Hearing aids may reduce cognitive decline in adults: Lancet study

Hearing aids may protect against cognitive decline in older adults at greater risk of dementia, according to a study published on Tuesday in The Lancet journal.Hearing aids may reduce cognitive decline in adults: Lancet study

The findings are based on the first randomised controlled trial (RCT) of its kind involving nearly 1,000 older adults from multiple locations across the US.

"These results provide compelling evidence that treating hearing loss is a powerful tool to protect cognitive function in later life, and possibly, over the long term, delay a dementia diagnosis," said Professor Frank Lin of Johns Hopkins University School of Medicine and Bloomberg School of Public Health, US.

"But any cognitive benefits of treating age-related hearing loss are likely to vary depending on an individuals' risk of cognitive decline," said Lin.

Age-related hearing loss is extremely common, affecting two-thirds of adults aged over 60 globally, the researchers said.

However, less than 1 in 10 individuals with hearing loss in low- and middle-income countries, and fewer than 3 in 10 in high-income countries, currently use hearing aids, they said.

Untreated hearing loss is associated with greater cognitive decline and was estimated by the 2020 Lancet Commission on Dementia to contribute to around 8 per cent of dementia cases worldwide -- equivalent to 8 lakh of the nearly 10 million new cases of dementia diagnosed every year.

Previous observational research suggests that treating hearing loss may protect against cognitive decline and dementia, the researchers said.

However, these studies may be biased because individuals who have the means and choose to get their hearing loss treated may be healthier and at lower risk of cognitive decline than those who don't, they said.

As a result, the effectiveness of hearing aid use on reducing cognitive decline in cognitively-healthy older adults with hearing loss remained unclear.

To provide more robust evidence, the latest study included 977 adults aged 7084 years with untreated hearing loss who were free from substantial cognitive impairment in four communities across the US.

Participants were recruited from two populations at each site: older adults participating in a longstanding observational study of cardiovascular health (Atherosclerosis Risk in Communities [ARIC] study), and new volunteers from the same communities who were generally healthier than participants from ARIC.

Participants were randomised to either a hearing intervention (audiological counselling and hearing aids) or the control intervention involving more generalised counselling on healthy ageing and were followed-up twice a year over 3 years.

The primary analysis of the results, combining both the ARIC and volunteer cohorts, found that the hearing intervention did not reduce cognitive decline over timewith no significant difference in cognitive change between those receiving the hearing intervention and the health education control over 3 years.

However, in the ARIC cohort, 3-year cognitive change was 48 per cent lower in the hearing intervention group than the control group.

In contrast, in the healthy volunteer cohort (who had fewer risk factors for cognitive decline and a much slower rate of cognitive decline), 3-year cognitive change did not differ significantly between the hearing intervention and control groups.

No significant adverse events were reported in either group.

"Although our primary analysis of the combined ARIC and health volunteer cohorts did not find a difference in cognitive decline for those using hearing aids, when we did sensitivity analyses to test its robustness there was clear evidence indicating a significant benefit for older adults in the ARIC cohort who had more risk factors for cognitive decline," Lin said.

"Despite similar levels of hearing at the start of the study, it's likely that volunteers in the healthier cohort experienced slower rates of cognitive change than ARIC participants because they tended to be younger, had fewer risk factors for cognitive decline, and had better initial cognitive scores," he added.