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Description
Alzheimer’s (AD) is a neurodegenerative disease that is characterized by significant declines in memory functions. Often patients will pass through a transition stage from healthy aging known as mild cognitive impairment (MCI). Pronounced differences in olfactory functioning have been found between normal controls (NC), MCI, and AD patients, suggesting potential for olfactory function to serve as a biomarker for development of AD. Some odor measures have been implicated in the conversion from one stage to the next, however this relationship has not been established for odor memory. This study explored the relationship between odor memory and subsequent conversion from healthy aging to MCI to Alzheimer’s disease. An archival sample of 498 participants from the Alzheimer’s Disease Research Center was used in the analysis. Participants were classified as: NC, MCI, AD and those who converted during the progression of the disease (i.e. NC to MCI). Apo ε4 status, a genetic risk factor for AD, was determined for each participant and used in the analysis. This study used odor memory variables such as: hits, misses, correct rejections and false alarms. Odor familiarity, ID and threshold were included in the analysis. We hypothesized that: each of these odor measures will be able to detect stage changes as well as be more sensitive and specific than the mini-mental status exam (MMSE). Receiver operating characteristic (ROC) curves were analyzed in order to determine the area identifying each condition (i.e. NC to MCI). This allows for the prediction of conversion to AD. We found that, on average, odor memory measures were more effective in predicting the conversion between states than the MMSE and that these effects were particularly pronounced in those genetically at risk for AD (Apo ε4+). Odor familiarity and identification together, along with genetic status, was the most reliable measure of AD. From these results we were able to establish cut off scores that indicate a potential transition between states. This study suggests that odor memory may be a useful screening tool for AD (even in the earliest stages). The benefits are ease of administration, low cost, and early detection for pharmacological intervention.
