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

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.

Association of Dual Sensory Impairment with Incident Mobility and ADL Difficulty

Hearing and vision impairment are each independently associated with incident mobility disability and disability in activities of daily living (ADL). Whether dual sensory impairment (DSI) in both hearing (pure-tone average >25 dB) and vision (impaired visual acuity and/or impaired contrast sensitivity) is associated with greater risk of incident mobility and ADL difficulty, as compared to single or no sensory impairments, has not been well-studied. To examine these associations, we used data from 2,020 Health Aging and Body Composition Study participants aged 70-79 years without mobility limitations. Incident mobility difficulty was defined as the first instance of a lot of problems or inability to walk ¼ mile and/or climb 10 steps, and incident ADL difficulty was defined as the first instance of problems with any ADL. Cox proportional hazards models adjusted by demographic covariates, diabetes, hypertension, and depressive symptoms were used to model these associations. Approximately 22.7% of the study had DSI. DSI was associated with increased risk of both incident mobility (Hazard Ratio [HR]=2.43, 95% Confidence Interval [CI]: 1.60, 3.69) and ADL difficulty (HR=2.39, 95% CI: 1.60, 3.56). Vision impairment only was associated with risk of incident mobility difficulty (HR=1.74, 95% CI: 1.09, 2.78), but not incident ADL difficulty (HR=1.45, 95% CI: 0.91, 2.32). Hearing impairment only was not associated with risk of either outcome. Synergistic effects of DSI on the additive scale were present. Sex and race did not modify associations. Monitoring of DSI may be beneficial in delaying incident difficulty.

Prevalence of Concurrent Functional Vision and Hearing Impairment and Its Association with Dementia

Vision and hearing impairment are common and independently linked to dementia risk. Adults with concurrent vision and hearing impairment (dual sensory impairment, DSI) may be particularly at-risk. Data were from the National Health and Aging Trends Study (NHATS) (2011–2018, N=7,562). Functional sensory impairments were self-reported (no impairment, vision only, hearing only, and DSI). We calculated age-specific prevalence of sensory impairments. Discrete time proportional hazards model with a complementary log-log link were used to assess 7-year dementia risk. Of 7,562 participants, overall prevalence of functional vision, hearing and DSI was 5.4%, 18.9% and 3.1%, respectively. DSI prevalence increased with age, impacting 1 in 7 adults ≥90 years. DSI was associated with a 50% increased 7-year dementia risk (adjusted hazard ratio 1.50; 95% confidence interval, 1.12–2.02) compared to no impairment. Sensory rehabilitative interventions for multiple impairments may be an avenue for consideration in efforts to reduce dementia risk.

Unraveling the genetic complexities of combined retinal dystrophy and hearing impairment

Usher syndrome, the most prevalent cause of combined hereditary vision and hearing impairment, is clinically and genetically heterogeneous. Moreover, several conditions with phenotypes overlapping Usher syndrome have been described. This makes the molecular diagnosis of hereditary deaf–blindness challenging. Here, we performed exome sequencing and analysis on 7 Mexican and 52 Iranian probands with combined retinal degeneration and hearing impairment (without intellectual disability). Clinical assessment involved ophthalmological examination and hearing loss questionnaire. Usher syndrome, most frequently due to biallelic variants in MYO7A (USH1B in 16 probands), USH2A (17 probands), and ADGRV1 (USH2C in 7 probands), was diagnosed in 44 of 59 (75%) unrelated probands. Almost half of the identified variants were novel. Nine of 59 (15%) probands displayed other genetic entities with dual sensory impairment, including Alström syndrome (3 patients), cone-rod dystrophy and hearing loss 1 (2 probands), and Heimler syndrome (1 patient). Unexpected findings included one proband each with Scheie syndrome, coenzyme Q10 deficiency, and pseudoxanthoma elasticum. In four probands, including three Usher cases, dual sensory impairment was either modified/aggravated or caused by variants in distinct genes associated with retinal degeneration and/or hearing loss. The overall diagnostic yield of whole exome analysis in our deaf–blind cohort was 92%. Two (3%) probands were partially solved and only 3 (5%) remained without any molecular diagnosis. In many cases, the molecular diagnosis is important to guide genetic counseling, to support prognostic outcomes and decisions with currently available and evolving treatment modalities.

Dual Sensory Impairment and Cognitive Impairment in the Korean Longitudinal Elderly Cohort

Objective:To investigate the effects of single sensory impairment (SSI; visual or auditory) or dual sensory impairment (DSI; visual and auditory) on dementia and longitudinal changes of neuropsychological test scores.Methods:In this nationwide, prospective, community-based elderly cohort study, Korean Longitudinal Study on Cognitive Aging and Dementia (KLOSCAD), 6,520 elderly individuals (58-101 year) representing the general population were included. We defined visual and auditory sensory impairment via self-report questionnaire: 932 had a normal sensory function, 2957 had a SSI, and 2631 had a DSI. Demographic and clinical variables including cognitive outcomes were evaluated every two years over six years. Through logistic regression, Cox regression, and linear mixed model analysis, the relationship between SSI or DSI and dementia prevalence, dementia incidence, and change in neuropsychological scores were evaluated.Results:At baseline, DSI was significantly associated with increased dementia prevalence compared to normal sensory function (OR=2.17, 95% CI [1.17–4.02]), but SSI was not (OR=1.27, 95% CI [0.66–2.41]). During the 6-year follow-up, the incidence of dementia was significantly higher in the DSI group than in the normal sensory function (HR=1.9, 95% CI [1.04–3.46]), and neuropsychological scores significantly decreased (β=-0.87, 95% CI [-1.17–-0.58]).Conclusions:Our results suggest that coexisting visual and hearing impairments facilitate dementia prevalence, dementia incidence, and cognitive decline, but visual or hearing impairment alone do not. Additionally, visual and hearing impairment may lead to dementia or cognitive decline independent of Alzheimer’s pathology.