405495 Miller et al.Journal of Applied Gerontology © The Author(s) 2013
JAG32110.1177/0733464811405495
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Article
Activities of Daily Living Are Associated With Older Adult Cognitive Status: Caregiver Versus Self-Reports
Journal of Applied Gerontology 32(1) 3–30 © The Author(s) 2013 Reprints and permission: sagepub.com/journalsPermissions.nav DOI: 10.1177/0733464811405495 http://jag.sagepub.com
L. Stephen Miller1, Courtney L. Brown1, Meghan B. Mitchell1, and Gail M. Williamson1 Abstract We compared the extent to which subjective report of activities of daily living (ADLs) by caregivers and older adults were associated with objective measures of older adults’ cognition. In independent studies (Study 1 N = 238; Study 2 N = 295), bivariate correlations and multiple regression analyses examined the association of caregiver and self-rated reports of older adult basic, instrumental, and total ADLs and older adult cognition. We examined the magnitude of the caregiver/ self-report discrepancy and older adult cognition. In both studies, caregiver reports more accurately accounted for older adult cognitive differences. Older adult visuospatial/constructional deficits were uniquely related to caregiver basic ADL reports. Results indicate that caregiver reports of older adult ADLs are more reliable indicators of older adult cognition than self-reports, and this difference grows as older adult cognition decreases. Thus, older adult ADL assessment may be useful in providing information on potential cognitive decline. Keywords functional status, informant report, caregiver, care recipient dyads, cognitive status Manuscript received: June 21, 2010; final revision received: December 19, 2010; accepted: February 1, 2011. 1
University of Georgia, Athens, GA, USA
Corresponding Author: L. Stephen Miller, PhD, Department of Psychology, Psychology Building, University of Georgia, Athens, GA 30602-3013, USA Email: [email protected]
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Journal of Applied Gerontology 32(1)
Older adults adapt to declining physical and cognitive capabilities, in part, with informal assistance with daily activities from close relatives. A clear and objective method for quantifying needed assistance is critical for health care providers, particularly for older adults who may evidence some level of cognitive impairment. However, it can be a challenge to integrate objective measures of cognitive function with self- and caregiver reports of daily functioning. Integrating objective and subjective measures may prove particularly daunting for health care providers who are faced with discrepant reports regarding daily functioning, as this depends on the nature and validity of responses on these measures. Although functional issues may arise in the absence of cognitive difficulties (e.g., Bennett et al., 2006), functional impairment is frequently associated with cognitive decrements and is a key criteria for dementia diagnosis (American Psychiatric Association, 2000; Dodge et al., 2005; Freilich & Hyer, 2007). Thus, it is critical to understand the association between reports of daily functioning and cognitive status. Functional impairment has frequently been assessed through use of self-report or caregiver report of activities of daily living (ADL). ADLs have been classified into two domains: Basic ADLs (BADLs) involve less complex, implicitly learned activities, such as bathing, dressing, and eating (Katz, Ford, Moskowitz, Jackson, & Jaffe, 1963). Instrumental ADLs (IADLs) involve more cognitively demanding tasks, such as managing money or medication (Lawton & Brody, 1979). Previous research has demonstrated a relationship between accuracy of selfreported functional ability and level of cognitive impairment in nondemented community-based older adults (Mitchell & Miller, 2008a) but has not evaluated that relationship directly against informant report relationships and cognition. This emphasizes the need for accurate report of functional status to attain associative validity. A roadblock to accuracy in reporting involves potential bias within reports of functional status. Although obtaining self-report remains an important factor in identifying functional limitations (Elam et al., 1991), older adults may not selfreport such problems to a physician or other health professional. Researchers have found that older adults frequently overestimate their functional abilities. This could be a result of denying difficulties as a coping mechanism, a desire to not appear as a burden to others, or a misperception of current abilities (Rubenstein et al., 1984). However, caregiver reports of functional status may also have inaccuracies. Cotter, Burgio, Stevens, Roth, and Gitlin (2002) examined the correlation between caregiver report of assistance with ADL tasks and behavioral observation of this assistance within the home. Caregivers were found to be accurate reporters of the nature of assistance when compared with behavioral observation, although they tended to overestimate the amount of time it took to provide assistance to older
Downloaded from jag.sagepub.com at GEORGIAN COURT UNIV on May 10, 2015
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Miller et al.
