Relative and attributable risks for moderate to profound bilateral sensorineural hearing impairment associated with lower birth weight in children 3 to 10 years old.

OBJECTIVE: To determine the prevalence, relative risks, and attributable fractions for congenital bilateral sensorineural hearing impairment in relation to lower birth weight among children born in the 1980s and living in the metropolitan Atlanta area from 1991 through 1993. METHODS: We used the population-based, active case ascertainment Metropolitan Atlanta Developmental Disabilities Surveillance Program that conducts surveillance in the five-county metropolitan Atlanta area. Hearing impairment was defined as a bilateral, pure-tone hearing loss at frequencies of 500, 1000, and 2000 Hz averaging 40 dBs or more, unaided, in the better ear. Case children, 3 to 10 years of age, with sensorineural loss of presumed congenital origin were included in these analyses (n = 172). Prevalence rates and relative risks were computed for various birth weight categories by hearing level, sex, race, the presence or absence of coexisting developmental disabilities, and gestational age. Attributable fractions were calculated for low birth weight and very low birth weight children by race. RESULTS: The overall prevalence rate of presumed congenital bilateral sensorineural hearing impairment was 5.3 cases per 10 000 3-year survivors. The prevalence was 4.1 per 10 000 among children weighing >/=4000 g, 3.7 per 10 000 among those weighing 3000 to 3999 g, 6.6 per 10 000 among those 2500 to 2999 g, 12.7 per 10 000 among those 1500 to 2499 g, and 51.0 per 10 000 among those <1500 g. There was virtually no difference in birth weight-specific rates of hearing impairment across three hearing levels. The presence of coexisting developmental disabilities was associated with a much stronger inverse trend with birth weight. Black children weighing <2500 g had much higher rates of hearing impairment than comparable white children. The overall percentage of moderate to profound congenital bilateral sensorineural hearing loss in the entire study population that was attributable to children weighing <2500 g or <1500 g was estimated to be 18.9% and 9.4%, respectively. Prematurity did not alter the magnitude of risk among children weighing <2500 g. CONCLUSIONS: The results presented here provide recent estimates of the rates, relative risks, and attributable fractions for congenital bilateral sensorineural hearing impairment by birth weight among children in the United States. The elevated relative risks among children weighing 2500 to 2999 g and 1500 to 2499 g may have implications for future newborn hearing screening criteria.

Prevalence and characteristics of children with serious hearing impairment in metropolitan Atlanta, 1991-1993.

OBJECTIVES: There is a paucity of data describing the epidemiology of serious hearing impairment among children in the United States. This report provides information on the prevalence of serious hearing impairment among children born in the 1980s and living in the metropolitan Atlanta area in 1991-1993 and on the characteristics of children with serious hearing impairment. METHODS: Data for this report are drawn from the Metropolitan Atlanta Developmental Disabilities Surveillance Program, an ongoing, active case-ascertainment system for mental retardation, cerebral palsy, hearing impairment, and vision impairment among children 3 to 10 years of age. Hearing impairment was defined as a bilateral, pure-tone hearing loss at frequencies of 500, 1000, and 2000 Hz averaging 40 decibels or more, unaided, in the better ear. Both severity and type of hearing loss were examined. Cross-sectional as well as birth cohort prevalence rates of serious hearing impairment were computed by sex and by race. The presence of mental retardation, cerebral palsy, vision impairment, or a seizure disorder was also assessed. An attempt was made to determine the probable etiology of a subset of the cases. RESULTS: The average, annual prevalence rate for moderate to profound hearing loss was 1.1 per 1000. The prevalence rate increased steadily with age. Ninety percent of all cases for which the type of loss was recorded were sensorineural. The highest rate was seen among black male children (1.4 per 1000). Thirty percent of case children had another neurodevelopmental condition, most frequently mental retardation. Black male children also experienced the highest rate of presumed congenital hearing impairment. The mean age at which children with presumed congenital hearing impairment first met the surveillance case definition was 2. 9 years. A probable etiology could only be found for 22% of cases born in the study area. CONCLUSIONS: The data presented here provide information on the descriptive epidemiology of serious hearing impairment among United States children. The reasons for the higher rates among black children, especially males, may be a fruitful direction for further research.