Description
Alzheimer's disease (AD) is a common form of dementia that is marked by the presence of A_-plaques, neurofibrillary tangles and cognitive decline. The biggest risk factor for AD is age, as 81% of individuals with AD are 75 years old or older. There is increasing evidence that AD pathology may begin decades before clinical symptoms appear, beginning in the entorhinal cortex. Studies have shown cognitively healthy older adults perform significantly worse on tasks of odor recognition memory, recall and identification than young adults, with this decline more pronounced in those over the age of 65. Interestingly, the latency of brain response to odor identification in older adults is related to one's body mass index (BMI) and waist circumference, with longer response time in those with higher BMIs and larger waist circumferences. Few studies have investigated the links between odor discrimination, AD and aging, and none have investigated the influence of BMI on odor discrimination. This study examined olfactory event-related potentials (OERPs) in an odor quality discrimination task. Participants were separated into two age groups: young (18-28 years) and older (65+). Odor discrimination were administered a task in which participants were presented with pairs of odors and asked to indicate whether the odors in a pair were the same or different. Participants were also administered an analogous visual task using pairs of colors. Latencies and amplitudes of the OERPs were examined for the N1, P2, N2 and P3 components at the Fz, Cz and Pz electrode sites. A repeated-measures ANOVA with BMI and waist circumference as covariates revealed a significant influence of BMI status on N2 & P3 amplitude when odor pairs were classified as "different." There were significant effects of waist circumference and BMI on N1 latency. The findings support research suggesting negative effects of a high BMI and waist circumference on ERP recordings during olfactory mediated tasks. As obesity is considered a risk factor for developing AD, deficits in olfactory function as shown by OERPs in conjunction with high BMI could serve as a biomarker for changes in the brain associated with AD.
