Hyperglycaemia – high blood sugar – is not only associated with hearing loss but is likely to be a direct cause of it, according to a large genetic study that strengthens the case for hearing monitoring in people with diabetes.
The researchers from Taiwan, the UK and the US said the findings support integrating hearing surveillance into diabetes management, particularly as the prevalence of hearing loss and type 2 diabetes continues to increase with ageing populations.
The study was published in BMJ Open on 8 June 2026.
The authors concluded that early and rigorous glycaemic control may represent an important strategy for preserving hearing alongside reducing other well-established complications of diabetes.
They used a two-sample Mendelian randomisation (MR) approach to investigate whether hyperglycaemia has a causal effect on hearing loss. The researchers said that unlike conventional observational studies, MR analyses use naturally occurring genetic variations to reduce the influence of confounding factors and reverse causation.
They analysed genetic data from the Taiwan Biobank, involving more than 145,000 participants, together with genome-wide association study (GWAS) data from Asian and European populations.
They examined the effects of three measures of hyperglycaemia – glycated haemoglobin (HbA1c), fasting blood glucose and type 2 diabetes – on both non-specific hearing loss and specific subtypes, including sensorineural, age-related and conductive hearing loss.
The analysis found that higher HbA1c, elevated fasting glucose and type 2 diabetes all significantly increased the risk of hearing loss. Depending on the measure examined, hyperglycaemia increased the risk by as much as 54%.
The strongest association was seen with HbA1c, where genetically predicted higher levels were associated with a 54% increased risk of hearing loss. Elevated fasting glucose increased risk by up to 45%, while type 2 diabetes was associated with a 13% higher risk.
Importantly, the findings remained significant after adjusting for other metabolic risk factors including smoking, blood pressure, blood lipids and body mass index.
One way relationship
The researchers also found evidence that the relationship was one-way, with hyperglycaemia increasing the risk of hearing loss rather than hearing loss influencing blood sugar levels.
“The findings emphasise the clinical importance of glycaemic control in hearing preservation strategies,” the authors wrote.
They said the consistent results across different populations and hearing loss subtypes provided strong genetic evidence that “chronic hyperglycaemia is an independent and modifiable driver of auditory decline”.
Previous observational studies had suggested a relationship between diabetes and hearing loss, but it had remained unclear whether high blood sugar itself caused hearing damage or whether the association was explained by other shared risk factors, they said.
The authors said their study overcame many of these limitations by using genetic variants as proxies for lifelong exposure to elevated blood glucose.
The researchers called for future studies using objective audiometric testing rather than self-reported hearing outcomes, as well as research in more diverse populations, including African, Hispanic and Indigenous groups.
Further work incorporating continuous glucose monitoring and multi-omics technologies could help clarify the biological mechanisms linking hyperglycaemia with hearing damage, including the roles of cochlear microvascular dysfunction, oxidative stress and the accumulation of advanced glycation end-products, they said.
