Olfactory screening test in mild cognitive impairment.

Mild cognitive impairment (MCI) is a transient status between physiologic ageing and dementia. Each year more than 12% of subjects with MCI develop Alzheimer's disease. This study evaluated the presence of an olfactory deficit in amnesic MCI (aMCI) patients. Twenty-nine patients diagnosed with aMCI and a homogeneous control group of 29 subjects were enrolled in the study. Olfactory function was assessed by the Sniffin' Sticks Screening Test (SSST) and the Mini Mental State Examination, the Clinical Dementia Rating, the Geriatric Depression Scale and the Mental Deterioration Battery were used to evaluate the neurocognitive status. aMCI patients showed a significant impairment of their olfactory identification compared to controls (SSST score: 8.3+/-2.1 vs. 10.8+/-0.9; p<0.001). These results suggest that olfactory tests should be part of the diagnostic armamentarium of pre-clinical dementia. A long-term follow up might confirm the olfactory identification function as an early and reliable marker in the diagnosis of pre-clinical dementia.