The decrease in the number of mtDNA copies can be considered a manifestation of decremental copy regulation. Researchers link changes in mtDNA-CN levels in patients with neurodegenerative diseases to mitochondrial dysfunction, cognitive decline, disease progression, and ultimately, therapeutic intervention. Changes in mitochondrial function and content are one of the potential determinants of neurodegenerative diseases. Changes in mitochondrial DNA copy number (mtDNA-CN) levels in biological fluids occur during both the early stages of the disease and its progression . Polymorphic mtDNA variants, such as point mutations, deletions, and copy number variations, raise the risk of cancer, neurodegenerative diseases (like Parkinson's disease and Alzheimer's disease), and rare neurological diseases that can happen to anyone or are passed down through families .