There are no reliable data on the incidence and prevalence of AOS in adults. The collection of these data is hindered by challenges associated with the common co-occurrence of AOS with aphasia and dysarthria (Duffy, 2006; Duffy, Strand, & Josephs, 2014) and the difficulty distinguishing among those disorders—particularly in distinguishing between AOS characteristics and phonological errors that can occur in aphasia (McNeil, Pratt, & Fossett, 2004).
McNeil, Robin, and Schmidt (2009) suggest that isolated AOS (i.e., AOS in the absence of dysarthria or aphasia) is very uncommon. Duffy (2013) observed that AOS was documented as the primary, but not necessarily the only, communication disorder for 6.9% of all motor speech disorders in the Mayo Clinic Speech Pathology practice. This percentage would undoubtedly increase drastically if the data included cases in which AOS was a secondary communication disorder (e.g., less severe than aphasia or dysarthria; Duffy, 2013).