Design
Case-control study.

Patients
A consecutive sample of 52 patients: 30 patients who met the National Institute of Neurological and Communicative Disorders and Stroke/Alzheimer's Disease and Related Disorders Association criteria for probable Alzheimer disease (group 1) and 22 patients with other forms of cognitive impairment (group 2).

Methods
Patients underwent a hearing screening that included a case history, a visual inspection of the external ear canal and tympanic membrane, and pure tone audiometry. Patients and their caregivers completed a questionnaire intended to assess hearing impairment and perceived disability.

Outcome Measures
Pass or fail on pure tone audiometry and pass or fail on a hearing impairment questionnaire.

Results
Of the 52 patients, 49 had significant hearing loss. No difference was found in the failure rate between patients in groups 1 and 2. In group 1, a significant discrepancy was found between the patient's self-report and that of their caregivers, whereas in group 2, the self-report was reliable. The prevalence of hearing loss in this population greatly exceeds the prevalence in healthy aged controls.

Conclusion
The extraordinarily high prevalence of hearing loss in this selected population suggests that a hearing evaluation should be part of any assessment of cognitive function.