Type 2 diabetes is associated with hearing impairment review finds

Type 2 diabetes could be linked to problems with hearing due to damage caused to the auditory system, according to a new review.
Hearing impairment has been linked to type 2 diabetes, and American researchers Dr Elizabeth Helzner and Dr Kevin J. Contrera set about investigating this relationship in several population-based studies.
The scientists analysed studies such as the National Health and Nutrition Examination Study (NHANES) and concluded that “an association between diabetes and hearing impairment in human subjects has been shown in many, but not all, studies”.
Certain studies suggested that people with type 2 diabetes are predisposed to hearing impairment in higher frequencies. Helzner hypothesised that this association could exist due to the combination of hyperglycemia and oxidative stress to cochlear microangiopathy and auditory neuropathy.
“There is convincing evidence that diabetes-induced microangiopathy, neuropathy, and mitochondrial damage contribute to damage to the auditory system,” said Helzner.
The association between type 2 diabetes and hearing impairment (HI) tended to be stronger among younger participants, but the researchers believe this might have been because other causes of age-related hearing impairment masked the contribution of type 2 diabetes among older samples.
“Based on the evidence on prevalence of HI among patients with diabetes presented here, it is prudent for clinicians to incorporate auditory function testing as part of the medical management of type 2 diabetes,” Helzner added.
However, the researchers pointed out that direct comparison between studies was complicated due to a lack of consistency in defining hearing impairment. Therefore, “the temporal (and therefore, causal) relationship between diabetes and hearing impairment has not been clarified”.
They concluded that longitudinal studies are required to assess whether patients with type 2 diabetes are at an increased risk of early-onset hearing impairment, and how the careful management of diabetes could potentially reduce this risk.
The findings were published in the journal Current Diabetes Reports.