Prevalence of Individuals With Deafblindness and Age-Related Dual-Sensory Loss

Abstract

Introduction

The authors of this paper have compiled a report on the prevalence of deafblindness and dual-sensory loss based on the review of existing estimates. The purpose is to inform readers of the importance of using consistent, well-researched definitions and survey questions in future prevalence studies.

Methods

Articles were extracted through ProQuest and EBSCOhost, online library databases of Cambrian College and Laurentian University. Keywords search included “deafblindness,” “dual-sensory impairment,” “dual-sensory loss,” “age-related,” “congenital,” “acquired,” and “prevalence.” Additionally, the authors conducted a search with Google for research reports and Google Scholar for other relevant peer-reviewed articles.

Results

This review provides a current overview of prevalence estimates of deafblindness and age-related dual-sensory loss around the world, examining 19 articles or reports published over the last 20 years (2000–2020) in 18 countries, including the European Union (consisting of 8 countries). In line with the prevalence estimates by the World Federation for the Deafblind global report 2018, the review indicates an estimated 0.2–2% prevalence of dual-sensory impairment and underscores varying ranges of prevalence among populations, studies or countries, age groups, and types of deafblindness. The review highlights that the prevalence of deafblindness or dual-sensory loss was often not comparable across studies, but it is clear that the prevalence of dual-sensory impairment increases with age. The studies varied in methods (e.g., population surveys, cross-sectional, and longitudinal studies).

Implication for Practitioners

The review provides evidence of varying ranges of prevalence rates. Future prevalence studies may benefit from consistent definitions, standard data-collection tools to do better comparisons across countries, and identify factors that predict higher or lower prevalence rates among populations and age groups.

Keywords

deafblindness dual-sensory loss age-related congenital acquired prevalence dual-sensory impairment

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Deafblindness involves varying combinations of visual and hearing impairment to such an extent that neither the vision nor hearing can be employed as a means of accessing information, communication, and participation in society (Deafblind International, 1999). Deafblindness, also known as dual-sensory impairment, can be classified into three categories: (1) congenital, (2) acquired, and (3) age-related dual-sensory loss (Dammeyer, 2014; 2015; Jaiswal, Aldersey, Wittich, Mirza, & Finlayson, 2018; Simcock, 2017; Wittich, Southall, Sikora, Watanabe, & Gagné, 2013). Deafblindness is a distinct disability and poses unique challenges because individuals with dual-sensory impairments may not be able to compensate for the loss of one sense with the other (Dammeyer, 2014; Saunders & Echt, 2007; Wittich, Jarry, Groulx, Southall, & Gagné, 2016). Yet, The World Federation of the Deafblind (WFDB, 2018) global report confirms that the number of individuals with deafblindness is often underestimated, and these individuals face inequalities with respect to human rights protected in the United Nations Convention on Rights of Persons with Disabilities 2008.

Evidence suggests that the prevalence of dual-sensory impairment is expected to increase with age (Dammeyer, 2015; Schneider et al., 2011; Swenor, Ramulu, Willis, Friedman, & Lin, 2013; WFDB, 2018; Wittich et al., 2013; 2016). Often, government surveys, such as the Canadian Survey on Disability (CSD), gather seeing and hearing prevalence data as a single sensory disability. The insufficient or inconsistent data on deafblindness, as a single disability, and for all age groups, makes it difficult when advocating for funding and programming at the policy level (Schneider et al., 2012; Simcock, 2016). The authors of this paper have compiled a report on the prevalence of deafblindness and dual-sensory loss based on the review of existing estimates. The purpose is to inform readers of the importance of using a consistent, well-researched definition and survey questions in future prevalence studies.

Methods

The authors conducted a review of published literature in December 2016 and updated it in June 2020. Articles were extracted through ProQuest and EBSCOhost, online library databases of Cambrian College and Laurentian University. Keyword searches included variations of the terms “deafblindness,” “dual-sensory impairment,” “dual-sensory loss,” “age-related,” “congenital,” “acquired,” and “prevalence.” Additionally, the authors conducted a search with Google for research reports and Google Scholar for other relevant peer-reviewed articles. Finally, the sources were systematically screened for information related to prevalence estimates. The prevalence rate is based on total cases, which include both new and pre-existing cases accounted for at a specified time (Centers for Disease Control and Prevention, 2012).

