Abstract
PurposeThis study examined the central auditory processing (CAP) assessment results of adults between 45 and 85 years of age with probable pre-clinical Alzheimer’s disease – i.e., individuals with subjective memory complaints (SMCs) as compared to those who were not reporting significant levels of memory complaints (non-SMCs). It was hypothesized that the SMC group would perform significantly poorer on tests of central auditory skills compared to participants with non-SMCs (control group).MethodsA total of 95 participants were recruited from the larger Western Australia Memory Study and were classified as SMCs (N = 61; 20 males and 41 females, mean age 71.47 ±7.18 years) and non-SMCs (N = 34; 10 males, 24 females, mean age 68.85 ±7.69 years). All participants completed a peripheral hearing assessment, a CAP assessment battery including Dichotic Digits, Duration Pattern Test, Dichotic Sentence Identification, Synthetic Sentence Identification with Ipsilateral Competing Message (SSI-ICM) and the Quick-Speech-in-Noise, and a cognitive screening assessment.ResultsThe SMCs group performed significantly poorer than the control group on SSI-ICM −10 and −20 dB signal-to-noise conditions. No significant differences were found between the two groups on the peripheral hearing threshold measurements and other CAP assessments.ConclusionsThe results suggest that individuals with SMCs perform poorly on specific CAP assessments in comparison to the controls. The poor CAP in SMC individuals may result in a higher cost to their finite pool of cognitive resources. The CAP results provide yet another biomarker that supports the hypothesis that SMCs may be a primary indication of neuropathological changes in the brain. Longitudinal follow up of individuals with SMCs, and decreased CAP abilities should inform whether this group is at higher risk of developing dementia as compared to non-SMCs and those SMC individuals without CAP difficulties.
Highlights
With over 47 million individuals living with dementia worldwide in 2015, this syndrome is considered a growing global epidemic in older adults (Prince et al, 2015)
Of the 95 participants who were selected for the study, 61 participants (20 males and 41 females, mean age 71.47 ±7.18 years) had Memory Assessment Clinics Questionnaire (MAC-Q) scores ≥25, categorized as subjective memory complaints (SMCs)
CAPS test protocols suggest assessing each ear separately and the scores were calculated for each ear as well
Summary
With over 47 million individuals living with dementia worldwide in 2015, this syndrome is considered a growing global epidemic in older adults (Prince et al, 2015). Alzheimer’s disease (AD) is the most common cause of dementia in older adults accounting for 60– 80% of all-cause dementia (Lambert et al, 2014). The National Institute of Aging-Alzheimer’s Association Work Groups on diagnostic guidelines suggest that the course of AD can be divided into three subsequent stages: (1) the pre-clinical stage of AD (no impairment in cognition on standard assessments and biomarker evidence for AD), (2) mild cognitive impairment (MCI) due to AD (impairment on memory or other domains of cognition on a standard assessment and biomarker evidence for AD), and (3) dementia due to AD (dementia and biomarker evidence for AD plus subtle cognitive decline) (Jack et al, 2011; McKhann et al, 2011; Sperling et al, 2011; Albert et al, 2013). Current evidence suggests that the self-reported decline in memory or other cognitive functions in the presence of normal performance on neuropsychological measures is associated with an increased risk for future cognitive decline and AD dementia (Glodzik-Sobanska et al, 2007; Wang et al, 2011; Scheef et al, 2012)
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