20Q: Promoting Healthy Hearing Over the Lifespan - Considering Comorbidities

From the Desk of Gus Mueller

Jay Hall, PhD, is back with us again this month as the guest author of 20Q.  As you might recall, last month Jay took a critical look at our routine audiologic procedures, and discussed some ways that we can make this testing both more effective and efficient.  This month his focus is on the bigger picture of comorbid conditions associated with hearing loss and related disorders.

In the field of medicine, the term “morbidity” often is used to describe the condition of suffering from a disease or medical condition, or the rate of disease in a population.  As the name suggests, comorbidity then is the simultaneous presence of two or more diseases or medical conditions in a patient.

Obesity, at least in the U.S., is probably the leading factor to predispose people to comorbid illnesses. In fact, according to the Obesity Medicine Association, there are over 200 medical problems (including 13 types of cancer) linked with obesity.  Comorbidity also is common in psychiatric conditions.  Over 9 million adults in the U.S. have a comorbidity that includes substance abuse and a mental illness, or two types of mental illness such as anxiety and depression.

It has only been the last 15-20 years that we’ve seen much written about the comorbid conditions associated with hearing loss.  Recently, however, there has been considerable research related to social isolation, loneliness, cognition and dementia.  But there are many more comorbid conditions to consider, which is why we’ve brought in Dr. Hall to review them for us.

James W. “Jay” Hall III, PhD, holds academic appointments from Salus University, the University of Hawaii, and the University of Pretoria South Africa.  He is internationally recognized for his research, publications and workshops.  His home office is in his home state of Maine, where his penchant for audiologic lecturing has branched out to neighborhood micro-breweries.

Dr Hall’s extensive publications span over 40 years, and cover a variety of audiologic topics.  Many of his books have become the go-to text for both students and clinicians. He is one of the founders of the American Academy of Audiology, served on the Academy’s Board of Directors, has held several leadership positions within the Academy, and has received the Academy’s Distinguished Achievement Award, Presidential Service Award and the Jerger Career Award for Research.

It's important for us to remember that in many cases, age-related hearing loss is not simply a consequence of getting older, but often is associated with other conditions.  You’ll find an excellent review of many of them in this month’s 20Q. 

Gus Mueller, PhD
Contributing Editor

Browse the complete collection of 20Q with Gus Mueller CEU articles at www.audiologyonline.com/20Q

20Q: Promoting Healthy Hearing Over the Lifespan - Considering Comorbidities

Learning Outcomes 

After reading this article, professionals will be able to:

• Define comorbidity and discuss how a disease or disorder are risk factors for hearing loss or causes hearing loss.
• List common diseases and disorders found in the adult audiology population.
• Discuss the connection between hearing problems and comorbid conditions.

James W. Hall III

1. Good to be back talking to you.  I recall that last month, at one point, you mentioned comorbid conditions. I’ve been thinking about that, and to be honest, I’m not very familiar with that term.

You’re not alone. Most audiologists don’t use the terms comorbidity or comorbid conditions in discussing patients. In medicine, the term comorbidity refers to two or more different diseases or disorders occurring in the same individual (Valderas et al., 2009). The diseases may occur by chance. That is, the diseases or disorders may be unrelated where one doesn’t play a role in causing the other. Health care professionals, including, audiologists are typically more interested in comorbidity when a disease or disorder is a risk factor for hearing loss or causes hearing loss.

2. I don’t remember hearing about comorbidity or comorbid conditions back in graduate school. Is there much research on comorbid conditions and hearing loss?

Good question. I recently performed a PubMed literature search (www.nlm.nih.gov) with keywords like “comorbid conditions,” “comorbidity,” “hearing,” and “hearing loss”. Believe it or not, there are over 1000 peer-reviewed publications on the topic, and almost all have appeared within the last ten years.

3. That’s an impressive number of publications. Since I’m a little behind on my journal reading, can you point out some of the comorbid conditions I should consider with my patients?

