Olfactory impairment in mild cognitive impairment with Lewy bodies and Alzheimer’s disease

This is the author accepted manuscript. The final version is available from Cambridge University Press via the DOI in this recordObjectives: Impaired olfaction may be a biomarker for early Lewy body disease but its value in Mild Cognitive Impairment with Lewy bodies (MCI-LB) is unknown. We compared olfaction in MCI-LB with MCI due to Alzheimer’s disease (MCI-AD) and healthy older adults. We hypothesised that olfactory function would be worse in probable MCI-LB than in both MCI- AD and healthy comparison subjects (HC). Design: Cross-sectional study assessing olfaction using Sniffin’ Sticks 16 (SS-16) in MCI-LB, MCI- AD and HC with longitudinal follow-up. Differences were adjusted for age and receiver operating characteristic curves were used for discriminating MCI-LB from MCI-AD andHC. Setting: Participants were recruited from Memory Services in the North East of England Participants: 38 probable MCI-LB, 33 MCI-AD, 19 possible MCI-LB and 32HC. Measurements: Olfaction was assessed using SS-16 and a questionnaire. Results: Participants with probable MCI-LB had worse olfaction than both MCI-AD (Age-adjusted mean difference (B)=2.05,95% CI:0.62-3.49, p=.005) and HC (B=3.96, 95% CI:2.51–5.40, p<.001). The previously-identified cut-off score for the SS-16 of ≤ 10 had 84% sensitivity for probable MCI-LB (95% CI: 69-94%) but 30% specificity vs MCI-AD. ROC analysis found a lower cut-off of ≤ 7 was better (63% sensitivity for MCI-LB, with 73% specificity vs MCI-AD and 97% vsHC). Asking about olfactory impairments was not useful in identifying them. Conclusions: MCI-LB had worse olfaction than MCI-AD and normal ageing. A lower cut-off score of ≤ 7 is required when using SS-16 in such patients. Olfactory testing may have value in identifying early LB disease in memory services.Alzheimer’s Research UKNational Institute for Health Research (NIHR