adults. Other researchers have shown caregivers to report more pervasive exaggerations of older adult functional deficits, perhaps as a result of caregiver burden (Rubenstein et al., 1984). Some researchers have shown no effect of variables such as relationship of caregiver to older adult or amount of caregiver time spent with an older adult as related to the discrepancy between caregiver and self-report (Farias, Mungas, & Jagust, 2005). Others have shown that live-in spouse caregivers are associated with higher ratings of accuracy (Ready, Ott, & Grace, 2004). Such potential biases make the relationship between caregiver reports and objectively measured indices of older adult function more complex. Accuracy of caregiver report has been related to decrements in older adult functional and cognitive domains. A study contrasting caregiver-reported ADLs and behaviorally observed ADLs in older adults exhibited strong correlations in the domain of motor functioning (walking) and moderately strong correlations in other basic activities (dressing). Correlations were weaker for IADLs, such as managing money (Zanetti, Geroldi, Frisoni, Bianchetti, & Trabucchi, 1999). Studies focusing on IADLs have similarly shown weak accuracy of self- and informant reports of financial abilities, consistent older adult overestimation of skills, and low stability of both types of reports (Wadley, Harrell, & Marson, 2003). Research reporting changes in cognitive status suggest that older adult decrements in memory predict a self-report–caregiver report discrepancy (Farias et al., 2005). A growing literature has investigated the association between cognitive deficit and functional status. Dodge et al. (2005) estimated that cognition accounted for 18% to 36% loss in BADL abilities and 11% to 29% of loss in IADL abilities in a community-based sample of older adults. Longitudinally, cognitive impairment at baseline in participants experiencing no functional decrement was a risk factor for later decline (1 year post baseline) in BADLs and IADLs (Dodge et al., 2005). Bennett et al. (2006) suggested global cognitive functioning accounted for up to 22% of the variance in functional status, particularly within the domain of housework but found no specific cognitive domain that was uniquely related to functional status. However, several studies suggest that executive functioning plays a significant role in facilitating activities of daily living (Grigsby, Kaye, Baxter, Shetterly, & Hamman, 1998; Lewis & Miller, 2007; Mitchell & Miller, 2008a, 2008b). After controlling for demographic factors, Johnson and colleagues found that decrements in executive functioning, as measured by the Trails B test, were predictive of later decline in ADLs in female older adults (Johnson, Lui, & Yaffe, 2007). Others suggest that cognitive and physical processes independently contribute to an individual’s ability to complete ADLs (Gill, Williams, Richardson, & Tinetti, 1996; Petrella, Cress, & Miller, 2004).
Downloaded from jag.sagepub.com at GEORGIAN COURT UNIV on May 10, 2015
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Journal of Applied Gerontology 32(1)
The current investigation sought to examine caregiver versus self-report of functional status and their relationship to objective measures of cognitive function. In the current investigation, we compared caregiver and self reports of BADLs and IADLs as they relate to measures of cognition in older adults. Discrepancies within the current literature associating the role of caregiver and self-report with older adult cognition are difficult to reconcile due to variability in methodology and sample size across studies. To account for such issues, we used two samples of community-based dyads, with both older adult and caregiver in each sample completing nearly identical functional report measures. Another aim of the current study was to use a large sample size of caregiver– older adult dyads and specifically employ common clinical measures of cognition to evaluate the relationship between reported functional status and cognition. We used the Cognistat: Neurobehavioral Cognitive Status Examination (Cognistat; Northern California Neurobehavioral Group, Inc., 1995; Kiernan, Mueller, Langston, & Van Dyke, 1987) and the Repeatable Battery for the Assessment of Neuro psychological Status (RBANS; Randolph, 1998) to compare the correlation of functional measures with neuropsychological measures commonly used in geriatric populations. We sought to identify the relationship between older adult cognitive status and reported functional status and also to examine what domains of cognition may hold the most associative power in caregiver report of older adult functional status. Domains of cognitive function associated with caregiver reports on older adult functional impairment would be helpful for clinicians to clarify what aspects of cognitive decline may be most readily observed when assessing older adult functional status by self- and collateral report. Based on the extant literature, we hypothesized that (a) caregiver reports of older adult total ADLs would be more highly associated with older adult cognition than self-reports of total ADLs; (b) caregiver reports of older adult BADLs and IADLs would each be more strongly associated with cognition than selfreport; and (c) IADLs would be more highly associated with cognition than BADLs, regardless of report method. In testing the above hypotheses, we separately analyzed data from two different studies. In Study 1, participants were drawn from the Family Relationships in Late Life (FRILL) study (described below), in which the Cognistat was used as a measure of older adult cognition. In Study 2, participants included caregiver– older adult dyads from the second FRILL study (FRILL2), including an oversampled set of African American dyads. In Study 2, the RBANS was used as a measure of older adult cognition. Furthermore, in identifying an associative relationship between caregiver reports of older adult total ADL and older adult RBANS scores, we sought to
Downloaded from jag.sagepub.com at GEORGIAN COURT UNIV on May 10, 2015
7
Miller et al.
