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Correspondence: Address correspondence to Mark Brennan, PhD, Senior Research Associate, Arlene R. Gordon Research Institute, Lighthouse International, 111 East 59th Street, New York, NY 10022-1202. E-mail: mbrennan{at}lighthouse.org
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Abstract |
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Key Words: Vision impairment • Hearing impairment • Disability
Everyday Competence in Later Life
Everyday competence in later life is the ability to function independently in the community, and this often requires adaptation to loss in various life domains (Baltes & Lang, 1997; Diehl, 1998; Willis, 1996). Resources in sensorimotor, cognitive, personality, and social domains can offset losses and facilitate adaptation, but they can constrain adaptation when they are limited (Baltes & Lang; Diehl; Lang, Rieckmann, & Baltes, 2002). The everyday competence model posits that resource losses will have a differential effect on functional ability; namely, complex tasks will be more severely affected than basic tasks. Task complexity is largely a function of the cognitive and sensorimotor demands of the activity (Diehl; Willis). Thus, loss of competence would initially be manifested in instrumental activities of daily living (IADLs), such as managing money, before it affected more basic self-care personal activities of daily living (ADLs) such as eating or toileting (Baltes & Lang; Lang et al.; Wahl, Schilling, Oswald, & Heyl, 1999). In fact, research has confirmed that cognitive and sensorimotor resources are reliable predictors of IADL task dysfunction (i.e., managing money or using the telephone; see Wahl, Schilling et al.; Willis). Because vision and hearing function are resources in the sensorimotor domain (Baltes & Lang), the everyday competence model would predict that dual impairment would have a more severe impact on functional ability than would a single impairment, because it entails a greater loss of sensorimotor resources.
Empirical Evidence and the Competence Model of Sensory Loss
Little research has examined functional competence and dual sensory loss. However, there is a strong relation between visual impairment and functional disability among elderly individuals, even when confounding covariates are controlled for (Branch, Horowitz, & Carr, 1989; Carabellese et al., 1993; Marsiske, Klumb, & Baltes, 1997). Although hearing-impaired elderly persons may have greater functional disability than those who are nonimpaired (Carabellese et al.; Marsiske et al.; Strawbridge, Wallhagan, Shema, & Kaplan, 2000), this has not been a consistent finding (Rudberg, Furner, Dunn, & Cassel, 1993). Moreover, the impact of hearing impairment on functional ability does not appear as robust compared with that of vision loss (Crews & Campbell, 2004; Ford et al., 1988; Wallhagen, Strawbridge, Shema, Kurata, & Kaplan, 2001). Thus, vision and hearing loss may affect functional ability differentially, because vision represents a primary information pathway compared with other senses like hearing (Hershberger, 1992). Studies examining the effects of visual impairment on functional competence support the prediction of greater impact on complex IADL tasks relative to ADL abilities (Branch et al.; Furner, Rudberg, & Cassell, 1995; Horowitz, Reinhardt, McInerney, & Balistreri, 1994; Wahl, Oswald et al., 1999; Wahl, Shilling, et al., 1999; Wallhagen et al.).
Although Appollonio, Frattola, Carabellese, and Trabucchi (1989) found that dual impairment did not lead to additional deterioration of ADL and IADL ability over a single impairment, the available, albeit limited, research that exists tends to be in line with the everyday competence model. Namely, greater ADL dysfunction is related to dual impairment (i.e., greater resource loss) as compared with single impairments (Keller, Morton, Thomas, & Potter, 1999; LaForge, Spector, & Sternberg, 1992; Reuben, Mui, Damesyn, Moore, & Greendale, 1999; Smith & Kington, 1999). Crews and Campbell (2004) assessed single and dual sensory impairment in relation to ADLs among adults aged 70 and older. For all tasks, dual impairment, followed by vision impairment, and lastly hearing loss, increased the risk of difficulty compared with no sensory loss. However, Crews and Campbell did not examine the relative risk of increased difficulty between single and dual impairment, and their analyses did not control for other important covariates of functional ability, which may have overestimated the impact of dual sensory loss on everyday competence.
