Executive ability and physical performance in urban Black older adults

Archives of Clinical Neuropsychology 23 (2008) 593–601

Executive ability and physical performance in urban Black older adults Brooke C. Schneider a,b,∗ , Peter A. Lichtenberg a,b a b

Institute of Gerontology, Wayne State University, Detroit, MI, United States Department of Psychology, Wayne State University, Detroit, MI, United States Accepted 5 June 2008

Abstract Executive dysfunction is correlated with disability in tasks of daily living. Less is known about the relationship between cognition, particularly executive dysfunction, and physical performance. This study investigated how executive ability, measured by the Trail Making Test, Part B (TMT-B), Controlled Oral Word Association test (COWA) and Animal Naming (AN), related to completion of physical tasks on the Short Physical Performance Battery (SPPB). The sample included 68 urban-dwelling Black adults ages 59–95. AN and TMT-B accounted for 6.2% and 7.1% of the variance, respectively, in SPPB total score after controlling for general cognitive functioning (Mini Mental Status Exam) and demographics. COWA and the MMSE did not obtain significance. Only the TMT-B remained significant after accounting for illness burden. Findings suggest that executive ability is related to physical performance in older urban Black adults more than general cognitive functioning. This relationship is attenuated by illness burden. © 2008 National Academy of Neuropsychology. Published by Elsevier Ltd. All rights reserved. Keywords: Disability; Executive function; Short Physical Performance Battery; Cognition; Older adults

1. Introduction Disability in activities of daily living relates to cognitive impairment among older adults (Gill, Williams, Richardson, & Tinetti, 1996), particularly executive dysfunction (Royall, Chiodo, & Polk, 2000). Executive ability broadly defines a range of cognitive skills that are involved in the planning, initiation, sequencing and monitoring of complex, goaldirected behavior (Royall et al., 2002). Older adults with executive dysfunction report a greater number of dependencies in instrumental activities of daily living (IADLs). IADLs are defined as the ability to plan, initiate and properly execute cognitively complex tasks of daily living such as balancing a checkbook, performing household tasks and taking medications (Royall et al., 2000). Individuals with combined IADL disability and cognitive dysfunction exhibit greater declines in physical performance over time (Wang, Van Belle, Kukull, & Larson, 2002). While the relationship between executive ability and disability (i.e., IADL impairment) is well established (CahnWeiner, Boyle & Malloy, 2002; Royall et al., 2002) much less is known about how executive dysfunction may be related to an adult’s performance of basic physical tasks, namely walking, chair stands and balance. A significant relationship has been consistently been found between cognitive impairments and physical performance (Atkinson et al., 2007; ∗ Corresponding author at: Institute of Gerontology, Wayne State University, 87 E. Ferry Street, 226 Knapp Building, Detroit, MI 48202, United States. Tel.: +1 313 577 2297; fax: +1 313 875 0127. E-mail address: bc [email protected] (B.C. Schneider).

0887-6177/$ – see front matter © 2008 National Academy of Neuropsychology. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.acn.2008.06.003

