Speech-in-noise hearing impairment is associated with an increased risk of incident dementia in 82,039 UK Biobank participants, Stevenson et al

The Lancet Commission report on dementia prevention, intervention and care identified hearing impairment as a major risk factor for dementia, and therefore there is an increased risk for dementia to occur in people who experience difficulties with their hearing.¹

Studies often assess hearing function using pure tone audiometry; this measures the ability to hear pure tones in a controlled and quiet environment. This, however, does not provide a full picture of someone’s hearing function. An alternative, and complementary, assessment involves measuring the ability to discern speech in a noisy background environment. This speech-in-noise (SiN) hearing assessment is used less than pure tone audiometry yet may better reflect someone’s hearing function in a day-to-day, real-world setting.      

Stevenson and colleagues have conducted the largest study to date exploring the association between SiN hearing and newly diagnosed dementia.² Over 82 000 people from the UK were included in the study and followed-up for 11 years; these people were aged 60 years or over and did not have dementia at the start of the study. Of these people, 82.5% had ‘normal’ SiN hearing, 13.8% had ‘insufficient’ SiN hearing and 3.7% had ‘poor’ SiN hearing at the start of the study. Over the course of the study, 1285 of these people developed dementia. Statistical models showed that ‘insufficient’ and ‘poor’ SiN hearing were significantly linked to a higher risk of developing dementia in the studied population (a 61% and a 91% increase in risk, respectively).

The authors took the analysis one step further because they also assessed factors that might have influenced the observed association between SiN hearing and dementia. These included: reverse causation, that is the possibility that people may have had unidentified early signs of dementia, which could have in turn affected hearing ability during the assessments; and the possibility that social isolation and depression may have mediated the observed hearing outcomes. The authors found limited evidence to suggest that either of these factors may have accounted for the increased risk of dementia with SiN hearing impairment.

An important limitation of this study was the retrospective use of hospital in-patient and death records to capture the onset of dementia. Although this type of methodology has been successfully used in the past, it does not completely preclude the possibility of a misclassification bias.

The authors conclude that SiN hearing impairment is associated with a higher risk of dementia although they fully support the need for larger prospective studies to evaluate this association further. If supported by additional studies, addressing SiN hearing impairment may become increasingly important to help prevent the onset of dementia.   

References

1. Livingston G et al. Dementia prevention, intervention, and care: 2020 report of the Lancet Commission. Lancet 2020;396:413–46.
2. Stevenson JS et al. Speech-in-noise hearing impairment is associated with an increased risk of incident dementia in 82,039 UK Biobank participants. Alzheimers Dement 2021; Jul 21. doi: 10.1002/alz.12416. Online ahead of print.