Iranian Association for Intelligence and Talent Studies International Journal of Education and Cognitive Sciences 3041-8828 7 September 2026 2026 09 01 Higher Serum Dopamine Is Associated with Greater Hippocampal Volume and Better Cognitive Function Across the Alzheimer’s Disease Spectrum Higher Serum Dopamine Is Associated with Greater Hippocampal Volume and Better Cognitive Function Across the Alzheimer’s Disease Spectrum 1 15 EN Journal Article 2026 02 11 <p><strong>Purpose: </strong>This study aimed to examine diagnostic-stage differences in serum dopamine, bilateral hippocampal volume, and cognitive performance; tested pooled and diagnosis-specific associations of serum dopamine with hippocampal volume and cognition; evaluated serum dopamine-by-diagnosis interactions; and assessed whether bilateral hippocampal volume statistically mediated the association between serum dopamine and cognitive performance.</p> <p><strong>Methods and Materials: </strong>Baseline ADNI data from 428 participants were analyzed. Associations among serum dopamine, MRI-derived bilateral hippocampal volume, and ADAS-Cog13 performance were examined using adjusted pooled and diagnosis-specific regression models. Mediation analysis tested whether bilateral hippocampal volume mediated the association between serum dopamine and cognitive performance. False discovery rate (FDR) correction was applied.</p> <p><strong>Findings: </strong>Serum dopamine and bilateral hippocampal volume declined across diagnostic stages, whereas cognitive impairment increased. In the pooled cohort, higher serum dopamine was associated with larger bilateral hippocampal volume (standardized β = 0.18, FDR-adjusted q = .002) and better cognitive performance (β = −0.17, q = .006). These associations were strongest in participants with mild cognitive impairment (MCI), in whom higher dopamine was associated with both larger hippocampal volume (β = 0.21, q = .009) and better cognitive performance (β = −0.19, q = .012). Larger bilateral hippocampal volume was independently associated with better cognitive performance (β = −0.35, q &lt; .001). Bilateral hippocampal volume significantly mediated the association between serum dopamine and cognitive performance (indirect effect = −0.063), accounting for 37.1% of the total association.</p> <p><strong>Conclusion:</strong> Higher serum dopamine was associated with greater hippocampal volume and better cognitive performance, partly mediated by hippocampal structural integrity.</p> https://journalecs.com/index.php/ecs/article/download/426/455