Editor's Note: This is part one of a two-part article that focuses on the state of evidence on cognitive decline and hearing loss. Part two, to be published in the November 2017 issue, will discuss research evidence of hearing loss treatment in delaying the onset and reducing the negative health outcomes of dementia.
As life expectancy increases, so does the number of chronic conditions that older people live with, including age-related hearing loss and dementia (Lancet. 2012; 380:2144 http://bit.ly/2ukID3j). The number of people with hearing loss in the United States is projected to almost double by 2060, outpacing the overall population growth rate (JAMA Otolaryngol Head Neck Surg. 2017;143:733 http://bit.ly/2oqxIzB; Am J Public Health. 2016;106:1820 http://bit.ly/2enGNoy). Similarly, the global prevalence of Alzheimer's disease is estimated to double every 20 years and affect 65.7 million people by 2030. Age-related hearing loss and dementia have a marked impact on a person's social functioning, independence, and quality of life, resulting in medical consequences that significantly affect society (Alzheimers Dement. 2011;7:61 http://bit.ly/2w6th1g; Geriatric Mental Health Care. 2013;1:29 http://bit.ly/2uWlAMC).
EVIDENCE FROM REPORTS
Core behaviors associated with dementia include deterioration in memory, reasoning, communication, social abilities, and daily functioning (Alzheimers Dement. 2011;7:280 http://bit.ly/2uW61EB). Since there is no cure for dementia or Alzheimer's (the most common cause of dementia), scientists are continually trying to identify modifiable risk factors and interventions to prevent disease onset, slow down its progression, and minimize threats to safety and quality of life.
To this end, the National Academies of Sciences, Engineering, and Medicine (NASEM) recently sponsored a workshop and published the report, “Preventing Cognitive Decline and Dementia: A Way Forward,” which listed seven potentially modifiable risk factors: diabetes, midlife hypertension, midlife obesity, insufficient physical activity, depression, smoking, and low educational attainment (NASEM, 2017 http://bit.ly/2upy27p). The report cited that a 10 percent reduction in each of these risk factors could dramatically reduce the prevalence of Alzheimer's, which underscores the importance of learning more about promising interventions to prevent cognitive decline and dementia.
Three of the interventions posited may prevent cognitive decline or dementia: blood pressure management for people with hypertension, cognitive training (CT), and increasing physical activity levels. The latter two are notably relevant to audiologists. A fourth intervention, promoting social engagement independent of cognitive training, was mentioned but not included in the review (IOM, 2015 http://bit.ly/2vBiA6H).
Cognitive training denotes a broad set of interventions aimed at enhancing reasoning, memory, and processing speed through training exercises (e.g., learning a new language) or daily activities to improve proficiency (e.g., playing bridge; NASEM, 2017 http://bit.ly/2upy27p). The review concluded that the evidence of CT efficacy, while encouraging, was inconclusive and needed further research. Notably, many of the studies reviewed had intervention arms that included individual and group training sessions, social interactions, and memory trainings that all required adequate hearing and speech processing to complete. However, these studies rarely considered hearing status as a criterion in their subject selection.
Optimizing physical activity as an intervention involves engaging in activities like aerobics, yoga, etc. The review comprehensively discussed the Lifestyle Interventions and Independence for Elders (LIFE) study, a multicenter, randomized, controlled trial that included 70- to 89-year-olds who had a sedentary lifestyle and a high risk for mobility disability (JAMA. 2014;311:2387 http://bit.ly/2vBgKTl). The intervention arm included home-based activities and health education workshops. Notably, hearing status was part of the subject selection criteria despite the fact that moderate or greater hearing loss is associated with reduced physical activity levels (self-reported and objectively measured), sedentary behavior, perceived mobility disability, and difficulties performing daily activities (J Am Geriatr Soc. 2014;62:1427 http://bit.ly/2w6rNUO; Prev Med. 2013;57:143 http://bit.ly/2w6tRfy; J Am Geriatr Soc. 2015;63:1164 http://bit.ly/2w6c08x). Based on the systematic review, the authors concluded that while the data are compelling, there is insufficient evidence to conclude that increased physical activities can slow down, prevent, or delay the onset of cognitive decline.
