https://orcid.org/0000-0003-2184-6139
Abstract
Dual sensory impairment (DSI), the combination of visual and hearing impairments, is associated with increased risk for age-related cognitive decline and dementia. Administering cognitive tests to individuals with sensory impairment is challenging because most cognitive measures require sufficient hearing and vision. Considering sensory limitations during cognitive test administration is necessary so that the effects of sensory and cognitive abilities on test performance can be differentiated and the validity of test results optimized.
To review empirical strategies that researchers have employed to accommodate DSI during cognitive testing of older adults.
Seven databases (MEDLINE, Embase, Web of Science, CINAHL, PsycINFO, Global Health and the Evidence-Based Medicine Reviews databases) were searched for relevant articles integrating the three concepts of cognitive evaluation, aging, and DSI. Given the inclusion criteria, this scoping review included a total of 67 papers.
Twenty-eight studies reported five categories of strategies for cognitive testing of older adult participants with DSI: the assistance of experts, the modification of standardized test scoring procedures, the use of communication strategies, environmental modifications, and the use of cognitive tests without visual and/or auditory items.
The most used strategy reported in the included studies was drawing on the assistance of team members from related fields during the administration and interpretation of cognitive screening measures. Alternative strategies were rarely employed. Future research is needed to explore the knowledge-to-practice gap between research and current clinical practice, and to develop standardized testing strategies.
Key Points
The prevalence of both sensory and cognitive impairments increases with age.
Commonly used standardized cognitive tests presume sufficient hearing and/or vision for test administration.
Individuals with sensory impairment may under-perform on cognitive tests, and proactive accommodation is essential.
Introduction
Age-related sensory and cognitive changes affect the results of behavioural tests administered in the clinical context and how individuals function in daily life [1–3]. Hearing impairment (HI) in mid-life was identified as the largest potentially modifiable risk factor for dementia, while vision impairment (VI) has been associated with greater rates of cognitive dysfunction compared to rates in age-matched healthy individuals [4–9]. Baltes and Lindenberger estimated that vision and hearing account for around 93% of the age-related variability in cognition [10]. Furthermore, hearing and vision may be predictors of cognitive function [11].
Auditory-cognitive and visual-cognitive associations are compounded when people have declines in both senses. Dual sensory impairment (DSI) is the combination of VI and HI, where one sense cannot compensate for the other. Given that both senses are significantly impaired, DSI is a complex condition in which the effects of the sensory-cognitive aging link are intensified [12–14]. Most older adults develop DSI as a result of uncorrectable age-related causes such as age-related macular degeneration and reduced auditory temporal processing [15–17]. Consequently, older adults with DSI are a highly vulnerable population at risk of further sensory as well as cognitive decline. A scoping review investigating the prevalence of DSI in population-based studies revealed a wide range of prevalence rates among adults aged 50 years and above, ranging from 1.6% to 18.2% and higher prevalence of DSI in this age group compared to younger adults [18]. Notably, sex- and gender-related differences have emerged as noteworthy factors in both hearing and vision impairments. HI is more prevalent in males aged 45–85 years old than in age-matched females, while VI is more common in females than in males [19–22].
The strength of the connections between sensory and cognitive declines may be influenced, at least in part, by methodological limitations insofar as cognitive deficits may be over-diagnosed in individuals with sensory impairment due to decreased quality of the sensory inputs when cognitive testing relies on stimuli presented during auditory and visual tasks [6]. Cognitive tests require sufficient hearing and vision for those being tested to understand the instructions and perceive the visual and/or auditory stimuli [23, 24]. However, these tests are commonly administrated in individuals living with HI and/or VI without fully considering that sensory loss may undermine the accuracy of test results. For example, the cognitive effort required by individuals with DSI during cognitive testing is potentially increased because the quality of both the auditory and visual stimuli is reduced and one sense cannot be used to compensate for the other. Such increased effort during perception likely has negative effects on cognitive test performance [25]. When HI is simulated in cognitively healthy adults, test scores on auditory-based cognitive tests (e.g. memory tests) decrease significantly compared to performance in standard conditions [26]. Performance on cognitive tasks that require vision (e.g. the Stroop colour word test) is also significantly reduced in older individuals when visual disorders such as cataracts and decreased colour perception are simulated [27, 28]. Furthermore, VI and HI have each been associated with poorer outcomes on cognitive assessments as illustrated by lower scores on cognitive screening tests that include multiple cognitive domains (e.g. Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA)) [29, 30].
