[The first hearing aid increases mental capacity. Open controlled clinical trial as a pilot study].
According to the scientific literature, a hearing impairment which is acquired late reduces mental efficiency. To determine by empirical examination whether hearing aids increase mental efficiency. PERSONS AND METHODS: An open controlled application study was carried out on the capacity of working memory in 15 first users of hearing aids. The working memory's capacity in the 15 users (age: 72+/-12 years; six females; crystallized IQ: 100+/-13; test-retest period: 74+/-35 days) increased 13+/-19% (IQ-increment 3.4+/-6.3 points), while the capacity of the 15 controls (age: 71+/-11 years; seven females; crystallized IQ: 103+/-12; test-retest period: 58+/-21 days) remained unchanged: 0+/-12% (IQ-change: -0.3+/-5.1 points). The difference between the samples is significant (p=0.012 one-tailed). The visually and auditively administered subtests yielded equal changes. According to self-reports, the daily wearing time was 6.7+/-3.5 h. Daily wearing times of the hearing aids (self-reports) of between 4-8 h showed the multiple IQ-gain compared to lesser or longer times. The audiometric gain in hearing without noise on the right (rho=0.58; significant), left (0.48; not significant), and on both sides (0.68; significant) correlated with IQ-gain. Under a more favourable usage a still more striking benefit is to be expected in mental efficiency.