Finally, the Institute of Medicine (IOM), in a separate report on mitigating the effects of cognitive aging, noted the potential benefits of social engagement (IOM, 2015 http://bit.ly/2vBiA6H). The IOM recommended that schools and professional societies develop and disseminate core competencies, curricula, and continuing education opportunities that focus on addressing cognitive health and aging. The report also suggested that health care professionals use patient visits to identify risk factors and strategies to minimize the risk of cognitive decline.
EVIDENCE FOR HEARING INTERVENTIONS
The NASEM and IOM reports illustrated the impact of cognitive aging on the fabric of society, and more importantly, urged stakeholders to help older adults live safer and fuller lives as they age. Considerable effort is being placed on identifying interventions that could delay the onset of dementia, thereby reducing its global prevalence (Alzheimers Dement. 2016;12:459 http://bit.ly/2w6rrgK; Arch Gen Psychiatry. 2011;68:617 http://bit.ly/2w6jdVW). Per the cascade hypothesis, it is likely that hearing loss directly affects cognition via impoverished sensory input and indirectly through a decrease in socialization. By restoring hearing and optimizing communication, it follows that interventions directed at optimizing communication and social engagement could lessen the probability of hearing loss to “cascade” into cognitive decline (Aging Ment Health. 2014;18:671 http://bit.ly/2uq48jg). Considering that dementia affects 25 to 30 percent of people over 85 years old and that more than 90 percent of dementia patients have hearing problems, it is clear there is a lot of work to be done.
Underscoring this evidence-based view is that (1) hearing loss may be a forerunner of cognitive decline, making older adults with cognitive impairment candidates for available auditory enhancements; and that (2) certain behaviors (e.g., social engagement) may offer some protection against cognitive decline, suggesting interventions to optimize communication and reduce social isolation.
To kick off a roadmap to manage patients with dementia, hearing health professionals must first communicate with physicians in primary care and geriatric medicine about hearing loss as an early marker and potentially modifiable risk factor of dementia. Physical examination and diagnostic testing should include a hearing evaluation. In fact, hearing loss or rapid decline in hearing should be underscored as a precursor of cognitive decline or a useful marker for dementia diagnosis (J Gerontol A Biol Sci Med Sci. 2012;67:997 http://bit.ly/2w6lgJN). Therefore, identifying patients who are at risk of hearing loss can also serve as a preventive screen to avoid cognitive impairment (Otol Neurotol. 2014;35:775 http://bit.ly/2w5UMbp; Audiol Neurootol. 2014;19 Suppl 1:2 http://bit.ly/2w6zgD4). A timely auditory assessment and rehabilitation may yield considerable benefits for patients and their families. Physicians must also be informed that hearing impairment may confound results of cognitive tests. Hearing enhancements, such as a Pocket Talker, can be used during physician visits to help reduce a patient's listening effort and facilitate reallocation of processing resources.
Second, as hearing loss is known to cause social isolation and reduce intellectual and cultural stimulation, hearing health professionals should inform physicians of the value of hearing enhancements in optimizing communication and ensuring engagement, which are critical to a patient's quality of life and healthy aging. Early treatment of hearing impairment must be viewed as a vehicle for maintaining social participation, potentially reducing the burden associated with dementia and other co-morbidities (PLoS One. 2016;11:e0156876 http://bit.ly/2w6DNp5).
Third, audiologists must recognize the presence of impaired cognitive function when managing and assessing the hearing performance of patients with cognitive decline. These patients respond to what and how we speak to them, so patience is critical. Speak clearly using simple words, maintain eye contact, repeat instructions, and provide sufficient reinforcement to help patients remember.
Finally, audiologists must help patients learn and practice home safety measures that accommodate their hearing issues. The primary treatment goals for patients with dementia include maximizing independent function and reducing caregiver burden. Inform patients of the benefits of notification appliances (e.g., smoke alarms, carbon monoxide detectors) that produce low-frequency sounds, visual signals (e.g., strobe lights), or vibrotactile signals (e.g., shake the bed or pillow). Safety checklists stress the importance of having functional smoke detectors and carbon monoxide alarms but may not mention that the presence of hearing loss may interfere with audibility. The patient's family must also be informed about useful technology such as phones with voice amplification and visual ringers.
Hearing loss and dementia are important public health concerns with critical social and economic costs. Recognizing research evidence and multidisciplinary interventions may be key to optimizing patient outcomes.