Cochlear implants can improve speech and quality of life in adults with severe hearing loss, according to a new analysis of past studies - and two implants seem to work better than one.
The implants, which are surgically placed into and behind the ear, transmit sound directly to the auditory nerve.
"Cochlear implantation is just a hugely beneficial procedure for the people who need it. It's almost like magic," said Dr Pamela Roehm, an otolaryngologist from the NYU Langone Medical Center who wasn't involved in the new study.
"Their hearing isn't completely normal, but for speech (and) understanding, it's so good," she said.
According to the National Institutes of Health, about 17% of American adults have some degree of hearing loss, and the chance of becoming hard of hearing increases with age. Only those with severe hearing loss or deafness, for whom hearing aids haven't worked, are considered for cochlear implants.
The new analysis included 42 studies that compared hearing, speech and quality of life in eligible adults before and after they received a cochlear implant, or compared having one versus two functioning implants.
Those studies used a range of tests over different time periods to measure the effects of implantation, so it was difficult to compare them directly, researchers led by James Gaylor from Tufts Medical Center in Boston. However, almost all trials looking at the effect of a single cochlear implant showed that people's speech and quality of life improved after implantation.
Among studies comparing one versus two implants, the majority also found participants were better at communicating and localising sound when they had a cochlear implant in each ear. It wasn't clear how much of an effect a second implant had on their quality of life, however.
Cochlear implants cost about $50 000 each, which is covered by most insurance providers. Through 2010, approximately 43 000 adults and 28 000 children had received an implant in the US. Possible complications of implantation include infection or damage to the device. But Roehm said all things considered, it's a pretty minor procedure.
"It's surgery - you have to have general anaesthesia - but as surgeries go, it's not very risky (and) you don't lose a lot of blood," she said. She and her colleagues have implanted people over 90 years old, Roehm said, with good results. The implants aren't perfect - they may help people communicate better in person and on the phone, but they don't always allow them to listen to music, for example, she noted.
The new findings don't mean that deafness has a detrimental effect on quality of life, said Gaylor. He added that for some in the deaf community, cochlear implants are still controversial.
"Our hope is that this paper will allow providers, payers, and most importantly patients to ... make more informed decisions about cochlear implantation," Gaylor wrote.