Cognition, Gut-Brain Biomarkers, and Nutrition among those with Alzheimer's and Parkinson's Disease

This cross-sectional study examines gut-brain relationships in neurodegenerative disease across three objectives. Prior work links moderate consumption of refined grains with intake of whole grains, fruits, and dairy to reduced odds of MCI, whereas diets high in fried foods, high-sodium condiments, and processed snacks increase the risk of MCI (Kim & Yun, 2018; Malek Rivan et al., 2022). Using self-reported food frequency data from 162 participants (MCI: n = 81; no MCI: n = 81), this study hypothesizes that overall dietary quality, not individual food items, differentiates MCI status. Preliminary findings from available food logs suggest reduced consumption across food groups in MCI-positive individuals, supporting this hypothesis, though memory recall limitations in this population warrant caution. Full results are pending analysis of ~60 additional diet logs. IGF-1 promotes neuronal plasticity, clears amyloid-beta, and regulates muscle mass and gait speed in older adults, while declining with age and stimulated by exercise (Doi et al., 2015; Watanabe et al., 2005). This study hypothesizes lower IGF-1 in MCI-positive versus MCI-negative individuals, with results from dried blood spot analyses forthcoming. Clarifying this relationship may inform early detection and intervention strategies for age-related cognitive decline. PD is the second most common neurodegenerative disorder, with up to 80% of dopaminergic neurons lost before symptom onset (Emamzadeh & Surguchov, 2018). Gut dysbiosis promotes neuroinflammation and α-syn misfolding, which propagate via the vagus nerve to the brain (Chen et al., 2025; Klann et al., 2022), and oligomeric α-syn concentrates in memory-critical regions, producing cognitive deficits (Adamowicz et al., 2016). Salivary α-syn oligomers are elevated in PD patients versus healthy controls, suggesting saliva as a minimally invasive diagnostic source (Vivacqua et al., 2016). Baseline saliva samples from an ongoing clinical trial (Albany, NY; North Shore, MA) will be analyzed and correlated with executive function, memory, and UPDRS scores, controlling for demographic covariates. This study hypothesizes that elevated oligomeric α-syn will be associated with greater cognitive impairment, potentially serving as a practical biomarker for monitoring disease progression.