Grant: Doctoral Award - Frederick Banting and Charles Best Canada Graduate Scholarships

Alzheimer's disease (AD) is the most common cause of dementia; it affects roughly 747,000 adults in Canada and its prevalence will triple over the next 40 years. A single episode of a lifetime history of major depression (LMD) is linked to more than twofold increase in risk of AD. Neurofibrillary tangles (NFTs) and beta-amyloid are two most prominent biomarkers in the brains of patients with AD. Levels of NFTs and beta-amyloid can be measured using an imaging technique called Positron Emission Tomography (PET) using radioactive dyes that bind to NFTs and beta-amyloid. Mild cognitive impairment (MCI) is a transitional risk state between normal aging and AD. Our previous study shows that level of beta-amyloid is increased in patients with MCI with an LMD (MCI+LMD) specifically in the frontal regions in comparison to patients with MCI without an LMD (MCI-LMD). This suggests that depression increases the level of beta-amyloid in brain regions associated with depression. So far, NFT regional deposition has not been explored in MCI+LMD patients. The primary aim of this study is to compare the total levels, and the different regions of NFT depositions between MCI+LMD and MCI-LMD patients. We hypothesize that MCI+LMD patients will show higher levels of NFTs than MCI-LMD patients in brain regions associated with depression, including frontal, cingulate and hippocampal regions. We will scan patients with a novel radioactive dye ([18F]-T807) to measure brain regional levels of NFTs. Over 3 years, we will scan 14 MCI+LMD and 14 MCI-LMD patients. Our findings will provide a new insight to the understanding of the complex relationship between major depression and AD. Current literature suggests that more than 10% of AD cases worldwide is attributable to a major depression. Our findings can be translated to identify a high-risk population of developing AD, thus assist with the implementation of prevention strategies of AD, leading to novel therapeutic approaches.