Objective: The age at cochlear implantation (CI) is crucial in language development for children with congenital severe to profound hearing loss. Language development may be possible at the same rate as normal hearing children after CI. However, language delay prior to CI may continue, highlighting the need for early CI. This study aims to identify the rate of language development and determine influencing factors.
Methods: Subjects who underwent CI between January 1999 to December 2014 in the Department of Otolaryngology, Ajou University Hospital were included. The subjects were divided into four groups based on age at CI: Group 1 (CI before 24 months), Group 2 (CI between 24–35 months), Group 3 (CI between 36–47), and Group 4 (CI after 47 months). The rate of language development was calculated as the ratio of age-equivalent language to chronological age.
Results: On average, subjects were followed up for 10.3 [SD, 4.0] years. The ratio of receptive vocabulary was 1.2 [0.3] (Group 1), 0.9 [0.3] (Group 2), 1.4 [0.9] (Group 3), and 0.9 [0.4] (Group 4). For expressive vocabulary, those were 1.1 [0.3], 0.8 [0.3], 1.1 [0.5], and 1.0 [1.5], respectively, in Groups 1 to 4. There were not statistical differences between groups (P=0.141 in receptive vocabulary and P=0.759 in expressive vocabulary). Patients who underwent surgery after 3 years of age showed varied progression. Successful language development was possible even if CI was performed after 4 years of age for patients whose language development was progressing through hearing aids before CI. In receptive vocabulary, preoperative language delay, not age at the first CI, was a factor that slowed development (OR 1.125 [1.003–1.225], P=0.007). If the vocabulary delay is less than 24 months before CI, the patient may reach the level of normal hearing children at about 7.5 years (90 months) of age.
Conclusions: The degree of preoperative language delay may be more important in language development than the age of surgery. If delay is less than 24 months, the catch-up of development may be possible before entering elementary school.

**Objective**: The age at cochlear implantation (CI) is crucial in language development for children with congenital severe to profound hearing loss. Language development may be possible at the same rate as normal hearing children after CI. However, language delay prior to CI may continue, highlighting the need for early CI. This study aims to identify the rate of language development and determine influencing factors.
**Methods**: Subjects who underwent CI between January 1999 to December 2014 in the Department of Otolaryngology, Ajou University Hospital were included. The subjects were divided into four groups based on age at CI: Group 1 (CI before 24 months), Group 2 (CI between 24–35 months), Group 3 (CI between 36–47), and Group 4 (CI after 47 months). The rate of language development was calculated as the ratio of age-equivalent language to chronological age.
**Results**: On average, subjects were followed up for 10.3 [SD, 4.0] years. The ratio of receptive vocabulary was 1.2 [0.3] (Group 1), 0.9 [0.3] (Group 2), 1.4 [0.9] (Group 3), and 0.9 [0.4] (Group 4). For expressive vocabulary, those were 1.1 [0.3], 0.8 [0.3], 1.1 [0.5], and 1.0 [1.5], respectively, in Groups 1 to 4. There were not statistical differences between groups (_P_=0.141 in receptive vocabulary and _P_=0.759 in expressive vocabulary). Patients who underwent surgery after 3 years of age showed varied progression. Successful language development was possible even if CI was performed after 4 years of age for patients whose language development was progressing through hearing aids before CI. In receptive vocabulary, preoperative language delay, not age at the first CI, was a factor that slowed development (OR 1.125 [1.003–1.225], _P_=0.007). If the vocabulary delay is less than 24 months before CI, the patient may reach the level of normal hearing children at about 7.5 years (90 months) of age.
**Conclusions**: The degree of preoperative language delay may be more important in language development than the age of surgery. If delay is less than 24 months, the catch-up of development may be possible before entering elementary school.

Language-delayed age (age-equivalent language) is more important than chronological age to predict long-term outcomes of cochlear implantation in congenital hearing loss: Longitudinal outcomes for 10-year

It is with great pleasure and enthusiasm, that on behalf of the Cochlear Implant centers of the Radboud UMC in Nijmegen and Erasmus MC Sophia Children’s Hospital in Rotterdam to invite you to attend the 16th European Symposium on Pediatric Cochlear Implantation to Rotterdam, the Netherlands in 2023.

Yours sincerely, on behalf of the CI Centers at Radboud UMC and Erasmus MC,