Systematic review of the clinical and cost effectiveness of digital hearing aids.

The aim of the present study was to systematically review the clinical and cost effectiveness of hearing aids which use digital signal processing relative to other forms of hearing aid technology, in particular analogue-based aids. A comprehensive search for randomized controlled trials, randomized crossover trials and economic studies was undertaken. Trial quality assessment and data extraction were undertaken by two independent reviewers. Eight trials comparing digital to non-digital devices were identified--one randomized controlled trial and seven randomized crossover trials. The majority of these studies were of small sample size and of poor methodological quality. In the majority of cases (nine out of 13), there was no evidence of a significant difference in either laboratory scores (nine out of 13 outcomes assessed) or user function/quality of life scores (six out of nine outcomes assessed) between digital and non-digital devices. In addition, there was no significant difference in patient preference for digital compared to control aids (relative risk 1.93; 95% CI 0.70-5.35) when pooled across studies. No cost-effectiveness studies directly comparing digital to non-digital devices were identified. In conclusion, the evidence identified by this review provides no significant evidence of the clinical benefit of digital devices compared to analogue-based aids. However, these results are difficult to generalize to current UK practice as the analogue aids and types of fitting in the trials are not those typically used in the NHS.