Age-related hearing impairment and frailty in Alzheimer's disease: interconnected associations and mechanisms

Abstract

Among potentially modifiable age-related conditions linked to dementia, Alzheimer’s disease (AD),and late-life cognitive disorders, age-related hearing impairment (ARHI) or resbycusis is themost widely diffused sensory disorder and one of the principal causes of chronic disability inolder adults (Gates and Mills, 2005). The impairments of peripheral (sensory or strial) and central(predominantly neural) auditory pathways, diagnosed with different procedures, are often variouslyimbricated in determining ARHI, with mixed clinical findings (Gates and Mills, 2005). A growingbody of epidemiological evidence linking ARHI with late-life cognitive disorders (Panza et al.,2015a) suggested the potential for correcting hearing loss so that elders can function better alsofrom a cognitive point of view with appropriate treatment.ARHI is also a substantial marker for frailty in older age, another age-related clinical conditionfor identifying older persons at elevated risk for numerous adverse health outcomes such asfalls, institutionalization, hospitalization, disability, and death (Rodríguez-Mañas, 2013). Frailtyis as a multidimensional syndrome characterized by a nonspecific state of vulnerability, reducedmultisystem physiological reserve, and decreased resistance to stressors (Rodríguez-Mañas, 2013).Although there is no consensus regarding the operational definition of frailty, in general, twoare the most frequently used approaches: the first is the physical or “phenotypic” model offrailty, while the second is based on deficit accumulation, measured with the so called frailtyindexes, and defined as an accumulation of health-related deficits and disorders (Rodríguez-Mañas,2013). However, also psychological, cognitive and social factors are part of this multidimensionalsyndrome, with great influence on its definition and treatment. Cognition has already beensuggested as a possible component of frailty with increased risk of adverse outcomes. Therefore, theprevention of cognitive-related adverse outcomes including delirium (Eeles et al., 2012) and late-life cognitive disorders (Robertson et al., 2013; Panza et al., 2015b) may be possible also throughfrailty prevention.