I would be happy to. There are at least two ways to put together a list of comorbid conditions related to hearing loss. Since I recall you said last month that you don’t see many children in your clinic, let’s focus on adult patients. One approach is to identify diseases and disorders affecting adult patients who come to an audiology clinic. Windmill & Freeman (2019) did just that in an analysis of Medicare data for over 1,000,000 patients seeking audiology services. Listed from most common to least common in an adult audiology population, the main diseases and disorders are:

• Cardiovascular diseases
• Hyperlipidemia (high cholesterol)
• Rheumatoid arthritis
• Diabetes
• Kidney disease
• Cognitive decline, including dementia
• Depression

4. That’s quite a list. Before we talk about these different diseases, what is the other way to consider comorbid conditions?

The other approach is to search the research literature for publications that describe specific comorbid conditions associated with hearing loss and related disorders like tinnitus. It’s quite simple to quickly find articles with, for example, keywords such as “diabetes” and “hearing loss.” Believe it or not, using the PubMed search engine that I just mentioned, your search will reveal almost 2500 peer-reviewed publications about hearing loss on that condition alone! I usually narrow down the field by including the keyword “review” in my search.

5. That’s a good idea. I don’t have enough time to sift through thousands of articles.

Most of us don’t have that kind of free time. A recent review article often provides just the right amount of new and old research information on a topic to keep you updated. In fact, as we were speaking, I conducted a more refined search that produced an excellent example of a 2021 paper by some Australian authors, “Diabetes mellitus and hearing: A review.” A free electronic copy of the article is readily available online in PDF format (Samocha-Bonet, Wu & Ryugo, 2021).

6. If you have some time now, maybe we could take a few minutes to talk about the connection between hearing problems and some of the comorbid conditions on your list?

Sure. Let’s begin with diabetes. The literature linking hearing loss to diabetes mellitus is remarkably large and rapidly expanding. Unfortunately, the prevalence of diabetes is also rapidly increasing, particularly in developed countries like the USA and the UK. Importantly, there’s a direct connection between the degree of hearing loss and the duration of diabetes since onset (e.g., Gupta et al., 2019; Kim et al., 2016). Not surprisingly, diabetes is often associated with other comorbid conditions, such as peripheral neuropathy, cardiovascular disease, or kidney disease, putting patients at risk for hearing loss (Meneses-Barriviera et al., 2018; Morrison et al., 2014).

7. Are there specific auditory tests you recommend for this patient population?

Absolutely. Dozens of clinical studies over the past 20 to 25 years confirm the value of otoacoustic emissions, particularly DPOAEs, in the documentation of cochlear dysfunction associated with diabetes mellitus (Nardo et al., 1998; Ortis Alborch et al., 1998; Ottavani et al., 2002; Yanhong et al., 2020), including children with type I diabetes and adults with the more common type II. Importantly, abnormal DPOAE findings offer an early sign of auditory dysfunction in diabetic people with normal hearing sensitivity (Spankovich, Long & Hood, 2019; Botelho, Carvalho & Silva, 2014; Park, Park & Choi, 2001). There’s even a meta-analysis paper summarizing DPOAE findings in people with type I diabetes from multiple studies (Mujica-Moto et al., 2018). You really should include DPOAEs in your test battery for any child or adult at risk for or with the diagnosis of diabetes.

8. The link between diabetes and auditory dysfunction seems clear. What are audiologists doing to encourage these people to get a hearing test?

The strong research evidence on diabetes as a comorbid condition has prompted some audiologists to increase efforts to educate physicians and the public about the connection between diabetes and hearing loss and other chronic health conditions. Readers are referred to the website www.theaudiologyproject.com for more information about this worthwhile effort. 

9. I noticed you listed cardiovascular diseases. What specific diseases are you referring to?

A variety of cardiovascular disorders and diseases put a person at risk for auditory dysfunction, including hypertension, ischemic heart disease, heart failure, atrial fibrillation, and stroke. One or more of the conditions are not uncommon in an older patient population seeking hearing health care (Windmill & Freeman, 2019). As Hull (2014) notes, audiologists should add questions about cardiovascular health to the patient’s case history. Cardiovascular disease is associated with a more rapid decrease of hearing sensitivity with aging, particularly for men (Wattamwar et al., 2018). As you would expect, cardiovascular diseases are also a major risk factor for central auditory dysfunction (Hall, 2021).

10. So, you’re saying that my patients with one or more of these cardiovascular diseases might have abnormal audiograms or problems with word recognition?

