According to a recent study, individuals carrying the APOE e4 gene variant associated with an increased risk of Alzheimer’s disease might experience an early loss of smell detection ability.
This could potentially serve as an early indication of future cognitive and memory issues. The study’s findings were published in the online issue of Neurology on July 26, 2023.
Study Findings and Implications
“Testing a person’s ability to detect odors may be a useful way to predict future problems with cognition,” stated study author Matthew S. GoodSmith, MD, of the University of Chicago.
“While more research is needed to confirm these findings and determine what level of smell loss would predict future risk, these results could be promising, especially in studies aiming to identify people at risk for dementia early in the disease.”
The research involved an at-home survey that tested the olfactory capabilities of over 865 individuals. Their ability to detect and identify smells were tested at five-year intervals.
Additionally, participants’ thinking and memory skills were assessed twice, five years apart.
People carrying the APOE e4 gene variant were found to be 37% less likely to have good odor detection compared to individuals without the gene at a single timepoint. This reduction in smell detection typically began around the ages of 65 to 69.
Although individuals with the gene variant didn’t show a difference in their ability to identify the odor they were smelling until they reached 75 to 79 years, once this ability started to diminish, it declined more rapidly than those not carrying the gene.
Interestingly, thinking and memory skills were similar among the two groups at the beginning of the study. However, as anticipated, those carrying the gene variant experienced a more rapid decline in their cognitive abilities over time.
“Identifying the mechanisms underlying these relationships will help us understand the role of smell in neurodegeneration,” said GoodSmith.
Limitations and Future Directions
The study did not include individuals with severe dementia, representing a potential limitation. Further research will be crucial to confirm these findings and understand the level of smell loss that might predict future cognitive risks.
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The study was published in Neurology.
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