Results

This review provides a current overview of prevalence estimates of deafblindness and age-related dual-sensory loss around the world after examining 19 articles/reports published over the last 20 years (2000–2020). Based on the review of 19 articles/reports, authors report on available prevalence estimates in 18 countries/European Union (8 countries) tabulated in Table 1. The authors used the terms “DSL” (i.e., “dual-sensory loss”) for older adults (65 years and above) and “deafblindness” for those with both congenital and acquired conditions in other age groups.

Table 1.

Prevalence Data of Deafblindness, Dual-Sensory Impairment or Loss (DSI, DSL).

S. No.	Country or region	Age group, prevalence in %	Methods used or agency	Measurement of deafblindness, DSI, DSL	Source
1	Australia	Baseline = 6 55–60 years = 0 >80 years = 26.8	2015 Blue Mountains Hearing Study participants aged ≥55 years, examined between 1997 and 1999 (baseline) and 2002 and 2004.	Hearing thresholds were measured with the use of pure-tone audiometry. Visual acuity was measured with a logMAR chart while the subject wore distance glasses, if they owned a pair. DSI was defined as combined presenting visual acuity (better eye) <20/40, and PTA 0.5–4 kHz (better ear) >25 dB HL. Incidence of DSI was considered by the use of two at-risk subpopulations: (i) participants with no sensory impairment and (ii) with one type of sensory impairment at baseline.	Schneider et al. (2012)
		0.5 of resident population. Of 0.5, 67% were 75 years and older	2009 Survey of Disability, Ageing and Carers compared to general population and Disability Services National Minimum Dataset (DS NMDS).	Those individuals reporting a disability due to loss of sight (not corrected by glasses or contact lenses) and loss of hearing where communication is restricted, or an aid to assist with, or those individuals reporting a disability due to loss of sight (not corrected by glasses or contact lenses) and loss of hearing where communication is restricted, or an aid to assist with, or substitute for, hearing is used. • The DS NMDS describes deafblindness as not just vision impairment with a hearing loss, or a hearing loss with visual impairment, but rather as a unique disability of its own requiring distinct communication and teaching practices.	Dyke (2013)
2	Belgium	>65 = 33.9 (LTCF) >65 = 24.6 (HC)	InterRAI database for HC/LTCF across Belgium on 8 out of 10 cities. Numbers differ year over year.	The two interRAI assessment instruments (HC & LTCF) used contain approx. 3,000 items capturing multiple domain areas, with considerable overlap. Presence of DSI was determined using the Deafblind Severity Index.	Guthrie et al. (2016)
3	Brazil	5–17 years = 0.060	XII Recenseamento Geral do Brasil Censo Demografico 2010 Sample size 9,693,058	Washington Group Questions for sight and hearing. Deafblindness considered “a lot” of difficulty in both domains	WFDB Global Report 2018 Annex 2
		18–39 years= 0.080
		40–59 years = 0.310
		60–74 years = 1.040
		75+ years = 4.570
4	Canada	45–85 years = 6.4 males and 6.1 females70–75 years = 2580–85 years = 40	An analysis of the Canadian Longitudinal Study data on Aging from the first wave on Aging. Prevalence proportions for 2012–2015 and counts for 2011 and 2016 were estimated. Among Canadians aged 45–85 years, 570,000 males and 450,000 females had DSL.	Audiometry and visual acuity were measured	Mick et al. (2020)
		>65 years = 25.8 (LTC)	InterRAI assessment data from LTCF/HC Ontario, Canada. In Ontario, the sample size was approx. 339,000 in LTCF and 250,000 in home care	Presence of DSI was determined using the Deafblind Severity Index. It includes two items, one each on functional hearing and vision. Trained assessors completed assessments in Ontario using standardized terminology of InterRAI manuals from all sources including the person, their informal care givers, other health providers (e.g., primary care physician) and clinical records, as available and appropriate.	Guthrie et al. (2016)
		Home care > 65 years = 14.5 (HC)
		<18 years = 5.7 >65 years = 69 >85 = 43.1	Client Chart review from 3 rehabilitation agencies in the Montreal region, with sample size of 564. Overall prevalence estimate of 15/100,000	Data on visual acuity, visual field, hearing detection thresholds, and demographic variables	Wittich et al. (2012)
