The "incidence" of aphasia refers to the number of new cases identified in a specified time period. It is estimated that there are 80,000 new cases of aphasia per year in the United States (National Stroke Association, 2008).

"Prevalence" of aphasia refers to the number of people who are living with aphasia in a given time period. The National Institute of Neurological Disorders and Stroke (NINDS) estimates that approximately 1 million people, or 1 in 250 in the United States today, suffer from aphasia (NINDS, n.d.).

Based on population growth estimates (Lingraphica, n.d.), the incidence of aphasia in the United States is expected to rise to 180,000 cases per year by 2020, with the prevalence then being 2 million persons living with aphasia.

Fifteen percent of individuals under the age of 65 experience aphasia; this percentage increases to 43% for individuals 85 years of age and older (Engelter et al., 2006).

No significant differences have been found in the incidence of aphasia in men and women. However, some data suggest differences may exist by type and severity of aphasia. For example, Wernicke's and global aphasia occur more commonly in women and Broca's aphasia occurs more commonly in men (Hier, Yoon, Mohr, & Price, 1994; National Aphasia Association, 2011).