Purpose and Rationale
In the present study we examined the relation of dual sensory loss to functional competence among older adults. We included cognitive function in these analyses because it is an important resource domain for everyday competence (Diehl, 1998; Willis, 1996), and cognitive dysfunction and sensory loss are hypothesized to result from a "common cause" of neuropsychological aging (Lindenberger, Scherer, & Baltes, 2001; Wahl & Heyl, 2003). We build on and expand existing research by examining dual sensory loss relative to both no impairments and single impairments and functional competence, and by considering the roles of sensory loss and cognitive function on ADL ability in multivariate models that control for sociodemographic and physical health covariates. Using the everyday competence model, we made the following hypotheses:
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Measures
Sociodemographic Characteristics
We used seven measures of sociodemographic characteristics: age, gender, race, education, poverty, living alone, and proxy interview (see Table 1). Age and education were continuous variables. We dummy-coded being female, being Black, belonging to other race, living below poverty level, living alone, and using a proxy as 1 = yes and 0 = no. We included proxy interview status as a sociodemographic factor because it may result from a variety of causes (e.g., frailty, dementia).
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Cognitive Status
We used two self-assessed measures of cognitive function—trouble remembering and frequency of confusion (see Table 1). Respondents were asked, "In the past year, about how often did you have trouble remembering things or how often did you get confused—frequently, sometimes, rarely, or never." We coded answers as 3 = frequently, 2 = sometimes, 1 = rarely, and 0 = never.
Sensory Impairment
We used two self-report items to compute graded classifications of vision and hearing loss that asked, "Which statement best describes your vision [or hearing] even when wearing glasses or contact lenses [or hearing aid]—no trouble, a little trouble, or a lot of trouble?" We classified participants responding "a lot" as severely impaired, those responding "a little" as moderately impaired, and those reporting "no trouble" as not impaired. In addition, we classified individuals reporting being blind in both eyes or deaf in both ears as severely visually or hearing impaired, respectively.
We combined individual vision and hearing status variables to construct the dual sensory impairment variable; we classified individuals with two severe impairments as having severe dual, those with one severe impairment and one moderate impairment as mixed dual, and those with two moderate impairments as moderate dual impairment. We classified those with a single impairment regardless of severity as singly impaired, and the remainder we classified as no impairment.
Functional Tasks
The seven ADL tasks were bathing or showering, dressing, eating, getting in or out of a bed or chair, walking, getting outside, and toileting. The six IADL tasks were preparing meals, shopping, managing money, using the telephone, doing heavy housework, and doing light housework. For each item, we rated the degree of difficulty as none, some, a lot, or unable to do. We dummy-coded these ordinal responses because there was a large proportion of respondents reporting no task difficulty (i.e., 0 = no difficulty and 1 = difficulty; see Table 2).
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To gauge the relative effects of sensory impairment status, we performed three separate models using a different reference group of sensory impairment status (i.e., no sensory impairment, vision impairment only, or hearing impairment only) for each analysis to compare the effects of dual sensory impairment versus single impairments on the probability of having specific ADL–IADL difficulties. To control for Type I error rates for these multiple comparisons, we made a Bonferroni correction by dividing the number of reference group comparisons (i.e., three) by the alpha level of.05; thus we considered results at only the p <.01 level to be statistically significant for sensory status variables.
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Results |
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Effects of Dual Sensory Impairment on ADL–IADL Tasks
The discussion of findings focuses on the differential effects of cognition and sensory impairments on functional competence, independent of sociodemographics and physical health. However, some trends regarding the latter variables are worth noting. Greater age showed a positive relation to difficulty with all ADL and IADL tasks except eating. Women were more likely than men to report difficulty preparing meals, shopping, doing heavy and light housework, bathing, getting in and out of bed, walking, getting outside, and toileting. Blacks were more likely than Whites to report difficulty with preparing meals, shopping, doing heavy and light housework, dressing, walking, getting outside, and toileting. We found a consistent positive relationship between measures of functional disability and proxy interview, as well as all three indicators of poor comorbid health.
ADL
The effects of cognitive factors, dual impairment, and single sensory loss on ADL task difficulty are shown in Table 3.
