AMA Manual of Style - Stacy L. Christiansen, Cheryl Iverson 2020

Age and Sex Referents
Correct and Preferred Usage

Use specific terms to refer to a person’s age.

Neonates or newborns are persons from birth to 1 month of age.

Infants are children aged 1 month to 1 year (12 months).

Children are persons aged 1 to 12 years. Sometimes, children may be used more broadly to encompass persons from birth to 12 years of age. They may also be referred to as boys or girls.

Adolescents are persons aged 13 through 17 years. They may also be referred to as teenagers or as adolescent boys or adolescent girls, depending on context.

Adults are persons 18 years or older and should be referred to as men or women. Persons 18 to 24 years of age may also be referred to as young adults.

Note: If the age of an individual patient is given, it may be expressed as a mixed fraction (eg, 6½ years) or as “6 years 6 months.” However, when age is presented as a mean, use the decimal form: 6.5 years (see 19.4.1, Study Design and Statistics, Significant Digits and Rounding Numbers, Significant Digits).

Whenever possible, a patient should be referred to as a man, woman, boy, girl, or infant. Occasionally, however, a study group may comprise children and adults of both sexes. Then, the use of male and female as nouns is appropriate. Male and female are also appropriate adjectives.

See 11.12.4, Inclusive Language, Age.