Diabetics of all ages are at increased likelihood of having hearing loss or deafness. Compared to people of the same age, younger diabetics are at higher risk of hearing loss; in terms of absolute risk, older diabetics are at higher risk (because nondiabetics are more likely to have hearing loss as they get older).
Some of this increase in risk is due to diabetes (hearing loss as a complication) and some of it is because of syndromes that include both hearing loss and diabetes (such as mitochondrial diabetes).
While some studies have not shown major hearing loss in diabetics, I find the evidence overwhelming. In some studies, a quarter of children with diabetes have at least mild hearing loss, meaning that they need a sound to be at least 25 decibels in some of the more commonly used frequencies, before they can hear it.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3214300/ - about children in Iran
http://www.ncbi.nlm.nih.gov/pubmed/23150692 - about adults in Brazil
http://www.indianpediatrics.net/jan2005/jan-15-21.htm - about Sudanese children (with poor metabolic control)
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3120175/ - about US adult diabetics (mostly type 2, and two thirds hearing impaired)
I kind of wonder if this means we should have more hearing screenings. Is hearing loss a problem if you don't notice a problem? I wonder if I have high frequency hearing loss.