The Effect of Real Ear Target Deviations on SSQ and Speech Intelligibility in a Clinical Population

The quality of hearing-aid (HA) fitting is typically evaluated using speech intelligibility tests and/or Real-Ear Measurements (REMs). Although it is assumed that a better fit improves daily outcomes, supporting evidence is inconclusive. This study examined whether deviations from National Acoustic Laboratories Non-Linear (NAL-NL2) real-ear targets (real-ear-to-target difference, RTD) predicted changes in Speech, Spatial, and Qualities of Hearing Scale (SSQ) scores, and whether they related to aided speech recognition in quiet. The effects of hearing loss and patient characteristics were also considered. Data from 298 adults (mean age 65 years) fitted with new or replacement HAs (66%) were analyzed. Baseline measures included unaided speech recognition in quiet and a 17-item SSQ; follow-up measures included aided speech recognition in quiet, RTDs, and the SSQ. Principal Components Analysis summarized RTDs into overall gain (RTD₁) and high-frequency gain (RTD₂). The effects of treatment, RTD, pure-tone average (PTA), audiogram slope, asymmetry, age, gender, and HA experience on SSQ scores were investigated with mixed-effects models. Hearing-aid use improved both SSQ score (by 1.4 points) and speech in quiet. The RTD₁ predicted neither SSQ nor speech scores. Underamplification above 2 kHz (RTD₂) did not influence speech scores significantly, but reduced SSQ improvement. Higher PTA and steeper slopes were associated with lower aided speech scores, while higher PTA and age reduced SSQ improvement. Hearing-aid experience showed modest SSQ-domain effects. About half of SSQ variance reflected between-subject differences. HAs provide substantial benefit, despite moderate NAL-NL2 mismatches. Accurate 4-8 kHz fittings maximize outcomes by the SSQ, supporting REM-guided fitting practices.