Some patients may have decreased pure-tone hearing thresholds or reduced scores on word recognition tests in quiet. Still, a more common finding is abnormalities in tests of central auditory function. Your test battery for this patient population really should include a measure of speech perception in noise. You could also add an objective test of central auditory function, such as comparing thresholds for contralateral versus ipsilateral acoustic reflexes.

11. I was surprised to see hyperlipidemia on your list. My dad takes atorvastatin for his high cholesterol. Should I be concerned about his risk for hearing loss?

High cholesterol, or hyperlipidemia, is a common health problem affecting over 30% of adults in the USA. It’s a well-known risk factor for cardiovascular disease, such as cerebrovascular accidents (strokes) and coronary artery disease leading to myocardial infarction (heart attacks). In addition, recent research confirms that high cholesterol is also a risk factor for hearing loss (Lee et al., 2020; Yucel et al., 2019, and a co-existing factor in sudden-onset sensorineural hearing loss (Chen et al., 2020). Fortunately, these and other studies offer evidence that Lipitor (atorvastatin) prevents hearing impairment for people like your dad (Hamid et al., 2014; Lee et al., 2020; Olsowy et al., 2007; Yucel et al., 2019). Audiology history forms should include questions about hyperlipidemia and whether the patient is under medical management.

12. In the last few years, I’ve heard quite a bit about hearing loss and cognitive impairment. I see that cognitive decline and dementia are on the list of comorbid conditions. Is the connection between cognitive function and hearing adequately supported with research?

Cognitive functions such as memory, attention, and processing speed play an integral role in hearing and processing auditory information. There is now increasing international scientific recognition of a link between peripheral hearing loss and cognitive impairment. Persons with unmanaged or “untreated” hearing loss have a greater likelihood of cognitive decline (Lin, 2011; Thomson et al., 2017; Hung et al., 2015; Loughrey et al., 2018; Mamo et al., 2018; Dawes, 2019; Taljaard et al., 2016).

13. Good to know. Any chance my typical air-bone-speech test battery will help me detect hearing problems related to cognitive decline?

Probably not. There is, however, a strong connection between central auditory processing and cognitive decline and dementia. This, of course, is not breaking news. Over 25 years ago, Strouse, Hall & Berger (1995) reported auditory processing disorders in patients with early-onset Alzheimer’s dementia. Subsequent studies confirmed that deficits in central auditory processing were among the earliest clinical signs of dementia (Gates et al., 1998). Now, there is substantial research evidence documenting a strong correlation between auditory processing, including performance on clinical tests of speech perception in noise, with impaired cognitive performance for attention, memory, and processing speed, and dementia. (e.g., Dryden et al., 2017; Thomson et al., 2017; Hung et al., 2015; Loughrey et al., 2018; Davis et al., 2016; Dawes et al., 2019).

14. Okay, I can probably include a test of speech perception in noise in my assessment of older patients who might have cognitive issues. But, I first need to get these patients into my office!

An audiologist’s knowledge about cognitive decline and hearing influences decisions about patient referrals and hearing assessment. Audiologists must reach out to medical disciplines that identify, diagnose, and manage patients with cognitive impairment and dementia, among them primary care physicians, neurologists, psychiatrists, and geriatric specialists, as well as otolaryngologists, psychologists, and neuropsychologists. These health professionals should appreciate the well-established relation between hearing loss and deteriorating cognitive function. Health professionals who take care of this patient population should recognize that you can routinely apply some common auditory measures, like speech-in-noise tests, to identify early stages of cognitive decline before the onset of dementia. Patients at risk for or diagnosed with cognitive impairment should routinely be referred for audiological assessment. Of course, audiologists who encounter patients who show clinical evidence of cognitive decline, such as difficulty grasping the task for simple auditory tests or poor performance of measures of auditory processing, should refer these patients to health professionals who specialize in cognitive services for proper evaluation and management.

15. We’ve talked about most of the comorbid conditions on the list. Are there any other co-existing or comorbid conditions related to hearing that I should look for in clinical practice?

Yes. You should keep an eye open for older patients with visual deficits. Audiologists are well-aware of the importance of visual skills for patients with peripheral hearing loss. Everyday face-to-face communication, including speech perception, is nearly always enhanced for patients who benefit from visual cues. Visual skills also may influence the outcome of auditory tests that involve a picture pointing task or that require reading visually presented material (test words or sentences) in speech audiometry.

