From the Guidelines
The World Health Organization (WHO) grades hearing loss based on pure-tone average thresholds measured in decibels (dB), with normal hearing defined as 25 dB or better in both ears, and disabling hearing loss considered to be greater than 40 dB in adults and greater than 30 dB in children, as supported by the most recent evidence 1.
Key Points
- The WHO grading system helps clinicians quantify hearing impairment severity, guide appropriate interventions, and monitor progression over time.
- The classification is based on the average of hearing threshold levels at 500,1000,2000, and 4000 Hz frequencies, which represent the most important range for speech understanding.
- Early identification of hearing loss through this standardized grading system allows for timely intervention with hearing aids, cochlear implants, or other assistive devices, potentially preventing communication difficulties, social isolation, and cognitive decline associated with untreated hearing loss.
Grading System
- Normal hearing: 25 dB or better in both ears
- Slight/mild hearing loss: 26-40 dB
- Moderate hearing loss: 41-60 dB
- Severe hearing loss: 61-80 dB
- Profound hearing loss: 81 dB or greater
Importance of Early Identification
- Early identification of hearing loss is crucial for timely intervention and prevention of communication difficulties, social isolation, and cognitive decline associated with untreated hearing loss, as highlighted in the study 1.
- The WHO grading system provides a standardized framework for clinicians to quantify hearing impairment severity and guide appropriate interventions, as supported by the evidence 1.
From the Research
WHO Grading of Hearing Loss
The World Health Organization (WHO) grading system for hearing loss is a widely used classification system to categorize the severity of hearing impairment.
- The system categorizes hearing loss into five grades, ranging from 0 to 4, with cut-off values of ≤25 dB NHL, 26-40 dB NHL, 41-60 dB NHL, 60-80 dB NHL, and ≥81 dB NHL 2.
- A study evaluating the WHO-proposed hearing-impairment grading system found that each step in the progression from "normal" to "severe" led to a significant difference in functional communication, with moderate to very large effect sizes between each successive step 3.
- The WHO grading system has been validated with evidence from studies of functional communication in older adults, with the system showing a significant association between the grade of hearing loss and functional communication abilities 3.
Application of the WHO Grading System
The WHO grading system has been applied in various studies to assess hearing loss in different populations, including:
- Older adults with age-related hearing loss, where the system was found to be valid and reliable in categorizing the severity of hearing impairment 3.
- Dogs with chronic otitis externa or otitis media, where the system was used to categorize hearing loss and assess the suitability of dogs for medical or surgical therapy 2.
- Patients with sudden deafness, where a grading system established by the Japanese Ministry of Health and Welfare was used to classify cases and evaluate hearing recovery 4.
Key Findings
- The WHO grading system is a useful tool for categorizing the severity of hearing impairment and assessing functional communication abilities 3.
- Higher grades of hearing loss are significantly associated with poorer functional communication and greater impairment in daily life 3.
- The system has been validated in various populations, including older adults and dogs with chronic otitis externa or otitis media 3, 2.