isolate specific domains of cognitive function that could drive this relationship. In Study 2, we expanded our comparison of BADLs and IADLs tested in Study 1 by also examining specific domains of cognitive functioning as they relate to the maintenance of daily functioning. We were interested in whether the relationship between cognitive functioning and both BADLs and IADLs tested within Study 1 were being driven by particular cognitive processes. Specifically, we were interested in determining which components of cognition were essential for the maintenance of simple versus complex activities of daily living (i.e., BADLs vs. IADLs). To accomplish this goal, we reversed associated variables to directly compare the variance in functional status (caregiver reported older adult BADL and IADL) accounted for by five RBANS index scores. We hypothesized that (a) the older adult performance on RBANS indices of visuospatial and attentional tasks would be most highly associated with BADL decrements because these fundamental activities (e.g., dressing, grooming, bathing) require visuomotor coordination, speed, and spatial navigation. In contrast, we hypothesized that (b) older adult performance on RBANS indices of language and delayed memory would be the most highly associated with IADL decrements because these more complex activities (e.g., managing finances, managing medications, grocery shopping) require higher order cognitive abilities such as naming ability, verbal fluency, and memory functioning. In addition, language and delayed memory functioning are most likely to decline in preclinical Alzheimer’s disease (Randolph, 1998) and decrements in these domains may be more likely in individuals experiencing functional decline in IADLs. We chose to use caregiver report of older adult ADL functioning because Study 1 findings suggested that caregiver ratings of older adult functional status were more sensitive (i.e., larger range in scores and higher mean rating of functional decrements).
Study 1 Method Sample and Procedures. In Study 1, participants were drawn from the FRILL study of informal caregiver–older adult dyads, recruited from three recruitment sites: Athens, Georgia; Pittsburgh, Pennsylvania; and Dallas, Texas. Caregivers were defined as those who provided unpaid assistance with at least two IADLs (e.g., managing money) or one BADL (e.g., bathing) to community-dwelling adults aged 60 years or older. The source of older adult impairment was not a factor in participant selection. Details of the FRILL protocol have been reported elsewhere (Beach et al., 2005; Miller et al., 2006).
Downloaded from jag.sagepub.com at GEORGIAN COURT UNIV on May 10, 2015
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Journal of Applied Gerontology 32(1)
The FRILL project was approved by all necessary institutional review boards. Participants were screened by telephone for eligibility and then interviewed in person within their homes. Caregivers and care recipients were interviewed concordantly and separately to prevent data contamination. Research staff were properly trained on interview procedures and assessment administration. Each individual received US$20 for their participation. Testing lasted 1.5 to 2 hr per participant. Recruitment efforts yielded a total of 283 dyads. Because of the extremely small number of dyads being neither White nor African American (4 dyads in “Other” category), we excluded those dyads, creating a dichotomous category for older adult race (n = 279, coded as 1 = White, 2 = African American). Of the 279 remaining dyads, 41 were excluded from analyses due to missing data on the primary measures of interest (older adult demographics; caregiver and self reports of BADLs and IADLs; older adult composite Cognistat score) leaving 238 dyads.
