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Odor Tests Could Help Detect Early Alzheimer's Disease, New Study Suggests

A recent clinical research study, published in the journal Neurology, found that odor identification may be linked to early Alzheimer’s disease (AD).

Early Alzheimer’s Disease

During the preclinical stage of AD, no symptoms have yet started.  Although, minor lapses of memory are a normal part of the aging process, gradual decline in memory is a hallmark sign of AD.  This type of memory loss differs from normal aging in that forgotten memories cannot usually be retrieved at a later point in time.  With normal age-related memory loss, the forgotten incident, name or other factor, can usually be remembered at some point.
It is estimated that the symptoms may actually start in the brain decades before any type of memory loss or other signs of AD are observed.  Because of this, many recent medical science research projects focus on early detection and intervention, before memory loss begins.

The Study

A recent study called, “Odor identification as a biomarker of preclinical AD in older adults at risk.” was conduced by John Breitner, M.D., director of the Center for Studies on Prevention of Alzheimer’s disease, at the Douglas Mental Health Research Center of McGill University, and lead author of the study.  Breitner commented in a recent press release, “Despite all the research in the area, no effective treatment has yet been found for Alzheimer’s disease.  But, if we can delay the onset of symptoms by just five years, we should be able to reduce the prevalence and severity of these symptoms by more than 50%.”

The study involved 274 healthy participants, approximately 63 in age.  The participants all had a family history of AD.  In the study, researchers looked at the connection between preclinical AD and odor identification in study participants, using scratch and sniff tests.  The scents included, lemon, bubble gum or gasoline.  The level of abnormal AD related protein in the cerebro-spinal fluid was identified in 101 participants.

Study Conclusion

The results concluded that those with a reduced ability to identify the odors had a higher incidence of AD biomarkers called tau proteins’s (a hallmark symptom of AD).  This lower level of odor identification was also linked to cognitive decline and increase in age.

Marie-Elyse Lafaille-Magnan, the study’s first author and a doctoral student at McGill, said the research indicates, “that the loss of the ability to identify smells is correlated with biological markers indicating the advance of the disease.”  Lafaille-Magnan also stated, “For more than 30 years, scientists have been exploring the connection between memory loss and the difficulty that patients may have in identifying different odors. This makes sense, because it’s known that the olfactory bulb (involved with the sense of smell) and the entorhinal cortex (involved with memory and naming of odors) are among the first brain structures to be affected by the disease.”

It’s important to note that the loss of the ability to smell odors is not always associated with AD and may be a result of other medical conditions.  More research is needed to determine just how the altered ability to identify odors correctly is related to early Alzheimer’s disease.

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