It’s Possible that People with the Alzheimer’s Risk Gene will Lose Their Ability to Detect Odors Earlier

According to a study that was published in the online issue of Neurology®, the medical journal of the American Academy of Neurology, on July 26, 2023, people who carry the gene variant that is associated with the strongest risk for Alzheimer’s disease may lose their ability to detect odors earlier than people who do not carry the gene variant. This may be an early sign of future memory and thinking problems. APOE e4 is the name of the gene variant that is linked to this increased risk of Alzheimer’s disease.

Over 865 individuals were tested on their sense of smell during an at-home survey as part of the study. These participants were asked to describe the odor they were smelling as well as whether they were able to detect any odor at all. At intervals of five years, tests were given. Additionally, brainpower and memory were tested twice, each five years apart. Researchers were able to learn from DNA samples who was carrying the gene that was linked to an increased risk of Alzheimer’s disease.

Depending on how many different concentrations of odors a person could smell, their scores on the test to see if they could smell smells ranged from zero to six.

At a single timepoint, people with the gene variant had a 37% lower likelihood of having good odor detection than people without the gene. Age, sex, and educational level were all taken into account by researchers as additional variables that could influence the outcomes. The quality transporters began encountering decreased smell detection at age 65 to 69. At that age, the gene carriers could identify a normal of around 3.2 of the smells, contrasted with around 3.9 smells for individuals who didn’t carry the gene.

Individuals carrying the gene variant didn’t show a difference in their ability to recognize what odor they were smelling until they arrived at age 75 to 79. The gene-carrying individuals lost their ability to identify odors more quickly than those who did not carry the gene.

Thinking and memory abilities were comparable among the two gatherings toward the beginning of the study. However, as was to be expected, those with the gene variant saw their thinking abilities decline more rapidly over time than those without the gene.

“Identifying the mechanisms underlying these relationships will help us understand the role of smell in neurodegeneration,” GoodSmith said.

The lack of inclusion of individuals with severe dementia is a limitation of the study.

The National Institutes of Health, National Institute on Aging, and National Institute of Diabetes and Digestive and Kidney Diseases all provided financial support for the study.