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OUTCOMES RESEARCH IN REVIEW
Hearing Impairment: Another Microvascular Complication of Diabetes?
BainbridgeKE,HoffmanHJ,CowieCCDiabetesandhearingimpairmentintheUnitedStates:audiometricevidencefrom theNationalHealthandNutritionExaminationSurvey,1999to2004AnnInternMed2008;149:110
Study Overview Objective To determine whether diabetes is related to hearing impairment Design Cross-sectional study Setting and participants 5140 participants aged 20 to 69 years who had audiometric testing and completed a diabetes questionnaire as part of the National Health and Nutrition Examination Study NHANES from 1999 to 2004 A diagnosis of diabetes was assessed with the question, Other than during pregnancy for women, have you ever been told by a doctor or health professional that you have diabetes or sugar diabetes? 2259 participants were randomly assigned to fasting blood glucose testing; of these participants, 146 had diabetes A total of 399 participants in the cohort had diabetes either self-reported or confirmed by blood glucose testing Main outcome measure Mild or greater severity hearing loss at low or mid and high frequencies in the worse ear as measured by audiometric testing Main results Of
participants with diabetes, 213 95 confidence interval [CI], 15275 had mild or greater severity hearing loss at low or mid frequency in the worse ear as compared with 94 95 CI, 82105 of those without diabetes Similarly, 541 95 CI, 459623 of participants with diabetes versus 32 95 CI, 305335 of those without diabetes had mild or greater severity hearing loss at high frequencies in the worse ear Results were significant P 0001 and were adjusted for other factors that might explain hearing loss, such as age, use of ototoxic medications, smoking status, military history, sex, race/ ethnicity, education, and noise exposure adjusted odds ratio for low-/mid-frequency and high-frequency impairment of mild or greater severity, 182 [95 CI, 127260] and 216 [95 CI, 147318], respectively Similar results were found for moderate or greater severity hearing impairment and for hearing impairment in the better ear In a subset of participants with measured fasting glucose level, results were consistent and demonstrated a dose-response, such that hearing impairment was more common in participants who met diagnostic criteria for diabetes or had impaired fasting glucose as compared with participants
with normal glucose levels 484 and 405 vs 304, respectively Conclusion Diabetes is associated with hearing impairment Commentary Extensive research has documented a strong link between microvascular disease eg, nephropathy, retinopathy, neuropathy and diabetes [1,2], and studies have shown that the risk for microvascular disease can be lowered with intensive glucose control [3,4] Hearing impairment has not been considered a microvascular complication of diabetes, but the results of this study could compel an eventual change if future research confirms the findings of this study by Bainbridge and colleagues
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Outcomes Research in Review Section editorS
Ashish K Jha, MD, MPH Brigham and Womens Hospital Boston, MA Ula Hwang, MD, MPH Mount Sinai School of Medicine New York, NY Salomeh Keyhani, MD, MPH Mount Sinai School of Medicine New York, NY Nirav R Shah, MD, MPH New York University School of Medicine New York, NY Mark W Friedberg, MD, MPP Brigham and Womens Hospital Boston, MA Asaf Bitton, MD Brigham and Womens Hospital Boston, MA Marc M Triola, MD New York University School of Medicine New York, NY Jason P Block, MD, MPH Brigham and Womens Hospital Boston,
MA
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OUTCOMES RESEARCH IN REVIEW
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Linking diabetes and hearing impairment is plausible for the same reasons that diabetes is known to cause microvascular disease Glycosylation of the microvasculature, such as in the retina, peripheral nerves, and kidney, progressively damages the vessels and disrupts the function of the tissues that these vessels supply Similarly, prior research has documented pathologic changes consistent with glycosylation in the nerves of the inner ear in diabetic patients [5,6]; however, observational evidence of an association between hearing loss and diabetes has been weak Dalton et al [7] found slightly higher rates of age-related hearing loss presbycusis among diabetic patients Hearing loss was more common among patients who had already been diagnosed with neuropathy Results of a similar evaluation in the Framingham Heart Study showed more equivocal results; an association between low-frequency hearing loss and increasing glucose level was present for women only [8] In this study by Bainbridge et al, a large divergence in hearing loss was found between participants with and without
diabetes using data from the NHANES surveys from 1999 to 2004 The association was seen for all frequencies of hearing loss, in better and worse ears, and for different severities of hearing loss, even after adjusting for clearly recognized potential confounders eg, noise exposure, ototoxic medications, smoking The authors assessed this relationship in multiple ways by including assessments of measured and self-reported hearing loss and diabetes, finding associations in each The study had several limitations First, authors were unable to distinguish between patients with type 1 and type 2 diabetes, so there is no way to discern if the relationship differs by diabetes type Second, diabetes was self-reported in the main analysis Although the study included a subsample of participants who underwent fasting blood glucose testing, this subset comprised less than half of the total study population Also, data are cross-sectional and a temporal association cannot be established Finally, no measurements of diabetes control were provided, and concomitant microvascular diagnoses were not evaluated If hearing impairment is indeed a microvascular complication of diabetes, then one would expect
hearing impairment to coincide with retinopathy, neuropathy, or nephropathy Extensive measurements of potential microvascular complications of diabetes are provided in the NHANES surveys, and the authors should have been able to compare hearing loss with these complications Future research should examine hearing impairment
and diabetes in a longitudinal study assessing the relationship with degree of diabetes control and the coexistence of microvascular complications Clinical trials ultimately could provide concrete evidence of an association between hearing impairment and diabetes, similar to what has been established with diabetes and microvascular disease [1,2] Applications for Clinical Practice Based on data from this large, cross-sectional, nationally representative study, diabetes appears to be associated with hearing impairment If this association is confirmed in future studies, aggressive glucose control might be an effective strategy for preventing hearing impairment Clinicians should also be aware that diabetic patients might be more likely to develop hearing impairment so that early audiometric testing can be pursued in patients at
risk
–ReviewbyJasonPBlock,MD,MPH
References
1 Turner R, Cull C, Holman R UK Prospective Diabetes Study 17: a 9-year update of a randomized, controlled trial on the effect of improved metabolic control on complications in noninsulin-dependent diabetes mellitus Ann Intern Med 1996;124 1 Pt 2:13645 2 Klein R, Klein BE, Moss SE Relation of glycemic control to diabetic microvascular complications in diabetes mellitus Ann Intern Med 1996;1241 Pt 2:906 3 Intensive blood-glucose control with sulphonylureas or insulin compared with conventional treatment and risk of complications in patients with type 2 diabetes UKPDS 33 UK Prospective Diabetes Study Group [published erratum appears in Lancet 1999;354:602] Lancet 1998;352:83753 4 The effect of intensive treatment of diabetes on the development and progression of long-term complications insulindependent diabetes mellitus The Diabetes Control and Complications Trial Research Group N Engl J Med 1993;329:97786 5 Makishima K, Tanaka K Pathological changes of the inner ear and central auditory pathway in diabetics Ann Otol Rhinol Laryngol 1971;80:21828 6 Jorgensen MB The inner ear in diabetes mellitus Histologic studies Arch Otolaryngol
1961;74:37381 7 Dalton DS, Cruickshanks KJ, Klein R, et al Association of NIDDM and hearing loss Diabetes Care 1998;21:15404 8 Gates GA, Cobb JL, DAgostino RB, Wolf PA The relation of hearing in the elderly to the presence of cardiovascular disease and cardiovascular risk factors Arch Otolaryngol Head Neck Surg 1993;119:15661
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