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Dressing
Although frequency of confusion demonstrated a similar increased risk of dressing difficulty in comparison with bathing (i.e., 19%), surprisingly, trouble with memory was associated with a decrease in task difficulty by 22%. Single sensory impairments did not increase the probability of difficulty with dressing. In terms of dual sensory impairment, elders with all levels of dual sensory impairments were approximately twice as likely to report difficulty with dressing as respondents with no sensory impairments or hearing impairment only. However, when referenced against elders with single impairments in vision, dual sensory impairment did not represent additional risk of task difficulty.
Eating
Frequency of confusion increased the risk of difficulty with eating by 60%, but we found no significant effects for memory. Single and dual sensory impairment did not significantly increase the risk of difficulty with eating.
Getting in and out of Bed
Cognitive status was not associated with risk of difficulty with this activity. Overall, single vision or hearing impaired older adults did not have a greater risk of difficulty with getting in and out of bed relative to their nonimpaired counterparts. Severely dual sensory impaired elders were the most likely to have difficulty in getting in and out of bed; they were almost 2.5 times more likely than nonimpaired elders, and almost twice as likely to report difficulty compared with those who were singly hearing impaired. However, dual sensory impairment did not increase the risk of difficulty with this task relative to single vision impairment.
Walking
As in some other ADL tasks, whereas frequency of confusion increased the risk of walking difficulty by 10%, trouble with memory was associated with a 12% decrease in the likelihood of difficulty. Single vision impaired elders were 46% more likely than those with no sensory impairments to report walking difficulty. Single hearing loss was not associated with difficulty in walking. Dual sensory impaired elderly persons exhibited a greater difficulty in walking when compared with their nonimpaired or singly hearing impaired counterparts. However, there was no increased risk in walking difficulty associated with dual sensory loss over single vision impairment.
Getting Outside
Trouble with memory was related to a decrease in the likelihood of difficulty in getting outside (i.e., 18%) similar to other ADL tasks, but confusion was not related to this activity. Compared with unimpaired elders, those who were vision impaired only were 60% more likely to have difficulty getting outside. Hearing impairment was not associated with greater difficulty. Mixed dual impaired elderly individuals also had an 86% greater risk of such difficulty than the nonimpaired individuals. However, when referenced against single impairments in vision, dual sensory impairment was no longer significant. Thus, vision impairment by itself contributed to a greater risk of difficulty in getting outside, whereas having a hearing impairment did not significantly increase the risk of task difficulty.
Toileting
Frequency of confusion increased the risk of difficulty with toileting by 27%, although trouble with memory was not related to task difficulty. Furthermore, none of the sensory impairment variables was significantly associated with difficulty in using the toilet.
IADL
The effects of cognitive factors, dual impairment, and single sensory loss on IADL task difficulty are shown in Table 4.
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A more complex picture emerges when we examined the three levels of dual impairment relative to a single impairment in vision. Having a severe dual impairment continued to have a negative effect on ability to prepare one's meals, over and beyond that accounted for by the vision impairment, suggesting that the effect of dual impairment on meal preparation is most likely evidenced with the highest level of vision impairment (i.e., a lot of trouble rather than a little trouble). Hearing impairment did not contribute to risk for difficulty with this task.
Shopping
Cognitive status variables were not significantly related to risk of difficulty with shopping. Single vision impairment, but not hearing impairment, accounted for greater reported difficulty with shopping. Visually impaired elders had a greater risk of reporting difficulty in shopping than those without any sensory loss and compared with elders with hearing impairment only. In contrast, having a single impairment in hearing was not related to increased task difficulty compared with having no impairment. Whereas having a moderate dual impairment did not significantly increase shopping difficulty compared with having no impairment, having a mixed or severe dual impairment sharply increased the risk. Furthermore, severe dual impairment continued to be associated with difficulty in shopping, over and beyond that accounted for by vision impairment alone. Because moderate dual impairment actually showed a 47% decrease in the risk of shopping difficulty when referenced against single impairment in vision, this suggests again that the negative effects of vision on the ability to shop are mostly evident at higher levels of impairment.
