Early intervention influences 9-year speech, language, cognitive, and quality-of-life outcomes in deaf or hard-of-hearing children

OBJECTIVES: Early identification of congenital deafness enables early intervention, but evidence on the influence of age at fitting of hearing aids (HAs) or cochlear implants (CIs) on outcomes in school-aged children who are deaf or hard of hearing (DHH) is limited. This study (1) described developmental outcomes and health-related quality of life in DHH children; and (2) examined the relationships among demographic factors, including age at fitting of HAs or CIs, and outcomes.

DESIGN: This prospective cohort study included participants in a population-based study who were followed up at 9 years of age. Children who are DHH and who first received hearing habilitation services before 3 years of age from the government-funded national hearing service provider in the states of New South Wales, Victoria, and Southern Queensland in Australia were invited to enroll in the study. At 9 years of age, enrolled children were assessed using standardized measures of language, cognitive abilities, and speech perception. The children also completed questionnaire ratings on their quality of life. Parents provided demographic information about their child, family, and education; and completed ratings on their child's quality of life. Audiological data were retrieved from the client database of the hearing service provider and records held at CI centers. Descriptive statistics were used to report quantitative outcomes. The relationships among demographic characteristics, including age at fitting of HAs or CIs, and children's outcomes were examined using structural equation modeling.

RESULTS: A total of 367 children, 178 (48.5%) girls, completed assessments at age 9.4 (SD = 0.3) years. On average, performance was within 1 SD of the normative mean for language, cognitive functioning, and health-related quality of life; but much below norms for speech perception. The modeling result is consistent with verbal short-term memory having a mediating effect on multiple outcomes. Better verbal short-term memory is significantly associated with no additional disabilities, earlier age at CI activation, use of an oral communication mode in early intervention, and higher maternal education. In turn, verbal short-term memory directly and positively affects speech perception, language, and health-related quality of life. Maternal education directly and positively affects language outcomes, and indirectly via its effects on nonverbal I.Q. and verbal short-term memory. Better language is directly associated with a better quality of life.

CONCLUSIONS: This study found evidence consistent with early hearing intervention having a positive effect on speech perception and language via its effect on verbal short-term memory. Children who had better language also had better quality of life. The importance of early hearing for cognitive development lends support to early detection and early hearing intervention, including streamlining pathways for early CI activation. Strategies for intervention in language and communication development may benefit from tailoring programs to meet the needs of individuals with different memory profiles for optimizing outcomes.