Masoumeh Falah - ENT and Head & neck Research Center and Department, Iran University of Medical Sciences
Mohammad Farhadi - ENT and Head & neck Research Center and Department, Iran University of Medical Sciences
Seyed Kamran Kamrava - ENT and Head & neck Research Center and Department, Iran University of Medical Sciences
Maryam Balali - ENT and Head & neck Research Center and Department, Iran University of Medical Sciences

Presbycusis or Age-related hearing impairment (ARHI) is the most frequent sensory disorder in the elderly. It affects more than half of all persons by age seventy-five years. ARHI has profound economic and social health impacts moreover, the increasing elderly population makes ARHI as an important issue for future generations. Presbycusis is an irreversible symmetrical progressive loss of hearing sensitivity during the lifespan. It has an insidious onset without clinical manifestation so detected by the routine test after losing or damaging to inner ear cells and neurons. Presbycusis counted as an untreatable impairment, since these inner ear structures lose the ability of regeneration.Mitochondria by producing reactive oxygen species or inducing apoptotic genes is one of most prominent organelles in presbycusis progression. The present study focused on mitochondrial function in order to find the per-diagnostic biomarker for this common impairment. For obtaining this goal the relative mitochondrial DNA (mtDNA) copy number and control region variation compared between presbycusis and healthy subjects. All participants selected by an otolaryngologist after ENT examination, audiology investigation. The proportion of mtDNA to nuclear DNA calculated by quantitative real-time PCR, and variations in the mtDNA control region were investigated by PCR and sequencing. Results indicated that mtDNA copy number were decreased in presbycusis subjects compared with healthy subjects. The frequencies of the variants, 16223 C> T, 16311 T> C, 16249 T> C, and 15954 A> C, were significantly different between presbycusis and control subjects too.The statistically significant difference copy number and control region variation of mtDNA in ARHI patients and controls is in agreement with previous experimental evidence and supports the role of mitochondria in the intracellular mechanism underlying ARHI development. Moreover, this study showed that mitochondrial investigation will enable to establish biomarkers helping to identify individuals at risk for developing presbycusis and to develop screening approaches for pre-diagnosis.

Presbycusis, Age-related hearing impairment (ARHI), Pre-diagnostic, Biomarker