Measures Older adult cognitive status. Older adults completed the Cognistat (Northern California Neurobehavioral Group, Inc., 1995), which examines general cognitive functioning in 10 domains (orientation, attention, language comprehension, memory, design construction, language repetition, naming, calculations, reasoning, and judgment) and has been shown to have good sensitivity in distinguishing cognitively impaired adults in older adults (Drane & Osato, 1997). Due to limited sample sizes in published normative data for the Cognistat, we followed Miller and colleagues’ (2006) impairment rating procedure to create a composite severity score for each participant. A rating scale of 1 to 4 was created for each domain, with 1 representing lack of impairment, and 4 representing severe impairment in a given area. The summed composite rating for each individual domain was used as an estimate of older adult cognitive functioning (range = 10-40). Older adult and caregiver reported amount of help provided. Both the caregiver and older adult completed an 18-item assessment, adapted from the ADL instrument (Older American Resources and Services, Duke University, 1978) to assess older adult level of functional status. The older adult’s performance of BADLs and IADLs were based on a metric of 0 to 5. Activities that older adults had never participated in were rated 0 (e.g., if an older adult had not participated in managing couple’s money prior to impairment), to differentiate preimpairment delegated activities from level of postimpairment assistance. Activities that older adults had engaged in preimpairment received a rating between 1 and 5: A score of 1 on the scale represented activities which the older adult completed with no help, whereas a 5 represented an activity requiring a great deal of help by the caregiver. Total ADL scores have a theoretical range of 0 to 90, BADLs range
Downloaded from jag.sagepub.com at GEORGIAN COURT UNIV on May 10, 2015
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Miller et al.
from 0 to 50, and IADL range from 0 to 40. In addition, discrepancy scores were calculated by subtracting self-rated ADLs from caregiver reported older adult functional status to have a single measure of the relative size differences between caregiver and self-reports of functional status.
Results Sample Description. Mean caregiver age was 62 years (SD = 15, range = 20-88
years), and mean older adult age was 77 years (SD = 8.4, range = 60-98 years). Similar to national estimates (e.g., National Alliance for Caregiving & AARP, 2004), the majority of participants in the caregiver role were female (78%) and either a spouse (48%) or adult child (37%). Education and race for both studies are reported in Table 1. Cognitive and Functional Status. Older adults demonstrated a wide range of abilities in both cognitive domains, based on Cognistat summed composite rating, as well as within functional domains, based on self- and collateral reports of BADLs and IADLs (see Table 1). Bivariate Analysis. Older adult education and race correlated with their Cognistat composite score (r = −.334, p < .001; r = .244, p < .001, respectively), with lower Cognistat scores (higher functioning) seen more frequently in higher educated individuals and in White samples. Caregiver education and ethnic background similarly correlated with older adult Cognistat score (r = −.149, p < .05, and r = .263, p < .001, respectively). Neither older adult nor caregiver gender showed significant correlations with measures of functional status and so were not included in further analyses. Caregiver-reported older adult total ADL correlated positively with older adult Cognistat composite score (r = .296, p .05). Older adult composite Cognistat score was significantly correlated with both self-reported and caregiverreported IADLs (caregiver: r = .404, p < .001; older adult: r = .182, p .05; caregiver IADL: β = .349, t = 5.766, p < .001). To compare the impact of the overall magnitude of differences between caregiver and self-reports of both BADLs and IADLs, we ran a regression analysis using our discrepancy score variable. The discrepancy between caregiver and self-rated BADL scores were significantly associated with older adult cognition, ΔR2 = .03, ΔF(1, 234) = 8.756, p < .01. Interestingly, when the discrepancy between caregiver and self-rated IADL scores were added to the model to identify unique variance accounted for by IADLs above and beyond that accounted for by BADLs, the discrepancy scores of BADL and IADL functioning appeared to share variance. This step did not display significant
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Table 2. Study 1 Regression Analysis for Prediction of Cognistat Composite Score by Older Adult and Caregiver Demographic Variables and Total ADL Measures and Older Adult–Caregiver Total ADL Discrepancy Score Step
β
Variables entered
Total ADL measures 1A Caregiver race .228 Older adult education −.308 Caregiver race .231 1B Older adult education −.299 .056 Self-reported total ADL Caregiver race .200 1C Older adult education −.295 −.127 Self-reported total ADL .320 Caregiver-reported total ADL Caregiver–older adult combined BADL/IADL discrepancy score 2A Caregiver race .228 Older adult education −.308 Caregiver race .201 2B Older adult education −.321 .201 Caregiver–older adult total ADL discrepancy score Step 1A/2A 1B 2B 1C
