A landmark study published in The Lancet has shed light on the relationship between hearing loss and cognitive decline in older adults.
While hearing aids and audiological support services did not have a significant impact on cognitive decline in a general population of older adults over a 3-year period, treating hearing loss proved beneficial for older adults at a higher risk of dementia.
“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,” says Professor Frank Lin of Johns Hopkins University School of Medicine and Bloomberg School of Public Health. “But any cognitive benefits of treating age-related hearing loss are likely to vary depending on an individuals’ risk of cognitive decline.”
This first-of-its-kind randomized controlled trial (RCT) involved nearly 1,000 older adults from multiple locations across the USA. The participants, aged between 70 and 84 years, had untreated hearing loss but were free from substantial cognitive impairment at the start of the study.
They were divided into two groups: one received a hearing intervention, which included audiological counseling and hearing aids, while the other group received general counseling on healthy aging.
The study aimed to examine the 3-year change in global cognition scores, covering various tests of executive function, language, and memory, completed at the beginning of the study and then annually. The researchers found that, on average, the hearing intervention did not significantly reduce cognitive decline in the combined group of participants.
However, further analysis revealed fascinating results. The hearing intervention had a remarkable effect on older adults at greater risk of cognitive decline, such as those from the ARIC cohort (participants in a long-standing observational study of cardiovascular health) who tended to be older, female, and had more risk factors for cognitive decline. In this high-risk cohort, the cognitive decline was 48% lower in the hearing intervention group than in the control group.
On the other hand, the healthy volunteer cohort, who had fewer risk factors for cognitive decline and a much slower rate of cognitive decline, did not show a significant difference in cognitive change between the hearing intervention and control groups.
“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,” says Professor Lin.
He continues, “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. This much slower rate of cognitive decline may have limited any effect of hearing aids in further reducing this decline over the relatively short 3-year follow-up.”
Co-author Professor Marilyn Albert from Johns Hopkins University School of Medicine, USA, adds, “We eagerly await the follow-up of ACHIEVE that is currently underway to examine the longer-term effects of hearing aids on cognition in populations at lower risk of dementia. Further analyses of MRI and social engagement data will also improve our understanding of the ways in which hearing aids may help delay cognitive decline.”
Despite some limitations in the study, such as potential bias due to the inability to mask participants and researchers to the intervention, the results provided robust evidence that treating hearing loss may be a potent tool to protect cognitive function and delay dementia diagnoses, especially for older adults at a higher risk of cognitive decline.
The findings support the 2020 Lancet Commission on Dementia’s conclusions, which estimated that untreated hearing loss could contribute to around 8% of dementia cases worldwide. Treating age-related hearing loss could supplement existing national dementia risk reduction strategies, making hearing aids a potentially vital tool for populations at risk of dementia.
While the study’s results are promising, the authors emphasize the need for longer-term follow-ups to examine the prolonged effects of hearing aids on cognition, particularly in populations at lower risk of dementia.
Additionally, further trials in different settings, focusing on purposively sampled high-risk populations for cognitive decline and dementia, are urgently required.
Writing in a linked Comment, Professor Gill Livingston from University College London, UK (who was not involved in the study) says, “We also need long-term follow-up of ACHIEVE to see if the hearing intervention results in cognitive differences over time, particularly in healthy volunteers. Finally, we urgently need more trials in other settings, using the lessons learnt about the need to focus on purposively sampled populations at high risk of cognitive decline and dementia. Overall, the findings from this study are hopeful. Hearing aids could really make a difference for populations at risk of dementia.”
In conclusion, the study adds to the growing evidence that addressing hearing loss could be a crucial global public health target for dementia prevention efforts. Hearing aids have the potential to make a significant difference in the lives of older adults at risk of cognitive decline and may pave the way for new strategies in the fight against dementia.
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