		15 years and over = 1.67	2017 Canadian Survey on Disability data by Employment & Social Development Canada National survey of 50,000 Canadians aged 15 and over who reported having a long-term condition or difficulty on the Activities of Daily Living question from the 2016 Census long-form questionnaire	Disability Screening Questions established subjective assessment of disability and the severity classes at mild, moderate, severe, and very severe	Jaiswal (2019)
		25 to 64 years = 1.14
		65 to 74 years = 3.26
		75 years and over = 6.96
5	Denmark	Children = 0.53 Adults = 0.29 Both children and adults = 0.34	Denmark National Survey study in 2000 on the population. 190 congenitally deafblind people—Children 1:19,000; Adults 1:34,000; and both combined 1:29,000. Note: prevalence converted from ratio to percentage.	(1) Medical screening and tests of hearing and vision. (2) Functional evaluation of vision, hearing, and use of tactile modality including evaluation of the senses in social interaction and communication.	Dammeyer (2010)
	Europe, 27 states/region	Overall= 0.48 >64 years = 0.2 >65 years = 2	Survey of 27 states/regions in Europe from September 2012 to September 2014	Survey regarding the rights and opportunities of deafblind people	European Deafblind Network (2014)
	European Union, 8 countries	Nursing home residents = 32	Cross-sectional data of 4,007 nursing home residents in 59 facilities in 8 European Union countries from the Services and Health for Elderly in Long Term Care, (SHELTER) study	Visual and hearing impairments were assessed by trained staff using the interRAI instrument for long-term care facilities	Yamada et al. (2014)
6	Finland	>65 = 22.2 (LTC)> =13.4 (HC)	Finland InterRAI database, held by the National Institute for Health and Welfare (THL), approx. 35,000 assessments completed annually	The two interRAI assessment instruments (HC & LTCF) used contain approx. 3,000 items capturing multiple domain areas, with considerable overlap. Presence of DSI was determined using the Deafblind Severity Index.	Guthrie et al. (2016)
7	Ghana	5–17 years = 0.071	2010 Population and Housing Census Ghana Statistical Service Sample size 2,466,289	Does (the respondent) have any serious disability that limits his or her full participation in life activities (such as mobility, work, social life, etc.)?	WFDB Global Report 2018 Annex 2
		18–39 years = 0.088
		40–59 years = 0.180
		60–74 years = 0.540
		75+ years = 1.480
8	Iceland	>67 years = 7	Population-based cohort study of 4,926 Icelandic individuals age >67 years between 2002 and 2006	Participants were classified as having “moderate or greater” degree of impairment for vision only, hearing only, and both vision and hearing	Fisher et al. (2014)
9	Indonesia	5–17 years = 0.012	2010 Population Census Central Bureau of Statistics Sample Size 22,928,795	Washington Group of Short questions for sight and hearing (response options: none, some, and total) Deafblindness considered “total” difficulty in both domains.	WFDB Global Report 2018 Annex 2
		18–39 years = 0.110
		40–59 years = 0.025
		60–74 years = 0.310
		75+ years = 2.160
10	Ireland	5–17 years = 0.036	Census of Population of Ireland, 2011 Central Statistics Office Sample Size 474,353	Do you have any of the following long-lasting conditions or difficulties? Deafness or a serious hearing impairment (Yes/No); Blindness or a serious visual impairment (Yes/No)	WFDB Global Report 2018 Annex 2
		18–39 years = 0.047
		40–59 years = 0.150
		60–74 years = 0.470
		75+ years = 2.910
11	Japan	65–69 years = 3 >80 years = 21.9	Objective measures of vision and hearing survey of hospitalized or institutions between 2005 and 2006—Sample size 843 people aged 65 years and older	Visual and hearing impairment measures using best-corrected visual acuity and pure-tone audiometric test	Harada et al. (2008)
12	Mexico	5–17 years = 0.012	Intercensal Survey 2015 by Instituo Nacional de Estadistica, Georgrafia e Informatica (INEGI) Sample size 11,344,365	Does (the respondent) have difficulty doing the following activities in his or daily life: (a) Seeing, even when using glasses (Yes/No); (b) Hearing, even when using hearing aid (Yes/No)?	WFDB Global Report 2018 Annex 2
		18–39 years = 0.013
		40–59 years = 0.075
		60–74 years = 0.590
		75+ years = 3.540
13	Netherlands	No. of people 55 and over with acquired DSI = 30,000 to 35,000	Eight database derived from studies on older persons with vision and hearing data on Dutch subjects aged 55 years and over	The measurement methods included self-reports, clinical measurements, and observations	Vaal et al. (2007)
14	South Africa	5–17 years = 0.100	Census 2011 Statistics South Africa Sample size 4,337,697	Washington Group questions for sight and hearing. Deafblindness considered “a lot” of difficulty in both domains	WFDB Global Report 2018 Annex 2