t
p
3.787 −5.124 3.832 −4.914 0.930 3.428 −5.044 −1.794 4.555
JAG32110.1177/0733464811405495
Reprints and permission: sagepub.com/journalsPermissions.nav
Article
Activities of Daily Living Are Associated With Older Adult Cognitive Status: Caregiver Versus Self-Reports
Journal of Applied Gerontology 32(1) 3–30 © The Author(s) 2013 Reprints and permission: sagepub.com/journalsPermissions.nav DOI: 10.1177/0733464811405495 http://jag.sagepub.com
L. Stephen Miller1, Courtney L. Brown1, Meghan B. Mitchell1, and Gail M. Williamson1 Abstract We compared the extent to which subjective report of activities of daily living (ADLs) by caregivers and older adults were associated with objective measures of older adults’ cognition. In independent studies (Study 1 N = 238; Study 2 N = 295), bivariate correlations and multiple regression analyses examined the association of caregiver and self-rated reports of older adult basic, instrumental, and total ADLs and older adult cognition. We examined the magnitude of the caregiver/ self-report discrepancy and older adult cognition. In both studies, caregiver reports more accurately accounted for older adult cognitive differences. Older adult visuospatial/constructional deficits were uniquely related to caregiver basic ADL reports. Results indicate that caregiver reports of older adult ADLs are more reliable indicators of older adult cognition than self-reports, and this difference grows as older adult cognition decreases. Thus, older adult ADL assessment may be useful in providing information on potential cognitive decline. Keywords functional status, informant report, caregiver, care recipient dyads, cognitive status Manuscript received: June 21, 2010; final revision received: December 19, 2010; accepted: February 1, 2011. 1
University of Georgia, Athens, GA, USA
Corresponding Author: L. Stephen Miller, PhD, Department of Psychology, Psychology Building, University of Georgia, Athens, GA 30602-3013, USA Email: [email protected]
Downloaded from jag.sagepub.com at GEORGIAN COURT UNIV on May 10, 2015
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Journal of Applied Gerontology 32(1)
Older adults adapt to declining physical and cognitive capabilities, in part, with informal assistance with daily activities from close relatives. A clear and objective method for quantifying needed assistance is critical for health care providers, particularly for older adults who may evidence some level of cognitive impairment. However, it can be a challenge to integrate objective measures of cognitive function with self- and caregiver reports of daily functioning. Integrating objective and subjective measures may prove particularly daunting for health care providers who are faced with discrepant reports regarding daily functioning, as this depends on the nature and validity of responses on these measures. Although functional issues may arise in the absence of cognitive difficulties (e.g., Bennett et al., 2006), functional impairment is frequently associated with cognitive decrements and is a key criteria for dementia diagnosis (American Psychiatric Association, 2000; Dodge et al., 2005; Freilich & Hyer, 2007). Thus, it is critical to understand the association between reports of daily functioning and cognitive status. Functional impairment has frequently been assessed through use of self-report or caregiver report of activities of daily living (ADL). ADLs have been classified into two domains: Basic ADLs (BADLs) involve less complex, implicitly learned activities, such as bathing, dressing, and eating (Katz, Ford, Moskowitz, Jackson, & Jaffe, 1963). Instrumental ADLs (IADLs) involve more cognitively demanding tasks, such as managing money or medication (Lawton & Brody, 1979). Previous research has demonstrated a relationship between accuracy of selfreported functional ability and level of cognitive impairment in nondemented community-based older adults (Mitchell & Miller, 2008a) but has not evaluated that relationship directly against informant report relationships and cognition. This emphasizes the need for accurate report of functional status to attain associative validity. A roadblock to accuracy in reporting involves potential bias within reports of functional status. Although obtaining self-report remains an important factor in identifying functional limitations (Elam et al., 1991), older adults may not selfreport such problems to a physician or other health professional. Researchers have found that older adults frequently overestimate their functional abilities. This could be a result of denying difficulties as a coping mechanism, a desire to not appear as a burden to others, or a misperception of current abilities (Rubenstein et al., 1984). However, caregiver reports of functional status may also have inaccuracies. Cotter, Burgio, Stevens, Roth, and Gitlin (2002) examined the correlation between caregiver report of assistance with ADL tasks and behavioral observation of this assistance within the home. Caregivers were found to be accurate reporters of the nature of assistance when compared with behavioral observation, although they tended to overestimate the amount of time it took to provide assistance to older
Downloaded from jag.sagepub.com at GEORGIAN COURT UNIV on May 10, 2015
5
Miller et al.
