ABSTRACT
This study was an observational case–control study on type 2 DM disease and hearing in which both the diabetic and control groups were matched for age and sex. It showed a strong relationship between type 2 DM disease and hearing as the diabetic group had a significantly higher prevalence of hearing impairment than the general population. Both sexes were equally affected in the diabetic group. In the control group, males were more affected than females. Non-Saudi male and female diabetics had the most significant difference in prevalence of hearing loss.
The prevalence of hearing loss in the low, mid and high frequencies was significantly higher in the diabetic group than the control group for both better and worse hearing ears. Females were found to have a higher prevalence of hearing loss at low frequencies than males had in both diabetic and control groups.
The diabetic group were found to be more hearing impaired than the control group in both ears. It was found that the diabetic and control groups did not differ significantly in the hearing thresholds in the high frequencies in the better hearing ears. The diabetic group had poorer thresholds in the low, mid and high frequencies than the control group in the worse hearing ears. Gender was found to have no significant effect on the hearing thresholds.
A significant correlation was found in this study between age and hearing loss for both the better and worse hearing ears and in both the diabetic and study groups. No correlation was observed between the duration of DM and the degree of hearing loss.
Different audiogram shapes found in the study included flat, high frequency gently sloping, high frequency steeply sloping, low frequency ascending, inverted trough and some with no fit. No significant difference was found between groups in the type of audiogram shape.
It has shown in this study that the site of hearing loss was the cochlea. No significant relationship was found between family history of diabetes in the diabetic subjects and degree of hearing loss. It was found that the diabetic group in this study had a higher prevalence of family history of diabetes than the control group. This indicated genetic factors are involved in the development of type 2 DM.
There was a significant relationship between degree of hearing loss and complications for both worse and better hearing ears. Cataracts did show a significant relationship to degree of hearing loss for both worse and better hearing ears. Neuropathy and hyperlipidaemia were found to have a significant effect on hearing loss in diabetics. Other complications, such as hypertension, heart diseases, renal disorders and diabetic foot did not show any significant relationship with hearing loss. Fewer complications were observed in diabetic patients on diet. It was found that the diabetic patients who were treated by diet or by diet and hypoglycaemic agents had better hearing thresholds than those treated by hypoglycaemic agent or insulin. Finally in this study, it was found that good hypoglycaemic control was related significantly to degree of hearing in the worse hearing ear only. It is concluded that there are several factors that may present a risk to development of hearing loss in type 2 DM disease. These are age, microvascular complications, peripheral neuropathy, hyperlipidaemia, diet and hypoglycaemic control.
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