to determine whether anosmia improves discrimination between the Lewy body variant (LBV) of Alzheimer's disease and "pure" Alzheimer's disease. Methods: 106 cases of necropsy confirmed pure Alzheimer's disease (n = 89) or LBV (n = 17) were reviewed. All had received butanol odour threshold testing. Anosmia was defined as a score ≤ 1.0 on a 0-9 point scale. Logistic regression analysis was used to model potential predictors (for example, parkinsonism, smoking, hallucinations) of neuropathological diagnosis and anosmia. Results: LBV cases had an increased prevalence of anosmia (65%) compared with Alzheimer's disease (23%; odds ratio (OR) = 6.3, p = 0.00045), or normal elderly people (6.7%). Within the dementia cases, the negative predictive value (92%) and specificity (78%) of anosmia were both good; sensitivity for detecting LBV was 65%, but the positive predictive value (PPV) was only 35%. Logistic regression models showed anosmia (OR = 5.4, p = 0.005) and visual hallucinations (OR = 7.3, p = 0.007) were strong independent predictors of Lewy body pathology. When anosmia was added as a core feature to consensus diagnostic criteria for probable Lewy body dementia, five additional cases of LBV were detected (29% increased sensitivity), but with four additional false positives (1% increased discrimination, 4% decreased specificity, 33% decreased PPV). Conclusions: Anosmia is very common in LBV. Adding anosmia as a core feature improved sensitivity for detecting LBV, but did not improve discrimination between Alzheimer's disease and LBV owing to a concomitant increase in false positives.

Original languageEnglish (US)
Pages (from-to)1342-1347
Number of pages6
JournalJournal of Neurology, Neurosurgery and Psychiatry
Volume76
Issue number10
DOIs
StatePublished - Oct 2005

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ASJC Scopus subject areas

  • Neuropsychology and Physiological Psychology
  • Neuroscience(all)
  • Psychiatry and Mental health

Cite this

Olichney, J. M., Murphy, C., Hofstetter, C. R., Foster, K., Hansen, L. A., Thal, L. J., & Katzman, R. (2005). Anosmia is very common in the Lewy body variant of Alzheimer's disease. Journal of Neurology, Neurosurgery and Psychiatry, 76(10), 1342-1347. https://doi.org/10.1136/jnnp.2003.032003