		18–39 years = 0.066
		40–59 years = 0.220
		60–74 years = 0710
		75+ years = 2.930
15	Sudan	5–17 years = 0.012	5th Sudan Population and Housing Census 2008 by Southern Sudan Centre for Census, Evaluation and Statistics Sample size 542,765	Does (the respondent) have any difficulty in moving, seeing, hearing, speaking, or learning? (Mark all that apply) (a) difficulty hearing, (b) deaf, (c) difficulty seeing, and (d) blind	WFDB Global Report 2018 Annex 2
		18–39 years = 0.028
		40–59 years = 0.210
		60–74 years = 1.520
		75+ years = 5.660
16	Tanzania	5–17 years = 0.009	2012 Population and Housing Census by National Bureau of Statistics Tanzania Sample Size 4,498,022	Washington Group Questions for sight and hearing. Deafblindness considered “a lot” of difficulty in both domains	WFDB Global Report 2018 Annex 2
		18–39 years = 0.008
		40–59 years = 0.036
		60–74 years = 0.170
		75+ years = 1.310
	United Kingdom	Lower Estimate >59 years = 0.44 >60 years = 4.7 90+ years 18.33 Upper Estimate <59 years = 1.96 >60 years = 12.7 90+ years = 26	Multiple representative survey of National Statistics in 5 yearly intervals	Overall prevalence estimates (by gender and age) by pooling information across a number of surveys	Robertson & Emerson (2010)
		40–69 years = 3.1 of study population	National Health Service and 2001 Census data	Better-eye visual acuity with habitually worn refractive correction assessed with a logMAR chart (N=116,682). Better-ear speech reception threshold was measured with an adaptive speech in noise test, the Digit Triplet Test (N=164,770)	Dawes et al. (2014)
	United States	<70 years = <1 > 80 years = 11.3	National Health & Nutritional Examination Survey 1998–2006 of non-institutionalized civilian residents	Objective assessments of hearing and vision in a nationally representative sample—Hearing impairment defined as having a speech-frequency pure-tone average of hearing thresholds at 0.5-, 1-, 2-, and 4-kHz tones of greater than 25 dB in the better-hearing ear; Visual impairment defined as having post-auto refraction visual acuity worse than 20/40 in the better seeing-eye	Swenor et al. (2013)
	United States	75–79 years = < 1 >85 years = 11.8	465 subjects Self-reported demographic measures and co-morbid conditions study by Smith-Kettlewell Eye Research Institute longitudinal study of vision and function in the elderly	Hearing screening in conjunction with measurements on a variety of vision tests including high-contrast acuity, low-contrast acuity measured under a variety of lighting conditions, contrast sensitivity, stereopsis, and color vision	Schneck et al. (2012)
		18–44 years = 1.3	National Health Interview Survey 1997–2002 of cross-sectional civilian non-institutionalized population by National Centre of Health Statistics nationally representative sample of adults (n = 195,801) that showed concurrent hearing and visual impairment	Random health-oriented survey questionnaire on (1) Do you have any trouble seeing, even when wearing glasses or contact lenses? (2) Are you blind or unable to see at all? and (3) Which statement best describes your hearing (without a hearing aid):good, a little trouble, a lot of trouble, deaf? Participants responding yes to either of the first 2 questions were considered to be visually impaired. Participants reporting a little trouble, a lot of trouble, or that they were deaf were classified as hearing impaired.	Caban et al. (2005)
		45–64 years = 3.7
		65–79 years = 7.3
		>80 years = 16.6
		LTC >65 = 9.7 home care >65 = 15.5	InterRAI assessment data in LTCF and HC in Michigan. Approx. 27,000 in home care and approx. 90,000 in LTC facilities	InterRAI assessment completed by trained clinicians in home care/LTC facilities	Guthrie et al. (2016)
		<65 years = 0 >85 years = 26	Retrospective review of 400 medical charts of veterans receiving health care June May 2004–05. 5.7% in veteran population with DSI.	US definition of legal blindness and hearing impairment of DSI is defined only for the ear with the better pure-tone thresholds.	Smith et al. (2008)
		5–17 years = 0.110	National US Census Bureau, 2010 Sample size = 3,061,692	Is the person deaf or does he or she have serious difficulty hearing? (Yes/No) Is this person blind or does he or she have serious difficulty seeing even when wearing glasses? (Yes/No)	WFDB Global Report 2018 Annex 2
		18–39 years = 0.140
		40–59 years = 0.470
		60–74 years = 1.200
		75+ years = 5.640

