RELATIONSHIP BETWEEN HEARING LOSS AND HBA1C LEVELS IN DIABETIC PATIENTS: A TERTIARY CARE HOSPITAL-BASED STUDY

Abstract

 Background: Diabetes mellitus (DM) is increasingly recognized as a risk factor for sensorineural hearing loss (SNHL). Elevated glycosylated hemoglobin (HbA1c) levels may be associated with cochlear microangiopathy, leading to auditory dysfunction. This study examined the relationship between hearing loss and HbA1c levels among diabetic patients attending a tertiary care hospital, and evaluated the influence of demographics, subjective symptom severity, audiometric parameters, associated symptoms (tinnitus, vertigo), and diabetes treatment regimens on hearing outcomes. Methods: In this hospital-based cross-sectional observational study, 236 patients with type 2 diabetes mellitus aged 18–75 years attending the ENT and Endocrinology outpatient departments between 2023 and 2025 were evaluated for hearing impairment. Demographic data including age and gender were recorded. Clinical history focused on subjectively perceived hearing loss graded as mild, moderate, or severe, along with associated tinnitus and vertigo. Pure Tone Audiometry (PTA) was performed at frequencies of 0.5–4 kHz, and hearing loss was categorized as 20–30 dB, 30–40 dB, and 40–50 dB. Air–Bone Gap (ABG) was documented in ranges of 10–20 dB, 20–30 dB, and 30–40 dB. Glycemic control was assessed using HbA1c levels, grouped as 5–6%, 6–7%, and ≥7%. Diabetes treatment modalities (diet control, oral hypoglycemic agents, and insulin therapy) were noted. Hearing aid prescription and subjective post-intervention improvement using functional hearing assessment were also evaluated. Statistical analysis included chi-square test and Pearson correlation, with p < 0.05 considered statistically significant.

Results: A total of 236 patients were included, with a mean age of 47.6 ± 9.8 years. The study population comprised 138 males (58.5%) and 98 females (41.5%). Subjective hearing loss was reported as mild in 98 patients (41.5%), moderate in 86 (36.4%), and severe in 52 (22.1%). Pure tone audiometry revealed hearing thresholds of 30–40 dB in 88 patients (37.3%), followed by 40–50 dB in 76 patients (32.2%) and 20–30 dB in 72 patients (30.5%), with a mean PTA of 34.9 ± 8.2 dB. ABG values of 20–30 dB were most prevalent (40.7%), particularly among patients with poorer glycemic control. HbA1c levels ≥7% were observed in 90 patients (38.1%) and were significantly associated with worsening PTA and ABG values compared to patients with HbA1c ≤6% (p < 0.001). Tinnitus was present in 98 patients (41.5%) and vertigo in 64 patients (27.1%), with higher prevalence among those with moderate to severe hearing loss. Among treatment groups, subjective hearing improvement was noted in 71.4% of patients on diet control alone, 69.2% on oral hypoglycemics, and 51.1% on insulin therapy. Hearing aids were prescribed to 76 patients (32.2%), predominantly among those with moderate to severe hearing loss. A significant positive correlation was observed between increasing HbA1c levels and severity of hearing loss (p < 0.01).

 Conclusion: This study provides compelling evidence that hearing loss in diabetic patients is strongly and positively associated with poor glycaemic control, as reflected by elevated HbA1c levels. The use of objective audiological parameters—such as PTA thresholds, air–bone gap measurements, and associated symptoms like tinnitus and vertigo—strengthens the validity of the findings. Patients with HbA1c values ≥7% consistently demonstrated higher degrees of hearing impairment, greater subjective disability, and increased need for audiological rehabilitation.