There are currently no evidence-based clinical guidelines for administering existing cognitive tests to older adults with both VI and HI and there are no standardized and validated specialized cognitive tools to test those with DSI. To our knowledge, the literature reports a few cognitive evaluation tools designed for individuals living with DSI who rely on the tactile modality [31–34]. However, these tools have not been integrated into clinical practice and have not yet been validated. The purpose of this scoping review was to explore accommodations for sensory impairment used in research during the cognitive evaluation of older adults with DSI.
Methods
Given the exploratory nature of this study, a scoping review was the preferred methodological approach. We adhered to the Joanna Briggs Institute methodology for scoping reviews [35]. The protocol was developed using the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA-P) statement and reporting of this review was done using the PRISMA Extension for Scoping Reviews (PRISMA-ScR) [36, 37].
Eligibility criteria
Studies focusing on older adults with DSI were eligible for inclusion because of that population’s increased risk of cognitive decline [38]. Participants in eligible studies had to have both HI and VI as identified using behavioural tests or self-reports, regardless of the nature and aetiology of their sensory losses. Participants were not required to be diagnosed with, or have suspected cognitive decline, as this review addressed measures used to evaluate cognitive performance. Studies that did not focus on cognitive measures and related strategies were excluded. Any study considering cognitive measures in older adults with any sensory impairment was included in the early stages of the scoping review, but at the stage of full-text review, the inclusion criteria were narrowed to only include studies including participants with DSI, who were at least 65 years old. The final study eligibility criteria are outlined in Table 1.
Scoping review inclusion and exclusion criteria
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Scoping review inclusion and exclusion criteria
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Information sources
Six databases (MEDLINE, Embase, Web of Science, CINAHL, PsycINFO, and Global Health) were searched for articles in accordance with PRISMA. Furthermore, all eight databases from the Evidence-Based Medicine Reviews database were searched.
Search
The concepts and database search strategies were developed with the collaboration and expertise of an experienced librarian at the Université de Montréal’s School of Optometry. Search terms and keywords were explored through initial searches in the PubMed database. Relevant keywords were searched for synonyms, broader and narrower terms, as well as alternate spellings and were adapted for searches in the different selected databases.
Three main concepts were explored: (A) cognitive evaluation; (B) DSI; and (C) older adults. Cognitive evaluation refers to any measure or tool to evaluate cognitive domains (e.g. memory, language, abstraction, executive function, attention) either for cognitive screening or neuropsychological assessment. DSI was defined as a condition that combines both HI and VI [12]. Impairments could be defined using self-report, questionnaires, or behavioural measures (e.g. tests of visual acuity, contrast sensitivity, pure-tone, or speech-in-noise thresholds). Older adults were defined as individuals 65 years of age or older. No studies were excluded based on the sex and gender of their participants, their spoken languages, communication preferences, or comorbid health conditions.
Selection of sources of evidence
This review explored peer-reviewed studies that adapted cognitive tools or evaluated adapted tools, their administration, their scoring or their interpretation to accommodate the comprehension of test instructions or the perception of test stimuli by older individuals with DSI. Selected studies included any research design providing empirical data that were collected in any setting. Searches were not limited in publication time or location but were limited to publications in the French, English, Portuguese and German languages. Editorials, commentaries, conference publications, theses and dissertations, books or letters were excluded. Searches were performed in May 2022. An example of the search strategy performed in the MEDLINE database is provided in Appendix A.
The articles resulting from database searches were exported to the EndNote X9 software (Clarivate Analytics, PA, USA) and subsequently to the Covidence software (Veritas Health Innovation, Melbourne, Australia) where article duplicates were removed [39, 40]. Within Covidence, each title, abstract and full article was reviewed by two independent reviewers using the criteria presented in Table 1. Any conflict in decisions was reviewed and resolved by a senior reviewer.
Data charting and synthesis of results
Articles that met the inclusion criteria had their data extracted into a Microsoft Excel pre-designed spreadsheet. Data were synthesized in a table and included qualitative and quantitative information such as study design and setting, sample characteristics such as sex/gender and age, type of vision and hearing assessments, cognitive tests used by researchers/professionals, administration strategies and psychometric test properties (if reported), as well as study results and main points.
Results
Selection of evidence sources
The database searches yielded 1,169 publications. After removing duplicates, the titles and abstracts of 791 articles were screened and 281 studies were deemed eligible to be reviewed comprehensively. At the stage of full-text review, 213 studies were excluded for reasons such as the absence of cognitive evaluation, or sample population characteristics. A final total of 67 papers exploring the cognitive evaluation of older adults living with actual, non-simulated DSI were included (see PRISMA flow chart in Figure 1).
