Assessing and managing hearing loss: Where is the evidence to support clinical practice?

Hearing loss – a large disease burden

One in six people in the UK has a hearing difficulty and this is set to increase to one in five by 2035. Hearing loss is actually the most prevalent sensory deficit and is ranked fourth for years lived with a disability. It causes communication difficulties, frustration, and is associated with social isolation, depression and cognitive decline. Good communication skills are required for children to grow well, for adults to live well and for older people to age well. Therefore, assessing and managing hearing loss is a priority for the NHS. But, where is the evidence to support clinical practice?

Our professional bodies and societies have published a plethora of good practice guidelines. However, there has always been an uneasy suspicion that much of our clinical practice lacks a foundation of high-quality research evidence. The 2018 National Guideline on Hearing Loss in Adults by the National Institute for Health and Care Excellence (NICE) confirmed this suspicion.

NICE guideline on hearing loss in adults

The scope for the NICE guideline was developed in consultation with stakeholders and this process identified the key areas to be addressed. The committee developed around 20 review questions to address these key areas. For example, one review question investigated the benefit of providing someone with a single hearing aid or with two hearing aids, one for each ear. After a process of identification, screening, and eligibility checks, four studies were identified that addressed this particular clinical research question. The next step was to assess the quality of the evidence contained within these studies. For intervention studies, the highest quality studies are generally Randomised Control Trials (RCTs), where a sample from the population is randomised to the treatment and control groups, preferably blinded to both the participant and the researcher, in order to reduce any potential bias. Within hearing health care, there are few RCTs and this immediately reduces the quality of the overall evidence.  In the example above, the overall quality was assessed as very low. This means there was insufficient evidence to determine if there are clinically important benefits of two versus one hearing aid. In the absence of high quality evidence, recommendations are based on moderate or low quality evidence along with the views and opinions of the guideline committee. In this example, the committee recommended that two hearing aids should be offered to everyone with aid-able hearing in each ear.

Alarmingly, for 50% of the research questions addressed in the guideline, there was either no evidence or the quality of evidence was assessed as low or very low. The quantity of studies that are identified in NICE guidelines varies greatly and for some topics e.g. pain management, there are many studies. The quality of studies also varies greatly but, for some topics e.g. cardiovascular disease, there are examples of large studies of good quality.

When areas were identified for which good evidence was lacking, the committee included research recommendations based on national priorities, the importance to patients, potential impact to the NHS and ethical (and technical) feasibility. Research recommendations include identifying if hearing aids reduce dementia and the effectiveness of monitoring and follow-up.

What next?

The NICE guideline has undoubtedly increased the national profile of hearing loss. However, the evidence on which recommendations are based is limited in quantity and quality. Within Manchester BRC, we are working hard to provide the evidence.

Our research programme builds on new discoveries in prevention of hearing loss, diagnosis and intervention.

By way of example: we are developing new hearing assessment methods for infants, a pharmacogenetic (drug/gene) point-of-care test to prevent  deafness by drug related damage to the inner ear (ototoxicity), and using digital technology for internet screening and remote health interventions.

Clinical support and expertise offered by NIHR Manchester Clinical Research Facility will help to facilitate our research as we drive hearing health improvements and lasting change for all, through life-changing research that bridges the gap between new discoveries and individualised care.

Acknowledgement

The guideline referred to in this article was produced by the National Guideline Centre for the National Institute for Health and Care Excellence (NICE). The views expressed in this article are those of the author and not necessarily those of NICE.