Quantifying What Better-Ear PTA4 Does Not Capture: High-Frequency and Asymmetric Classification Discordance in Two Independent Adult Population Samples from Germany and the United States.

Background/

Objectives

The four-frequency better-ear pure-tone average (PTA4; 0.5-4 kHz) is the dominant population definition of hearing impairment but underweights frequencies above 4 kHz and ignores interaural asymmetry. We quantified, in two independent adult samples, the proportion of PTA4-normal adults with elevated high-frequency or asymmetric profiles and whether this has a self-report correlate.

Methods

Cross-sectional secondary analysis of two public datasets: the German HÖRSTAT/Aalen sample (2008-2012; N = 3105) and pooled US NHANES (2011-March 2020; N = 10,575; adults ≥ 20 years). The primary outcome, PTA4-discordant high-frequency loss, was defined a priori as better-ear PTA4 ≤ 25 dB HL with a better-ear 6-8 kHz mean (PTA68) > 25 dB HL, reported as the conditional proportion among PTA4-normal adults. Secondary outcomes were interaural asymmetry ≥ 15 dB and self-rated hearing trouble (NHANES AUQ054 ≥ 3).

Results

Among PTA4-normal adults, 34.3% (95% CI 32.5-36.2) of the German sample and a survey-weighted 28.2% (25.9-30.5) of the NHANES sample had PTA68 > 25 dB HL. Prevalence rose with age (≈three-fold odds per decade; two-fold for male sex; all p < 0.001). Of those with PTA68 asymmetry ≥ 15 dB, 75-85% remained PTA4-normal, although the more stringent unilateral-like pattern was rare (1.5-1.7%). Self-reported trouble was elevated in PTA4-discordant mild (OR 2.56) and strong (OR 3.50) groups (OR 1.43 per 10 dB PTA68).

Conclusions

Although disagreement between the two classifications is arithmetically expected, since they cover different frequencies, its magnitude is substantial and reproducible: roughly a quarter to a third of PTA4-normal adults (28-34%) carry an elevated PTA68, with a graded self-report correlate consistent with early high-frequency presbyacusis, and the same age structure emerges in two samples measured with different equipment and procedures. Because the 25 dB HL criterion is not age-referenced, an increasing share of the discordance at older ages represents expected presbyacusis rather than pathology, so the older-age figures should be read as counts above a fixed public-health threshold. Reporting a high-frequency companion metric (PTA68 or PTA346) alongside PTA4 would make this information visible without displacing the existing system.