dB: decibel, DSI: Dual Sensory Impairment, DSL: Dual Sensory Loss, HC: Home Care, HL: Hearing Loss, interRAI: International Resident Assessment Instrument, LTCF: Long‐Term Care Facilities; PTA: Pure Tone Average, WFDB:World Federation of the Deafblind.

Of the 19 records the majority were empirical (n = 16), followed by reports (n = 3). The studies varied in methods (e.g., population surveys, cross-sectional, and longitudinal studies). Most studies were conducted in high-income countries such as Australia, Belgium, Brazil, Canada, Denmark, Europe (27 countries and eight countries from the European Union), Finland, Iceland, Indonesia, Ireland, Japan, Netherlands, South Africa, United Kingdom, and the United States of America with the exception of the WFDB global report 2018 that collected data from low- and middle-income countries such as Ghana, Mexico, Sudan, and Tanzania. Although a good number of studies focused on all age groups of individuals with deafblindness, most study samples included those with dual-sensory loss (n = 15), followed by those with deafblindness. Only a handful of studies focused on children or on individuals with congenital deafblindness. Moreover, only one study included the older veteran population receiving health care from the U.S. Department of Veterans Affairs (Smith, Bennett, & Wilson, 2008), whereas three studies included populations from long-term care homes and home-care programs. Most studies included prevalence percentages, and some reported only ratios. The percentages have been calculated where ratios were reported.

Although the WFDB global report (2018) indicates an estimated 0.2–2% prevalence of dual-sensory impairment, this review underscores varying ranges of prevalence percentage between populations, studies or countries, age groups, and type of deafblindness.

The review highlights that the prevalence of deafblindness or dual-sensory loss varied in the literature and was often not comparable across studies or samples, but it is clear that the prevalence of dual-sensory impairment increases with age. Reasons identified by researchers for variability in prevalence rates are the use of varying sampling strategies and differing definitions of deafblindness in surveys and research, difficulties in assessing sensory functioning, inappropriate diagnosis, lack of training of professionals in identifying individuals with deafblindness, and inappropriate placement of individuals with deafblindness in programs for other disability conditions (Dammeyer, 2010, 2014; Jaiswal, Aldersey, Wittich, Mirza, & Finlayson, 2020; McInnes, 1999; Ronnberg & Borg, 2001; Sisson, Van Hasselt, & Hersen, 1987; Wittich et al., 2013, 2016).

