Until someone has had a certain disease, they probably don't have the vocabulary to describe it. Illiteracy is widespread in the United States. According to the National Adult Literacy Survey, up to 44 million Americans are functionally illiterate, and another 50 million have only marginal reading skills. In other words, roughly half of the adult U.S. population has difficulty reading or trouble calculating numbers. People over age 65 make up the majority of the population with reading problems, along with the approximately 10 million Latinos in this country who don't speak any English.
Low income is typically another predictor of illiteracy.
It can be difficult, however, to identify illiteracy, in part because it carries such a stigma. One study found that some patients find literacy problems more embarrassing than an incestuous relationship. They are unlikely to admit that they are illiterate. The good news is that residents are in a position to help illiterate patients with comprehension problems. The interactions between residents and patients may be brief, but they are intense.