Supplementary Material for: A Nationwide, Population-based Study of Intelligence and Hearing Loss Among 3,104,851 Adolescents

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 and sensorineural HL, stratified by severity. This study examined the connection between HL and GI in late adolescence.

Methods: Cross-sectional study on mandatory pre-military recruitment data recorded during 1967-2019 of patients aged 17-19. We compared GI between sensorineural HL, conductive HL, 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 hearing loss (HL). We categorized general intelligence (GI) into three levels for analysis: low (lowest category), medium, and high (reference category). Adjusted odds ratios (ORs) revealed that sensorineural HL (SNHL) was associated with lower GI levels, with ORs ranging from 1.3 [95% CI 1.4–1.2] for the lowest GI category to 1.1 [95% CI 1.15–0.04] for the medium category. Conductive HL (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 odds ratios 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. Sensorineural HL, but not conductive HL, 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.

目的：流行病学研究已证实青少年时期的一般智力（GI）与听力损失（HL）之间存在关联。然而，尚无大规模研究评估青春期晚期GI与传导性听力损失（conductive HL）及感音神经性听力损失（sensorineural HL）的关系，并按严重程度分层分析。本研究旨在探讨青春期晚期HL与GI之间的关联。

方法：采用横断面研究设计，分析1967-2019年间17-19岁青少年的强制性入伍前招募数据。比较感音神经性HL、传导性HL与听力正常人群的GI水平；此外，在调整年龄、性别、教育程度及社会经济地位后，通过逻辑回归分析HL与GI之间的关联。

结果：共纳入3,104,851名青少年受试者，其中20,075人（0.6%）存在听力损失（HL）。研究将一般智力（GI）分为低、中、高三个水平（高GI为参照组）。调整后的比值比（OR）显示，感音神经性HL（SNHL）与较低GI水平相关：低GI组OR为1.3[95%置信区间（CI）1.4–1.2]，中GI组OR为1.1[95%CI 1.15–0.04]。传导性HL（CHL）亦与GI存在显著关联：低GI组OR为1.8[95%CI 1.9–1.6]，中GI组OR为1.1[95%CI1.2–0.9]。进一步分析显示，SNHL严重程度与GI最低四分位（Q1）的发生风险呈统计学显著的剂量反应关系：随着严重程度增加，OR值从1.2[95%CI1.1–1.3]升至1.3[95%CI1.1–1.5]，表明SNHL越严重，认知表现越差。相比之下，CHL严重程度与GI结局无一致性关联，各严重程度的OR值均为1.6[95%CI1.2–2.3]。

结论：本研究证实青春期晚期HL与GI之间存在密切关联。感音神经性HL（而非传导性HL）的严重程度与GI下降呈正相关。研究结果强调了针对HL病因及严重程度开展早期精准治疗的重要性。