For 1971, 1977, and 1978, chronic hearing problem records were defined as those condition records with any of the following codes in the variable DIAGR1 in the original NHIS public use files.

• "X07" ("Hearing loss ... involving both ears [other than total deafness in both ears]")

• "X08" ("All hearing impairments involving only one ear")

• "X09" ("Hearing loss, complete or partial, for which it is impossible to determine whether one or both ears are involved")

These condition code values come from NCHS's Diagnostic Recode #1: Diseases, Injuries, and Impairments, not from the International Classification of Diseases (ICD) codes. Additionally, to be considered "chronic," hearing problem records must have a code of "1" ("Chronic") in the variable CACODE in the original NHIS public use files.

For 1979-1981, chronic hearing problem records were defined as those condition records with any of the following codes in the variable DIAGR1 in the original NHIS public use files:

• "X06" (Hearing impairment involving both ears [other than total deafness in both ears]. Any bilateral hearing impairment which cannot be coded to X05 [X05 = Deafness, both ears])

• "X07" ("Deafness or hearing impairment of any degree involving only one ear")

• "X08" ("Deafness, not otherwise specified. Unknown whether one or both ears are involved.")

• "X09" ("Impaired hearing, not otherwise specified. Unknown whether one or both ears are involved.")

These condition code values come from NCHS's Diagnostic Recode #1: Diseases, Injuries, and Impairments, not from the International Classification of Diseases (ICD) codes. As with earlier years, to be considered "chronic," hearing problem records must have a code of "1" ("Chronic") in the variable CACODE in the original NHIS public use files.

For 1982-1996, chronic hearing problem records were defined as those condition records with either of the following codes in the variable C1CONDRB in the original NHIS public use files:

• "240" ("Otitis media and mastoiditis")

• "249" ("Residual diseases of the ear and mastoid process" [i.e., conditions other than deafness, otitis media, and mastoiditis])

These condition code values come from NCHS's Diagnostic Recode B: Diseases, Injuries, and Impairments, not from the International Classification of Diseases (ICD) codes. As with earlier years, to be considered "chronic," hearing problem records must have a code of "1" ("Chronic") in the variable CACODE in the original NHIS public use files.