By Seema Gupta, MD, MSPH

Clinical Assistant Professor, Department of Family and Community Health, Joan C. Edwards School of Medicine, Marshall University, Huntington, WV

Dr. Gupta reports no financial relationships relevant to this field of study.

SYNOPSIS: A large-scale retrospective cohort study found that iron deficiency anemia was associated positively with sensorineural hearing loss and combined hearing loss.

SOURCE: Schieffer KM, Chuang CH, Connor J, et al. Association of iron deficiency anemia with hearing loss in U.S. adults. JAMA Otolaryngol Head Neck Surg 2016 Dec 29. doi: 10.1001/jamaoto.2016.3631. [Epub ahead of print].

Worldwide, iron deficiency is a major public health challenge, especially in women of childbearing age, children, and those living in poverty. Iron deficiency anemia (IDA) occurs when iron deficiency becomes significant enough to diminish erythropoiesis, resulting in the development of anemia. Although iron deficiency caused solely by diet is uncommon in adults in North America and Europe, it is most common in women of childbearing age and as a manifestation of hemorrhage. In the United States, data indicate 9-11% of women of adolescent and/or childbearing age suffer from iron deficiency, while IDA may exist in approximately 2-5% of these individuals.1 The prevalence of iron deficiency also correlates with the state of pregnancy as well as with a greater number of pregnancies.2 In contrast, the prevalence of hearing loss in the United States population is quite widespread. In fact, data estimates show that approximately 12.7% of Americans 12 years of age suffered bilateral hearing loss from 2001-2008, and this estimate increased to approximately 20.3% when individuals who suffered unilateral hearing loss also were included.3 Additionally, the prevalence of hearing loss is expected to rise as the population ages. Hearing loss increases with each decade of life, affecting 40-66% of adults > 65 years of age and 80% of those > 85 years of age. Sudden sensorineural hearing loss (SNHL) is a type of permanent hearing loss in which the vestibular cochlear nerve, inner ear, or central processing centers of the brain are suddenly affected, leading to a rapid deterioration of the hearing function in less than a 72-hour period. Risk factors for earlier onset of adult hearing loss may include hypertension, diabetes, and tobacco use. Interestingly, recent research has found a significant association between sudden SNHL and prior IDA.4

In their research, Schieffer et al conducted a retrospective study involving 305,339 adults 21-90 years of age living in the United States. Of the patients in the study population, approximately 43% of those patients were men, and the mean age was 50 years. The researchers assessed the prevalence of IDA and hearing loss in this population, including SNHL, conductive hearing loss, and combined hearing loss. The study revealed a 1.6% prevalence of combined hearing loss and 0.7% prevalence of IDA. Both SNHL (present in 1.1% of individuals with IDA; P = 0.005) and combined hearing loss (present in 3.4% individuals with IDA; P < 0.001) were significantly associated with IDA. Furthermore, a logistic regression analysis confirmed that the overall risk for SNHL in someone with IDA was 82% higher than for those without IDA (adjusted odds ratio [OR], 1.82; 95% confidence interval [CI], 1.18-2.66). Individuals with IDA also had a 2.4 times greater risk of combined hearing loss (adjusted OR, 2.41; 95% CI, 1.90-3.01) compared to those without IDA, after adjusting for sex.

COMMENTARY

With a well-conducted, large retrospective study, the authors made a strong case for the existence of an association between IDA in adults and hearing loss. There may be several potential mechanisms by which IDA may affect hearing health. Although the role of iron in the inner ear has not been clearly established, vascular supply to this area is critical. IDA may exacerbate conditions, leading the cochlear area to become susceptible to ischemic damage. The study results raise concerns about the potential role of iron in the vasculature and nervous system and, thus, the possibility of its association with other common types of adult hearing loss beside SNHL. Although IDA has been demonstrated to be a potential risk factor for ischemic stroke due to lower hemoglobin levels, leading to impaired oxygen-carrying capacity, the increased risk of IDA in patients with reactive thrombocytosis may be another potential vascular mechanism that may relate IDA to hearing loss.5,6

As iron deficiency, as well as the resultant anemia, can be treated easily with several months of oral iron supplementation in most cases, the real clinical question remains whether early diagnosis and treatment of IDA or iron deficiency could positively affect the overall health status of adults with hearing loss or even prevent hearing loss. Additional studies surely are needed to determine whether there is a link between iron supplementation and improving the hearing status in adults. Meanwhile, it would make clinical sense to continue to diagnose and treat iron deficiency while knowing that we may be preventing potential hearing loss. For everyone else, we can reiterate that a healthy, well-balanced diet that meets the daily recommended intake of vitamins and nutrients such as iron not only may help in physical and mental well-being but also potentially with hearing health by preventing premature, permanent hearing loss.

REFERENCES

  1. Looker AC, Dallman PR, Carroll MD, et al. Prevalence of iron deficiency in the United States. JAMA 1997;277:973-976.
  2. Mei Z, Cogswell ME, Looker AC, et al. Assessment of iron status in U.S. pregnant women from the National Health and Nutrition Examination Survey (NHANES), 1999-2006. Am J Clin Nutr 2011;93:1312-1320.
  3. Lin FR, Niparko JK, Ferrucci L. Hearing loss prevalence in the United States. Arch Intern Med 2011;171:1851-1852.
  4. Chung SD, Chen PY, Lin HC, Hung SH. Sudden sensorineural hearing loss associated with iron-deficiency anemia: A population-based study. JAMA Otolaryngol Head Neck Surg 2014;140:417-422.
  5. Dubyk MD, Card RT, Whiting SJ, et al. Iron deficiency anemia prevalence at first stroke or transient ischemic attack. Can J Neurol Sci 2012;39:189-195.
  6. Franchini M, Targher G, Montagnana M, Lippi G. Iron and thrombosis. Ann Hematol 2008;87:167-173.