J Neurol Neurosurg Psychiatry 76:1342-1347 doi:10.1136/jnnp.2003.032003
  • Paper

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

  1. J M Olichney1,
  2. C Murphy2,
  3. C R Hofstetter1,
  4. K Foster1,
  5. L A Hansen3,
  6. L J Thal1,
  7. R Katzman1
  1. 1Alzheimer’s Disease Research Center, University of California, San Diego, California, USA
  2. 2Department of Psychology, San Diego State University
  3. 3Department of Pathology, University of California, San Diego
  1. Correspondence to:
 Dr John M Olichney
 Neurology Service (9127), VA San Diego Healthcare System, 3350 La Jolla Village Drive, San Diego, CA 92161, USA;
  • Received 26 January 2004
  • Accepted 16 January 2005
  • Revised 14 January 2005


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.


  • Competing interests: none declared

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