[SBU with its ear to the ground. Hearing aids benefit mainly those with moderate hearing loss].
OBJECTIVE
This review focused on answering the following questions: 1. At what level of hearing loss can hearing aids be of sufficient benefit to motivate testing and prescribing? 2. What is known about the value of the various technical features in modern hearing aids?


METHODS
English language literature was searched for the period 1990 through December 2002 using Medline. The scientific quality of the retrieved literature was assessed by two reviewers.


RESULTS
Hearing aids benefit mainly those with moderate to severe hearing loss. Hearing aids amplify sound but do not provide normal hearing. In regard to sound quality and benefits in daily life, non-linear technology is better than linear. There is no evidence that digital hearing aids are superior to modern analog hearing aids. No clinical trials have shown that two hearing aids are superior to one hearing aid.


CONCLUSIONS
The need for further scientific studies is substantial.
D003362:Cost-Benefit Analysis; D019317:Evidence-Based Medicine; D006310:Hearing Aids / Q000009:adverse effects / Q000191:economics; D034381:Hearing Loss / Q000534:rehabilitation*; D006801:Humans; D019986:Persons with Hearing Disabilities / Q000534:rehabilitation*