A Nationwide, Population-Based Study of Intelligence and Hearing Loss among 3,104,670 Adolescents

Abstract

Purpose: Epidemiological studies have demonstrated a relationship between general intelligence (GI) in youth and hearing loss (HL). However, no large-scale study assessed the relations of GI in late adolescence with conductive HL (CHL) and sensorineural HL (SNHL), stratified by severity. This study examined the connection between HL and GI in late adolescence. Methods: Cross-sectional study on mandatory premilitary recruitment data recorded during 1967–2019 of patients aged 17–19. We compared GI between SNHL, CHL, and those with normal hearing. In addition, we used logistic regression to measure the associations between HL and GI after adjuring for age, sex, education, and socioeconomic status. Results: Among 3,104,851 adolescents assessed, 20,075 (0.6%) exhibited HL. We categorized GI into three levels for analysis: low (lowest category), medium, and high (reference category). Adjusted odds ratios (ORs) revealed that SNHL was associated with lower GI levels, with ORs ranging from 1.3 (95% confidence interval [CI] 1.4–1.2) for the lowest GI category to 1.1 (95% CI 1.15–0.04) for the medium category. CHL (CHL) also demonstrated significant associations, with ORs from 1.8 (95% CI 1.9–1.6) for the lowest GI level to 1.1 (95% CI 1.2–0.9) for medium. Further analysis revealed a statistically significant, severity-dependent relationship between SNHL and the odds of being in the lowest GI quartile (Q1). Specifically, the ORs for SNHL ranged from 1.2 (95% CI 1.1–1.3) to 1.3 (95% CI 1.1–1.5) as severity increased, indicating a strong link between greater SNHL severity and reduced cognitive performance. In contrast, CHL did not show a consistent correlation between its severity and GI outcomes, with an OR of 1.6 (95% CI 1.2–2.3) across severity levels. Conclusion: We report a strong relationship between HL and GI in late adolescence. SNHL, but not CHL, demonstrated a severity-based decline in GI. The results highlight the value of early, specifically targeted therapies for HL that consider its etiology and degree.