PRISMA Flow Diagram.
Characteristics of evidence sources
Study information
Included studies dated back to 1998, up to May 2022. Of the 61 studies that reported their setting, 12 were conducted in long-term care homes, ten were conducted in clinics or hospitals and one in a research laboratory, while others were conducted in various community settings. Most articles utilized a cross-sectional design (n = 37) while 30 were longitudinal studies.
Study participants’ characteristics
In 42 studies, the age range of the participants was not specified. In 19 studies, participants were from different age categories, including young-old individuals (aged 65–74 years), middle-old individuals (aged 75–84 years), and old-old individuals (over 85 years). An additional five studies primarily recruited young-old and middle-old participants, while only one study specifically focused on middle-old and old-old individuals. Among the reviewed studies, 53 used terminologies interchanging sex and gender; 12 studies exclusively referred to the sex of their participants, utilizing terms such as male and female; two studies referred to the gender of participants. Fifty studies provided the ratio of the sex and/or gender of their overall participant sample. In those, 25 studies had an equal distribution of both sexes/genders; the 25 other studies had a biased representation of females/women with one study exclusively including females/women as participants. For studies that only presented data on sensory subgroups of their sample (n = 12), nine studies indicated a balanced distribution of males and females among individuals with DSI; two studies displayed a bias toward males; one study exhibited a bias toward females. Notably, five studies did not provide any data pertaining to the sex or gender distribution within the DSI subgroup.
Sensory measures
All but two studies performed vision and hearing tests to identify sensory loss as part of their research protocols. However, Appendix B illustrates significant variability in the methods used to ascertain sensory loss, highlighting the lack of a standardized assessment method for sensory impairment prior to cognitive evaluations. In 30 studies, behavioural vision tests (e.g. the Snellen chart, the Early Treatment Diabetic Retinopathy Study) were used, 28 studies used self-report screening tools of visual function; seven studies included both self-report and behavioural measures of vision. As for measures of hearing, 24 studies employed behavioural measures (e.g. pure-tone audiometry); 33 studies used self-report measures; eight studies used both self-report and behavioural tests.
Cognitive measures
A total of 23 different cognitive tools were reported across the included studies, 19 screening tools and 4 diagnostic tools. The MMSE was the most commonly used (n = 27) [41]. Thirteen studies evaluated specific cognitive domains with the use of cognitive subtests; for example, the Digit Span Backwards subtest the revised Wechsler Adult Intelligence Scale WAIS–R was used to measure working memory and animal naming to measure verbal fluency [42]. The Cognitive Performance Scale (CPS) was used in 11 studies [43]. Four studies used the Telephone Interview for Cognitive Status (TICS) [44]. Dementia diagnosis was reported in four studies. The MoCA [45] and the Clinical Dementia Rating [46] were each used by three studies. Other reported measures included neuropsychological test batteries to establish the presence or absence of dementia (n = 2), and self-reported perception of cognitive function (n = 2).
Only one of the studies used a measure that accommodated for DSI. This cognitive tool consisted of a tactile test battery that did not require participants to have vision or hearing [31]. In this study, task instructions were provided by trained consultants using tactile sign language, spoken language, by use of written texts or other means adapted to the participants’ communication requirements. The cognitive tasks included tactile versions of a spatial memory test, a clock reading test, a tactile form board test and naming tests. Seven studies used tests that inherently accommodate for visual impairment. These included cognitive evaluations conducted over the phone, without the presentation of visual items, or tests where the visually presented items were not completed by participants and the scoring was modified accordingly [31, 44, 47]. However, none of the studies used a test that inherently accommodated for hearing impairment, such as by using tests that are vision-based only or pocket-talkers [48–50].
Strategies employed during the administration of cognitive tests
All identified cognitive evaluation tools and strategies to administer cognitive tests are provided in Appendix B. Of the 67 included articles (full bibliography available in Appendix C), only 28 studies made use of strategies during the administration or the interpretation of a cognitive measure. Five categories of strategies were identified: (A) the assistance of experts (18 studies) (B) the modification of standardized tests’ scoring procedures (four studies), (C) the use of adaptive communication strategies (four studies) (D) environmental modifications (two studies) and (E) the use of cognitive tests without visual and/or auditory items (six studies). Details of these strategies are included in Appendix B.
