A recent study suggests that changes in a person's sense of smell may be an early indicator of cognitive decline in individuals who are genetically predisposed to develop Alzheimer's disease. The research, conducted by a team at the University of Chicago, focused on the connection between the sense of smell and cognition, as memory problems are a key feature of Alzheimer's.
The study found that a specific gene variant called APOE4, which is associated with an increased risk of Alzheimer's, is highly expressed in parts of the sensory system related to smell. People who carry this variant are more likely to develop Alzheimer's compared to those without it.
To investigate the link between APOE4 and sense of smell, the researchers analyzed data from the US National Social Life, Health, and Aging Project. Participants aged 62 to 85 were genetically screened for the APOE4 variant and tested on their cognition and sense of smell. The tests were repeated in 2015.
The results showed that individuals with the APOE4 variant experienced a decline in their ability to differentiate between different concentrations of the same odor and to identify different odors. This decline in odor sensitivity was observed between the ages of 65 and 69. Additionally, the carriers of the variant exhibited a more rapid decline in thinking and memory skills compared to non-carriers.
The researchers suggest that testing a person's sense of smell could be a useful tool in predicting the development of Alzheimer's symptoms within the next five years, especially for individuals who are already genetically susceptible to the disease. However, it is important to note that this study did not track who went on to develop Alzheimer's or any signs of it in the brain.
The team believes that smell testing should be as widely available for older individuals as vision and hearing tests. Early detection of brain health abnormalities is crucial for implementing therapies as soon as possible in the disease course, as treatment earlier in the disease generally has a larger impact.
Further research is needed to validate these findings and determine the potential of odor sensitivity testing in improving Alzheimer's diagnoses and enabling early treatment.