adults. Other researchers have shown caregivers to report more pervasive exaggerations of older adult functional deficits, perhaps as a result of caregiver burden (Rubenstein et al., 1984). Some researchers have shown no effect of variables such as relationship of caregiver to older adult or amount of caregiver time spent with an older adult as related to the discrepancy between caregiver and self-report (Farias, Mungas, & Jagust, 2005). Others have shown that live-in spouse caregivers are associated with higher ratings of accuracy (Ready, Ott, & Grace, 2004). Such potential biases make the relationship between caregiver reports and objectively measured indices of older adult function more complex. Accuracy of caregiver report has been related to decrements in older adult functional and cognitive domains. A study contrasting caregiver-reported ADLs and behaviorally observed ADLs in older adults exhibited strong correlations in the domain of motor functioning (walking) and moderately strong correlations in other basic activities (dressing). Correlations were weaker for IADLs, such as managing money (Zanetti, Geroldi, Frisoni, Bianchetti, & Trabucchi, 1999). Studies focusing on IADLs have similarly shown weak accuracy of self- and informant reports of financial abilities, consistent older adult overestimation of skills, and low stability of both types of reports (Wadley, Harrell, & Marson, 2003). Research reporting changes in cognitive status suggest that older adult decrements in memory predict a self-report–caregiver report discrepancy (Farias et al., 2005). A growing literature has investigated the association between cognitive deficit and functional status. Dodge et al. (2005) estimated that cognition accounted for 18% to 36% loss in BADL abilities and 11% to 29% of loss in IADL abilities in a community-based sample of older adults. Longitudinally, cognitive impairment at baseline in participants experiencing no functional decrement was a risk factor for later decline (1 year post baseline) in BADLs and IADLs (Dodge et al., 2005). Bennett et al. (2006) suggested global cognitive functioning accounted for up to 22% of the variance in functional status, particularly within the domain of housework but found no specific cognitive domain that was uniquely related to functional status. However, several studies suggest that executive functioning plays a significant role in facilitating activities of daily living (Grigsby, Kaye, Baxter, Shetterly, & Hamman, 1998; Lewis & Miller, 2007; Mitchell & Miller, 2008a, 2008b). After controlling for demographic factors, Johnson and colleagues found that decrements in executive functioning, as measured by the Trails B test, were predictive of later decline in ADLs in female older adults (Johnson, Lui, & Yaffe, 2007). Others suggest that cognitive and physical processes independently contribute to an individual’s ability to complete ADLs (Gill, Williams, Richardson, & Tinetti, 1996; Petrella, Cress, & Miller, 2004).
Downloaded from jag.sagepub.com at GEORGIAN COURT UNIV on May 10, 2015
6
Journal of Applied Gerontology 32(1)
The current investigation sought to examine caregiver versus self-report of functional status and their relationship to objective measures of cognitive function. In the current investigation, we compared caregiver and self reports of BADLs and IADLs as they relate to measures of cognition in older adults. Discrepancies within the current literature associating the role of caregiver and self-report with older adult cognition are difficult to reconcile due to variability in methodology and sample size across studies. To account for such issues, we used two samples of community-based dyads, with both older adult and caregiver in each sample completing nearly identical functional report measures. Another aim of the current study was to use a large sample size of caregiver– older adult dyads and specifically employ common clinical measures of cognition to evaluate the relationship between reported functional status and cognition. We used the Cognistat: Neurobehavioral Cognitive Status Examination (Cognistat; Northern California Neurobehavioral Group, Inc., 1995; Kiernan, Mueller, Langston, & Van Dyke, 1987) and the Repeatable Battery for the Assessment of Neuro psychological Status (RBANS; Randolph, 1998) to compare the correlation of functional measures with neuropsychological measures commonly used in geriatric populations. We sought to identify the relationship between older adult cognitive status and reported functional status and also to examine what domains of cognition may hold the most associative power in caregiver report of older adult functional status. Domains of cognitive function associated with caregiver reports on older adult functional impairment would be helpful for clinicians to clarify what aspects of cognitive decline may be most readily observed when assessing older adult functional status by self- and collateral report. Based on the extant literature, we hypothesized that (a) caregiver reports of older adult total ADLs would be more highly associated with older adult cognition than self-reports of total ADLs; (b) caregiver reports of older adult BADLs and IADLs would each be more strongly associated with cognition than selfreport; and (c) IADLs would be more highly associated with cognition than BADLs, regardless of report method. In testing the above hypotheses, we separately analyzed data from two different studies. In Study 1, participants were drawn from the Family Relationships in Late Life (FRILL) study (described below), in which the Cognistat was used as a measure of older adult cognition. In Study 2, participants included caregiver– older adult dyads from the second FRILL study (FRILL2), including an oversampled set of African American dyads. In Study 2, the RBANS was used as a measure of older adult cognition. Furthermore, in identifying an associative relationship between caregiver reports of older adult total ADL and older adult RBANS scores, we sought to
Downloaded from jag.sagepub.com at GEORGIAN COURT UNIV on May 10, 2015
7
Miller et al.
