Objectives: To evaluate the effect of hearing devices for adults with mild-to-severe hearing losses. Specifically, we assessed the magnitude of change across outcome domains, identified measurement tools used, and reported adverse effects associated with device use.

Design: We conducted a systematic review and meta-analysis following PRISMA guidelines. Searches were performed in PubMed, CINAHL, and Embase. Included studies were randomized controlled trials (RCTs) involving adults (≥18 years) with mild-to-severe hearing loss, comparing any air conduction hearing device to passive or active controls. Effect sizes were calculated as Hedges’ g, and random-effects models estimated pooled effects.

Results: Thirty-three randomized controlled trials (N = 4,471 participants) met the inclusion criteria, although pooled estimates could be derived from only a subset of trials due to limited reporting. Hearing aids demonstrated moderate-to-large benefits on hearing-related self-report outcomes compared with no-intervention or waitlist controls; however, pooled meta-analytic estimates could not be generated for this comparison because of insufficient data across trials. Compared with placebo, hearing aids yielded a small pooled effect (g ≈ 0.37), driven largely by trials including participants with comorbid Alzheimer’s disease. Personal sound amplification products (PSAPs) showed a pooled medium effect compared with no intervention (g ≈ 0.42), with benefits primarily observed for hearing-specific self-report outcomes and selected behavioral measures. In head-to-head comparisons, hearing aids showed a large pooled advantage over other hearing devices, including smartphone hearing aid applications (SHAA) and extended-wear hearing aids (EWHA) (g ≈ 0.88), based on data from two trials. Across the included studies, most outcomes were self-reported (≈81%), behavioral (≈45%), with very limited assessment of cognitive or neurophysiological domains. Nine studies reported adverse events, with only one device-related incident. Heterogeneity was high (I²>80%), but no publication bias was detected.

Conclusion: Hearing aids provide substantial benefit for hearing-related self-reported outcomes in comparison to PSAPs, smartphone hearing aid applications, extended-wear hearing aids, and placebo. However, high heterogeneity prevents reliable conclusions based on pooled estimates. There also remains limited evidence on cognitive, neurophysiological, and long-term behavioral outcomes, underscoring the need for more rigorous, domain-diverse RCTs in this field.