Six studies employed cognitive tests that, by design, did not include visual items, such as the Telephone Interview for Cognitive Status (TICS), and/or auditory items such as tactile tests [13, 31, 44, 51–53]. Another reported strategy was the modification of established standardized tests’ scoring procedures. For instance, the MoCA and the MMSE in their blind versions [29, 54–56] were respectively administered in two articles. In these studies, test total scores were modified by not counting the points awarded for visually presented items. Communication strategies (e.g. use of assistive devices, adapted speech and requesting feedback during the conversation) were also employed to accommodate individuals with DSI in four studies [31, 51, 57, 58]. Only two studies ensured a quiet environment to optimize speech perception [51, 58].
Strategies for the interpretation of cognitive tests:
In 19 studies [3, 31, 58–72], testing was conducted with the assistance of team members (e.g. research assistants, nurses and/or social workers) trained on various aspects of sensory and cognitive aging. In some studies, deafblind/DSI specialists, trained research assistants or nurses administered tests to individuals with DSI and served as consultants during the sessions. In other studies, clinical psychologists, geriatricians, and geriatric psychiatrists were actively involved in the consensus process to develop the clinical profile of the study participants. Although these professionals did not directly accommodate for sensory impairment, they were able to use specialist knowledge to assist the research team in contextualizing the sensory impairment when interpreting cognitive test scores [59, 63, 65].
Psychometric properties
None of the 28 studies that accommodated cognitive test administration for older adults with DSI conducted validity analyses to ensure that their strategies did not alter the way in which the cognitive tools measure cognitive function. One article established the consistency of the cognitive measure they used across test administrators by reporting an inter-rater reliability of 90%, demonstrating very good agreement across test administrators [66]. Sensitivity and specificity can be determined through comprehensive statistical analyses, as demonstrated in the adaptation of the Montreal Cognitive Assessment (MoCA) for individuals with visual impairment [47]. Alternatively, these metrics can be derived from comparative assessments, as highlighted in the study by Utoomprurkporn et al. (2021) [73] which involved evaluating a cognitive tool tailored for hearing loss among older individuals with diverse levels of cognitive function and hearing impairment.
Discussion
The present review aimed to identify the strategies used during the cognitive evaluation of older adults with DSI. Notably, we discovered a lack of such accommodations and consideration of the sensory profile of participants. Most studies that did assess vision and hearing used self-report measures. However, combining self-report with behavioural tests should give a more complete assessment of the sensory abilities of older adults [74]. Cognitive evaluation without behavioural sensory assessments is highly problematic because cognitive scores may be lower due to sensory limitations that are not revealed using self-report measures and that the tester is not aware of [6]. There are currently no validation studies of appropriate cognitive measures for people with DSI. There is a need to develop tools so that the cognitive abilities of older individuals living with DSI can be assessed independent of sensory limitations.
Effect of clinical setting on cognitive evaluation
The included studies demonstrate a paucity of solutions across the five identified categories. The majority of studies that adapted their protocol were conducted in long-term care homes, an environment with a high prevalence of residents with combined sensory and cognitive impairments [3]. In this environment, it is especially important to accommodate sensory impairments when testing cognition. Considering sensory impairments when interpreting cognitive test scores will provide more accurate assessments that may contribute to better person-centered approaches to care. Cognitive evaluations encompass both screening for the purpose of referral, and assessment for diagnostic purposes. The researchers working in long-term care homes tended to use the assistance of trained experts to conduct and interpret cognitive testing in older adults with DSI. This approach likely increases how informative assessments are because the expertise of specialists can substantiate the interpretation of tests results and provide person-centered context. However, depending on the institutional setting, such experts may not be involved in screening and there may be delays in referral for assessments. Until tests validated for use with people living with DSI are developed, better inter-professional collaboration and training in how to accommodate sensory impairment during testing could reduce delays and reliance on costly and time-consuming resources. Client-centered strategies such as the provision of visual and/or hearing aids as well as other assistive technologies and strategies could benefit those with DSI who are at risk for, or living with cognitive decline.