isolate specific domains of cognitive function that could drive this relationship. In Study 2, we expanded our comparison of BADLs and IADLs tested in Study 1 by also examining specific domains of cognitive functioning as they relate to the maintenance of daily functioning. We were interested in whether the relationship between cognitive functioning and both BADLs and IADLs tested within Study 1 were being driven by particular cognitive processes. Specifically, we were interested in determining which components of cognition were essential for the maintenance of simple versus complex activities of daily living (i.e., BADLs vs. IADLs). To accomplish this goal, we reversed associated variables to directly compare the variance in functional status (caregiver reported older adult BADL and IADL) accounted for by five RBANS index scores. We hypothesized that (a) the older adult performance on RBANS indices of visuospatial and attentional tasks would be most highly associated with BADL decrements because these fundamental activities (e.g., dressing, grooming, bathing) require visuomotor coordination, speed, and spatial navigation. In contrast, we hypothesized that (b) older adult performance on RBANS indices of language and delayed memory would be the most highly associated with IADL decrements because these more complex activities (e.g., managing finances, managing medications, grocery shopping) require higher order cognitive abilities such as naming ability, verbal fluency, and memory functioning. In addition, language and delayed memory functioning are most likely to decline in preclinical Alzheimer’s disease (Randolph, 1998) and decrements in these domains may be more likely in individuals experiencing functional decline in IADLs. We chose to use caregiver report of older adult ADL functioning because Study 1 findings suggested that caregiver ratings of older adult functional status were more sensitive (i.e., larger range in scores and higher mean rating of functional decrements).
Study 1 Method Sample and Procedures. In Study 1, participants were drawn from the FRILL study of informal caregiver–older adult dyads, recruited from three recruitment sites: Athens, Georgia; Pittsburgh, Pennsylvania; and Dallas, Texas. Caregivers were defined as those who provided unpaid assistance with at least two IADLs (e.g., managing money) or one BADL (e.g., bathing) to community-dwelling adults aged 60 years or older. The source of older adult impairment was not a factor in participant selection. Details of the FRILL protocol have been reported elsewhere (Beach et al., 2005; Miller et al., 2006).
Downloaded from jag.sagepub.com at GEORGIAN COURT UNIV on May 10, 2015
8
Journal of Applied Gerontology 32(1)
The FRILL project was approved by all necessary institutional review boards. Participants were screened by telephone for eligibility and then interviewed in person within their homes. Caregivers and care recipients were interviewed concordantly and separately to prevent data contamination. Research staff were properly trained on interview procedures and assessment administration. Each individual received US$20 for their participation. Testing lasted 1.5 to 2 hr per participant. Recruitment efforts yielded a total of 283 dyads. Because of the extremely small number of dyads being neither White nor African American (4 dyads in “Other” category), we excluded those dyads, creating a dichotomous category for older adult race (n = 279, coded as 1 = White, 2 = African American). Of the 279 remaining dyads, 41 were excluded from analyses due to missing data on the primary measures of interest (older adult demographics; caregiver and self reports of BADLs and IADLs; older adult composite Cognistat score) leaving 238 dyads.