Discussion

The review highlights the paucity of prevalence studies and provides evidence of the variability in prevalence estimates. Table 1 illustrates the variety of age groups, definitions of deafblindness, methods of assessment of the sensory disabilities, sample sizes, and databases that contribute to this prevalence variability. This variability limits the analyses and consistent reporting of prevalence estimates. Varied definitions and complex assessment methods complicate the comparison of counts and estimates across the studies. The first-ever WFDB (2018) global report included data sets from 22 countries around the world and estimated 0.2–2% prevalence rates. There is room for improving consistency of definition, methodology, and reporting. Moreover, the lack of recognition of deafblindness or dual-sensory loss in the population-based epidemiological surveys (e.g., National Population Health Survey) leads to its invisibility and underestimation, as already underscored by the WFDB (2018) global report. Although the review indicates a need for more prevalence studies from low- and middle-income countries, future prevalence studies could also consider including data from the distinct groups based on intersectionality such as ethnicity, gender, race, or immigration status that may help identify factors predicting higher or lower prevalence rates.

There is a lack of clarity for objective criteria or accepted definition for deafblindness or dual-sensory loss in research or clinical practice. Functional definitions evaluate the degree of effect that combined hearing and vision loss have on the daily functioning of the person (Ask Larsen & Damen, 2014). These functional definitions do not indicate that the person has total deafness and blindness; often, there is a residual hearing or vision or both that can be maximized for rehabilitation purposes (Dammeyer, 2014; Wittich, Watanabe, & Gagné, 2012).

It is recommended that future research studies about individuals with deafblindness include coordinated data-collection tools such as (a) standardized definitions of deafblindness or dual-sensory loss; (b) severity levels of visual and hearing impairments; (c) level of sensory functioning in relation to access to information, communication, and mobility; (d) age of onset of deafblindness or dual-sensory loss; and (e) language and communication ability at the onset of deafblindness or dual-sensory loss (Ask Larsen & Damen 2014; Dalby et al., 2009; Dammeyer, 2014; Saunders & Echt, 2007). This level of data is critical for sound scientific evidence for better comparisons from across countries.

The authors note that the WFDB (2018) global report and the CSD survey methodologies have used the standard Washington Group Short Set of Questions on Disability (National Center for Health Statistics, 2015) to assess the functional severity levels. To mitigate the challenge of cross-country age-specific comparisons over time, between-study populations, and varying methods, authors recommend the use of standard definitions of deafblindness used by the WFDB (2018) global report and an age group classification by the World Health Organization (WHO). Standard age grouping and definition classifications will facilitate linkages and improve data comparability in the field of deafblindness at the international levels, from different sources, over time, and with the same or different study samples (Department of International Economic & Social Affairs, n.d.; United Nations, 1982; WFDB, 2018). Moreover, consistency in the use of standardized definitions and age grouping could also assist with the improved coordination of data-collection tools used for census and national surveys (e.g., National Population Health Survey) to assist in gaining valuable disability-related information for program development (Washington Group on Disability Statistics, 2017). As recommended in the World Report on Disability 2011, for collecting quality of data on disability, adoption of International Classification of Functioning, Disability and Health (ICF) as a common framework for defining deafblindness may be beneficial for cross-country comparability of data. The InterRAI Community Health Assessment (interRAI CHA) with its Deafblind Supplement (DbS) tool (https://interrai.org/instrument-category/comprehensive-assessment-instruments/) has been developed with scientific rigor in order to evaluate the strengths, preferences, and needs of an individual with DSL as well as the severity levels (Guthrie et al., 2011). The authors acknowledge the limitations of DbS tool since it can only be used for adults (18 or older) living in the community and in a variety of residential care settings (other than those who are receiving formal home-care services); yet it delves deeper to gain clearer assessment information regarding the degree of impairment and status change for those who are deafblind due to both congenital and acquired means.

Footnotes

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

ORCID iD

Renu Minhas

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