Managing Money
Frequency of confusion was associated with a 52% increased risk for difficulty in managing money, but memory trouble was not related to this complex IADL task. Respondents with a single impairment in vision had more than 3 times the risk of reporting difficulty in managing money than those without any sensory impairment. In contrast, singly hearing impaired elders did not differ in their ability to manage money compared with the unimpaired. Having a mixed dual impairment or a severe dual impairment significantly increased the risk of difficulty with money management. However, having a moderate dual impairment did not significantly predict difficulty in this task relative to having no impairment. Mixed and severely dual impaired elders were also more likely to have increased difficulty with money management than the single hearing impaired. As was true of other IADL tasks, the effect of vision loss on the ability to manage money is more pronounced at higher levels of vision loss. Relative to a single impairment of vision, mixed or severe dual impairment were not associated with difficulty in managing money. However, moderate dual impaired elders had a 61% decreased risk of difficulty compared with elders reporting vision impairment only. These results suggest that severe vision impairment was responsible for most of the risk in difficulty with money management.
Using the Telephone
Similar to managing money, frequency of confusion increased the risk of difficulty of using the telephone by nearly 50%, but trouble with memory was not related to task difficulty. The negative effects of vision and hearing impairments on the ability to use a telephone increased greatly among elders with higher levels of sensory losses. Single impairments of both vision and hearing increased the probability of having difficulty with telephone use. Severe dual sensory impairment significantly increased the risk of difficulty with telephone use over and above that accounted for by single visual impairment. We obtained similar results when comparing these dual impairment levels to a single impairment of hearing, except that those with mixed dual loss were also at greater risk. We found no significant differences between singly vision impaired and singly hearing impaired elders in the ability to use the telephone.
Heavy Housework
Cognitive status variables were not significantly related to difficulty with heavy housework. However, vision impairment, but not hearing impairment, increased the risk of reporting difficulty with heavy housework. Singly vision impaired elders were 120% more likely to report difficulty in performing heavy housework compared with those with no sensory impairment, and they had a 47% greater risk than elders with a single hearing impairment. We found no differences between singly hearing impaired and nonimpaired elderly persons in reporting difficulty with this task. Dual sensory impairment did not significantly increase the risk of difficulty with heavy housework over that accounted for by vision impairment alone.
Light Housework
As was the case with heavy housework, cognitive status was not significantly related to task difficulty. Single sensory impairments were also not associated with a greater task difficulty compared with no sensory impairment. Although having a moderate dual impairment was not associated with difficulty in this task relative to having no impairment, having a mixed or a severe dual impairment significantly increased the risk of difficulty. Although there was no significant difference in ability to do light housework when we compared the singly hearing impaired elderly individuals with those who were not impaired, the odds ratios for the two highest levels of dual sensory impairment were significantly greater relative to a single impairment in hearing. Thus, vision impairment appeared to be responsible for the effects of dual impairment on the ability to do light housework, whereas hearing impairment was not a significant factor.
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Regarding ADL tasks, our hypotheses were partially supported. Dual impairment increased the risk of difficulty with these activities compared with hearing impairment only and no impairment, but it did not significantly increase risk over and above vision impairment. In addition, significant risks associated with sensory impairment and ADL difficultly were more modest than those for IADL tasks. This result is consistent with the competence model's prediction that resource loss would have a greater impact on complex tasks than on simple ones. However, among the cognitive status variables, we did not expect the finding of a more pervasive role of confusion in increasing risk of difficulty with ADL as compared with IADL tasks; we also did not expect the finding that trouble with memory was associated with decreased risk in certain tasks (i.e., dressing, walking, and getting outside), as this was contrary to hypotheses generated with the competence model.
The multiple-comparison approach used in the current study allowed functional disabilities resulting from single impairments to be examined separately from those resulting from dual impairment, which is an advance over previous examinations of the role of sensory loss and functional competence. This approach has revealed that most of the functional difficulty associated with dual sensory loss may be attributable to vision loss rather than hearing impairment, inasmuch as vision is the primary sense for obtaining information (Hershberger, 1992). However, similar to the study by Crews and Campbell (2004), the present study found that older adults with dual sensory loss experienced greater functional disability than older adults who were unimpaired. Higher levels of dual sensory impairment were shown to increase the risk of disability in three of the six IADL tasks (i.e., preparing meals, shopping, and using the telephone) over and beyond that accounted for by vision impairment. These findings are consistent with previous studies that found dual sensory loss to have a greater impact on functional disability than that seen with a single impairment (Crews & Campbell; Keller et al., 1999; Reuben et al., 1999; Smith & Kington, 1999).