16. Now that you mention it, most of my older patients wear glasses. Anything special that I should know regarding the connection between hearing and vision?

Dual sensory deficits, hearing, and vision loss in combination are quite prevalent in older adults (Heine & Browning, 2014; Mudie et al., 2018). In addition to their difficulties with communication and daily activities (e.g., driving automobiles), patients with age-related dual sensory loss are likely to have poorer quality of life, anxiety, and clinical depression, and risk of developing depression (Heine & Browning, 2014; Simning et al., 2018). Older patients who have hearing loss, and who report vision impairment or with documentation of vision impairment in their medical records, are at risk for increased anxiety and decreased mental health. I suggest that you alert referring physicians to the well-established link between combined vision and hearing loss. Also, I encourage you to recommend to the patient’s primary care physician that he or she refer your patients with dual sensory loss to an optometrist and/or ophthalmologist for complete evaluation and management.  In some cases, referral to a mental health professional (psychologist or psychiatrist) would also be appropriate.

17. You’ve given me plenty of food for thought about risk factors for hearing loss, and new strategies for hearing assessment. Do you have any other words of wisdom before we wrap up this discussion?

Thanks for the reminder about food. Diet is an important determinant of health. In fact, research now clearly shows that healthy living, in general, contributes to healthy hearing, and an unhealthy lifestyle increases risk of hearing loss.

18. I don’t usually ask my patients about lifestyle, other than their occupational or recreational exposure to noise or music. What lifestyle factors are you referring to?

There is a growing literature on the effects of diet and smoking on hearing and related disorders. Recent large-scale population-based studies, as well as meta-analyses and systematic reviews, confirm the relationship between diet and hearing, and tinnitus (e.g., Spankovich et al., 2017; Tsimpida et al., 2019; Dawes et al., 2014; Dawes et al., 2020). A healthy diet consists of daily eating that includes ample fruit and vegetables, omega 3 fatty acids, polyunsaturated fats, whole grains, and lean protein, and adequate amounts of water. Persons with unhealthy diets tend to eat more processed foods, lipids and other fatty foods, carbohydrates, and refined sugars (for reviews see Spankovich et al., 2017 and Dawes et al., 2020).

19. Smoking! Everyone knows that smoking isn’t a healthy habit, but what is the specific connection to hearing?

In addition to the well-appreciated risks for cancer, smoking and nicotine-related pathophysiology includes vascular dysfunction, such as vasoconstriction, increased blood viscosity, with associated hypoxia and ischemia that adversely affect cochlear function. Smoke also contains multiple toxic substances that, in the cochlea, accumulate to produce ototoxicity (Veile et al., 2017). Nicotine even may interfere with neurotransmission and synaptic function within the neural and central auditory nervous system (Harkrider, Champlin & McFadden, 2001). The literature linking smoking with hearing loss and related disorders is substantial (Veile et al., 2017; Kumar et al., 2013; Tsimpida et al., 2019; Lin et al., 2020; Dawes et al., 2014). You mentioned noise exposure in your question. You might be interested in learning that there is a clear relationship for the added risk to hearing due to a combination of noise exposure and smoking (Li et al., 2020; Khaldari et al., 2020).

20. I would imagine that lifestyle factors are related to some of the comorbid conditions we discussed earlier. As we conclude this interesting and very practical discussion. could you comment on the connection?

Absolutely, lifestyle factors like diet and smoking are often interrelated with many comorbid conditions associated with hearing loss, including arthritis, cardiovascular disease, obesity, and a variety of other chronic health conditions (e.g., McKee Stransky & Reichard, 2018). Clearly, patients are more effectively managed when multiple caregivers coordinate efforts to manage health and hearing. Your clinical practice may also benefit from an emphasis on comorbid conditions and lifestyle factors. Most physicians will welcome information and support from audiologists as they attempt to improve their patients’ health and wellbeing. Some of the benefits you will reap include increased and varied patient referrals, increased and perhaps more diverse sources of clinical revenue, and more interesting and intellectually stimulating clinical experience, and, almost certainly, more audiologist and patient gratification and satisfaction.

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