Challenges in standardized testing for concurrent vision and hearing impairment
Very few articles included in this review employed communication strategies or environmental modifications for people with DSI. Only four studies used standardized cognitive tests where the visually presented items were removed, and the scoring was adjusted accordingly. The MoCA-Blind, without visually presented items, has been validated against its full version with the visually presented items. Specifically, withdrawing the visual items from the test and adjusting scoring generated excellent test specificity (98%) and adequate sensitivity (63%) in individuals with mild cognitive impairment, with the caveat that this approach omits screening of some cognitive functions when visual test items are removed [47]. The blind version of the MMSE uses age-dependent cut-off values, has been validated, and reports excellent sensitivity (91–100%) and specificity (80–100%) [75]. Such assessments do not require clients to visually perceive test items and can be administered over the phone. The obstacle with these measures is that they still do not accommodate for hearing impairment, especially when such measures are administered remotely. A version of the MoCA that is presented visually (no hearing required) has been explored but yielded less sensitivity than the MoCA-Blind [24].
Researchers often make statistical choices to manage population-based data that include individuals with sensory impairment. For example, in this scoping review, we identified a study that managed the effect of sensory impairment on cognitive outcomes by analysing the data with and without participants who had mild cognitive impairment or severe cognitive dysfunction. The authors made this choice because they were unsure if severe cognitive impairment would interfere with the participants’ ability to follow the instructions required to complete the vision and hearing measures [68, 70]. However, it would be better to test for, and accommodate, sensory impairments in advance of cognitive testing. The tactile test battery proposed by Bruhn and Dammeyer is an innovative step toward the validation of a measure for older adults living with DSI [31]. The psychometric properties of such adapted cognitive measures will need to be revisited for administration in older adults with DSI. Unfortunately, only one article reported reliability data, and none provided validity data. An interprofessional team will likely need to collaborate on developing and validating appropriate cognitive tests for people living with DSI, including experts in neuropsychology and sensory impairment. However, there is a potential risk that these adapted tools will be considered more cumbersome as they may require additional testing material, training, and time for practitioners.
Limitations
DSI only recently started receiving increased scientific attention given the increase in its prevalence [76]. It may be too early to expect progress in research or clinical practice to develop and implement novel strategies given that rigorous standardization and validation is a lengthy process. It is likely that existing adaptive strategies specific to the administration of cognitive tests in individuals with single sensory impairment have been missed because our review focused on DSI. Ignoring such strategies prevents cross-comparisons with those that may be suitable with clients living with DSI. Furthermore, it would be relevant to explore the effect of degree of sensory impairment, as well as the effectiveness of using assistive technologies and environmental modifications for individuals with sensory impairments of all ages to compare across age groups.
Future studies should also explore how sex- and gender-related differences may influence sensory-cognitive links, best practices for accommodating sensory loss during cognitive testing, and for subsequent care planning. More generally, future studies should include participants with a diverse range of characteristics, including but not limited to race, education, communication modalities, language, and the presence of comorbidities. By actively addressing these factors, researchers can foster a more representative and comprehensive understanding of various populations, thereby promoting the validity and applicability of study findings.
Failure to optimize cognitive testing for individuals with sensory impairment may lead to negative consequences, such as the misinterpretation of results due to a lack of consideration of their sensory context [76, 77]. There is a risk of reduced test integrity by modifying the scoring techniques, the individual test items or the use of non-standardized methods of administration [24, 76]. Misinterpretations of cognitive evaluations may have serious consequences for research and care for older adults with DSI.
Acknowledgements:
The authors acknowledge Patrice Dupont, librarian at the School of Optometry at the University of Montreal, for his valuable help and guidance in developing the search strategy for this scoping review. We also thank the constructive and productive assistance of Gabrielle Aubin, Breanna Jaipaul, Shreya Budhiraja, Kayleigh Gauvin, Peter Holzhey, Atul Jaiswal, Abinethaa Paramasivam and Sangeetha Santhakumaran and the Canadian Consortium on Neurodegeneration in Aging (CCNA) team 17 members Alison Chasteen, Paul Mick, Jennifer Campos, JB Orange who cooperated in the conception and completion of this study.
Declaration of Conflicts of Interest:
None.
Declaration of Sources of Funding:
This research was supported by an infrastructure and operating grant to the CCNA from the Canadian Institutes of Health Research (Grant no. CNA-163902). This grant supports the COMPASS-ND study and the work of CCNA Team 17 principal investigators (DG, NP, MKPF, MS & WW). The CCNA study received local approval from the participating centres’ research ethics committee or institutional review board. Dumassais is supported by a Canadian Institutes of Health Research Canada Graduate Scholarships for her master’s studies. Wittich is supported by a Junior 2 chercheur boursier career grant, provided by the Fonds de recherche du Québec—Santé (#281454).
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