Study Limitations
Although one of the strengths of the present analysis was the use of a large, nationally representative sample of older adults, limitations of these data were that analyses were cross-sectional and that all covariates were obtained through self-report. The self-report nature of the data may be responsible for the unexpected finding in which trouble with memory was related to decreased difficulty on three of the seven ADL tasks. Namely, self-rated memory measures often fail to correspond with actual cognitive performance (Zelinski & Gilewski, 2004). We were limited in choices of variables representing cognitive status because of the secondary nature of these data, and we recommend that future research in this area should use measures of cognitive function with better psychometric properties.
Diehl (1998) further noted a number of problems with self-report of functional ability, including overestimation and underestimation of function depending on contextual factors. However, Diehl also noted that there are problems with more objective approaches (i.e., proxy ratings, objective performance) and suggested a triangulation approach of self-report, proxy reports, and performance measures. This is a recommendation we support for future research in this area. Self-report on sensory and cognitive status may also have yielded biased estimates, so a multiple measurement approach for these factors appears warranted. Finally, the present analyses did not account for important personality and social support resources that also are considered fundamental in explanations of everyday competence (Baltes & Lang, 1997; Diehl; Lang et al., 2002). Future research should include these domains in studies of cognition, sensory status, and functional ability.
Study Implications
Despite limitations of the present study, data suggest that elderly persons with dual sensory loss and single impairments of vision are at risk for decreased everyday competence and the capacity for independent living. Abnormal changes to vision and hearing in later life are often mistaken for normative aging, and decrements to these senses result in poorer quality of life for those affected and their significant others (Crews & Campbell, 2004; Glass, 2000; Wahl & Heyl, 2003). Thus, outreach should be expanded on the prevention, identification, and rehabilitation options for older adults with single and dual sensory loss.
Given the high prevalence of single and dual sensory loss in the older population, vision and hearing screening should be part of any regular physical assessment for older individuals. Health, social service, and rehabilitation providers also need better training in the identification of sensory impairment, which may be concealed by the older person because of the stigmatization of these conditions (Glass, 2000). In addition, service providers should receive training in methods that optimize communication with older adults experiencing dual sensory loss (LeJeune, Steinman, & Mascia, 2003).
Present findings suggest that both vision and dual sensory loss have a greater impact on IADL compared with ADL tasks, which is important in the planning and targeting of rehabilitation services. Vision and aural rehabilitation programs should examine current practices in order to optimize training and assistance with IADL tasks. Unfortunately, knowledge and utilization of available sensory rehabilitation programs is low (Horowitz, Reinhardt, & Brennan, 1997). Such lack of knowledge represents a barrier to services, and ultimately it can result in excess disability among those with sensory impairments. Thus, outreach and education of aging professionals on sensory rehabilitation may be one method of bridging this gap.
Greater access to health care for visual and auditory examinations also could reduce the prevalence of sensory loss in later life caused by preventable and treatable disease. Unfortunately, most insurance plans cover neither routine vision and hearing examinations nor sensory rehabilitation to minimize the disabling effects of sensory loss. Although a Medicare demonstration project to cover vision rehabilitation services was included in the Medicare Modernization Act of 2004, more has to be done to ensure that older people with sensory loss have access to services that promote independent living. It is far more cost effective to help these individuals maintain their independent status through rehabilitation programs than to deal with the consequences of disability in terms of continuing declines in mental and physical health associated with disability.
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Footnotes |
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1 Arlene R. Gordon Research Institute, Lighthouse International, New York, NY.
2 The Peer Review Organization of New Jersey, East Brunswick, NJ.
Decision Editor: Linda S. Noelker, PhD
Received for publication April 1, 2004. Accepted for publication October 27, 2004.
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