According to a study published in the July 26, 2023, online issue of Neurology®, the medical journal of the American Academy of Neurology, people who carry the gene variant associated with the highest risk for Alzheimer’s disease may lose their ability to detect odours earlier than people who do not carry the gene variant, which may be an early sign of upcoming memory and thinking problems. The APOE e4 gene variation is linked to this elevated risk of Alzheimer’s.
Over 865 people’s sense of smell were tested as part of the study’s at-home survey, both for their capacity to detect any odour at all and for their capacity to identify the specific odour they were smelling. Tests were administered every five years. The ability to think clearly and recall information was also evaluated twice, five years apart. Researchers learned who possessed the gene linked to a higher risk of Alzheimer’s disease from DNA samples.
Scores for the odour detection test varied from zero to six depending on how many of the various odour concentrations the participants were able to detect.
At a particular timepoint, individuals with the gene variant were 37% less likely to have good odour recognition than individuals without the gene. Age, sex, and educational level were taken into account along with other variables that might have an impact on the findings. Age 65 to 69 was the onset of diminished smell sensitivity in the gene carriers. At that age, those who carried the gene could detect an average of approximately 3.2 odours, compared to an average of around 3.9 smells for those who did not.
Until they were between the ages of 75 and 79, the individuals who carried the gene mutation did not exhibit a difference in their capacity to recognise the type of odour they were experiencing.