Measures Older adult cognitive status. Older adults completed the Cognistat (Northern California Neurobehavioral Group, Inc., 1995), which examines general cognitive functioning in 10 domains (orientation, attention, language comprehension, memory, design construction, language repetition, naming, calculations, reasoning, and judgment) and has been shown to have good sensitivity in distinguishing cognitively impaired adults in older adults (Drane & Osato, 1997). Due to limited sample sizes in published normative data for the Cognistat, we followed Miller and colleagues’ (2006) impairment rating procedure to create a composite severity score for each participant. A rating scale of 1 to 4 was created for each domain, with 1 representing lack of impairment, and 4 representing severe impairment in a given area. The summed composite rating for each individual domain was used as an estimate of older adult cognitive functioning (range = 10-40). Older adult and caregiver reported amount of help provided. Both the caregiver and older adult completed an 18-item assessment, adapted from the ADL instrument (Older American Resources and Services, Duke University, 1978) to assess older adult level of functional status. The older adult’s performance of BADLs and IADLs were based on a metric of 0 to 5. Activities that older adults had never participated in were rated 0 (e.g., if an older adult had not participated in managing couple’s money prior to impairment), to differentiate preimpairment delegated activities from level of postimpairment assistance. Activities that older adults had engaged in preimpairment received a rating between 1 and 5: A score of 1 on the scale represented activities which the older adult completed with no help, whereas a 5 represented an activity requiring a great deal of help by the caregiver. Total ADL scores have a theoretical range of 0 to 90, BADLs range
Downloaded from jag.sagepub.com at GEORGIAN COURT UNIV on May 10, 2015
9
Miller et al.
from 0 to 50, and IADL range from 0 to 40. In addition, discrepancy scores were calculated by subtracting self-rated ADLs from caregiver reported older adult functional status to have a single measure of the relative size differences between caregiver and self-reports of functional status.
Results Sample Description. Mean caregiver age was 62 years (SD = 15, range = 20-88
years), and mean older adult age was 77 years (SD = 8.4, range = 60-98 years). Similar to national estimates (e.g., National Alliance for Caregiving & AARP, 2004), the majority of participants in the caregiver role were female (78%) and either a spouse (48%) or adult child (37%). Education and race for both studies are reported in Table 1. Cognitive and Functional Status. Older adults demonstrated a wide range of abilities in both cognitive domains, based on Cognistat summed composite rating, as well as within functional domains, based on self- and collateral reports of BADLs and IADLs (see Table 1). Bivariate Analysis. Older adult education and race correlated with their Cognistat composite score (r = −.334, p < .001; r = .244, p < .001, respectively), with lower Cognistat scores (higher functioning) seen more frequently in higher educated individuals and in White samples. Caregiver education and ethnic background similarly correlated with older adult Cognistat score (r = −.149, p < .05, and r = .263, p < .001, respectively). Neither older adult nor caregiver gender showed significant correlations with measures of functional status and so were not included in further analyses. Caregiver-reported older adult total ADL correlated positively with older adult Cognistat composite score (r = .296, p .05). Older adult composite Cognistat score was significantly correlated with both self-reported and caregiverreported IADLs (caregiver: r = .404, p < .001; older adult: r = .182, p .05; caregiver IADL: β = .349, t = 5.766, p < .001). To compare the impact of the overall magnitude of differences between caregiver and self-reports of both BADLs and IADLs, we ran a regression analysis using our discrepancy score variable. The discrepancy between caregiver and self-rated BADL scores were significantly associated with older adult cognition, ΔR2 = .03, ΔF(1, 234) = 8.756, p < .01. Interestingly, when the discrepancy between caregiver and self-rated IADL scores were added to the model to identify unique variance accounted for by IADLs above and beyond that accounted for by BADLs, the discrepancy scores of BADL and IADL functioning appeared to share variance. This step did not display significant
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Journal of Applied Gerontology 32(1)
Table 2. Study 1 Regression Analysis for Prediction of Cognistat Composite Score by Older Adult and Caregiver Demographic Variables and Total ADL Measures and Older Adult–Caregiver Total ADL Discrepancy Score Step
β
Variables entered
Total ADL measures 1A Caregiver race .228 Older adult education −.308 Caregiver race .231 1B Older adult education −.299 .056 Self-reported total ADL Caregiver race .200 1C Older adult education −.295 −.127 Self-reported total ADL .320 Caregiver-reported total ADL Caregiver–older adult combined BADL/IADL discrepancy score 2A Caregiver race .228 Older adult education −.308 Caregiver race .201 2B Older adult education −.321 .201 Caregiver–older adult total ADL discrepancy score Step 1A/2A 1B 2B 1C
t
p
3.787 −5.124 3.832 −4.914 0.930 3.428 −5.044 −1.794 4.555
