PMD cohort age group at SNHL onset. SNHL age of onset was determined based on first EMR mention of hearing concerns occurring in individuals subsequently diagnosed by formal audiologic evaluation. Age groupings were based on standard development trajectory categorization, including prelingual (before development of spoken language, <2 years), preschool (2-5 years), school-age child (6-12 years), adolescent (13-19 years), young adult (20-40 years), and middle age to elderly adult (>40 years). PMD, Primary mitochondrial disease; SNHL, Sensorineural hearing loss; SLSMD, Single large-scale mtDNA deletions; EMR, Electronic medical records. *** p-value <0.001