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Inzitari et al., 2007); however the nature of this relationship remains unclear. The field of gerontology has identified lower-extremity physical performance measures as key for identification of early changes that may lead to disability in older adults. Neuropsychologists are in a unique position to examine the association between executive ability and measures of physical performance in elder populations in an effort to better understand the pathways toward disability in older adults. Previous studies have shown mixed findings regarding the relationship between intact general cognitive functioning and successful performance of tasks of daily living. Several studies have used screening measures such as the Mini Mental Status Exam (MMSE) to demonstrate a relationship between general mental status and performance of tasks of daily living in normal older adults, as well as those diagnosed with dementia (Boyle, Paul, Moser, & Cohen, 2004; Grigsby, Kaye, Baxter, Shetterly, & Hamman, 1998). While Royall, Palmer, Chiodo, and Polk (2004) found a relationship between MMSE scores and IADLs at baseline, they found no relationship between change in MMSE score and rate of IADL change. More recently, Inzitari et al. (2007) reported a significant relationship between MMSE scores and motor performance; however, when demographic and comorbid disease variables were entered into the model, this relationship was no longer significant. When compared to general cognitive functioning and specific cognitive domains such as memory, language, visuospatial skills and psychomotor speed (Cahn-Weiner, Malloy, Boyle, Marran, & Salloway, 2000; Carlson et al., 1999), executive ability has generally been shown to be most predictive of longitudinal declines in functional status and performance of physical tasks (Cahn-Weiner et al., 2002; Royall et al., 2000). Royall, Palmer, Chiodo, and Polk (2005) reported that executive ability, but not word-list learning, was significantly associated with change in IADL scores. Measures of executive ability have also been shown to predict change in motor performance better than general cognitive functioning and memory (Inzitari et al., 2007). More specifically, within the construct of executive ability, the capacity to plan is significantly associated with functional status (Lewis & Miller, 2007). Physical performance tasks are objective measures of disability that require a high degree of attention, planning and organization. As such, an older adult’s ability to complete physical performance tasks may be related to executive ability. Guralnik, Ferrucci, Simonsick, Salive, and Wallace (1995) studied physical performance in older adults using the Short Physical Performance Battery (SPPB) comprised of three physical performance tasks: chair stands, standing balance and an 8-foot walk. Changes in an older adult’s ability to complete these tasks were predictive of subsequent disability, as measured by mobility impairments and performance of activities of daily living (ADLs). Measures of lower, versus upper, extremity performance may be more predictive of future disability because lowerextremity function has a greater impact on an older adult’s ability to remain independent (Guralnik et al., 1995). As such, the SPPB may be used as a prognostic indicator for older adults who report little or no current disability, as well as those who are experiencing IADL/ADL disability. The SPPB is significantly related to later changes in ADLs, hospitalization and nursing home entry, indicating that declines in physical performance are related to real-world outcomes, namely disability in tasks older adults engage in on a daily basis. Demonstrating a relationship between executive ability and physical performance, in addition to IADLs, would better our understanding of cognitive correlates of early disability in older adults. There are many hypotheses regarding why this relationship between physical performance and executive ability in an elderly population exists. One hypothesis is that regions of the brain responsible for executive ability tasks, primarily the frontal cortex, undergo structural changes through the normal aging process and as sequelae of health conditions and direct injury (Burke & Barnes, 2006). Gait and balance abnormalities, executive dysfunction and deficits in complex attention are symptoms of a variety of late-life disorders, such as dementias. While all individuals are eventually affected by cognitive changes due to aging, these changes occur at different rates and result in variable outcomes. Therefore, it is important to identify cognitive domains most likely to impact functional and physical performance. Few studies examining physical performance or disability have included a substantial sample of older urban Black participants, a population that has consistently been found to report higher levels of disability and a greater number of diseases. Older urban Black adults tend to score more poorly on performance-based measures of physical function than both White adults (Mendes de Leon, Barnes, Bienias, Skarupski, & Evans, 2005) and suburban Blacks (Andresen & Miller, 2005). The specific mechanisms that produce health disparities remain unclear (Williams, 2005). Therefore, when investigating pathways to disability and the mechanisms by which outcome differences occur, it may be most important to examine differences in disability onset among individuals within the same race and ethnic groups. Black/White comparisons may be less illuminating than the examination of various intra-group social and cultural factors that may act as possible sources of risk and resilience for Black elders (Whitfield & Hayward, 2003). Identifying

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how disability risk differs within racial groups as a function of psychosocial, cognitive and demographic factors should improve understanding of pathways to disability. The purpose of this study was to extend the literature on the relationship between objective measures of disability risk and cognitive functioning in a sample of urban Black older adults by addressing two goals. The first goal was to determine whether general cognitive functioning, as measured by the MMSE, was related to a measure of physical performance, as measured by the SPPB. The second goal was to examine the amount of variance in physical performance scores accounted for by executive ability. Based on previous research, it was hypothesized that general cognitive functioning would not be associated with physical performance in this sample while measures of executive ability would be significantly associated with physical performance. 2. Method 2.1. Participants Participants were drawn from the Stress and Success in Aging through Good Health and Executive Ability (SAGE) database. This project received approval from the Institutional Review Board, Human Investigation Committee of Wayne State University. Prior to participation all subjects provided signed consent. Subjects were recruited from independent living centers, community centers, and senior apartments through fliers and by word of mouth. The SAGE database was originally collected for two Master’s theses on topics unrelated to physical performance. The sample included adults between the ages of 59 and 95, who resided in the city of Detroit. Individuals who were unable to speak English fluently were excluded from the study, as were those with major hearing or vision loss as these limitations prohibited their ability to complete the study measures. Because this study investigated the relationship between cognitive functioning and physical performance in all older adults, participants were not excluded based on cognition or general health status. Participants received monetary compensation ($15) for their time. The final sample included 68 urban Black adult participants. Participant education ranged from 5 to 20 years. The majority of the participants were female (78%), all were Black and native English speakers. This sample reflects a slightly greater proportion of females than in the Detroit older adult cohort (Chaplewski, 2002), while education and age are generally consistent with this population. 2.2. Illness burden A modified version of the Charlson Morbidity Index (CMI), based on the classification system developed by Charlson, Pompei, Ales, and MacKenzie (1987), was utilized. It is a weighted index that accounts for the number and severity of comorbid diseases. The CMI assigns weights to each disease reflecting the relative risk for death after controlling for the contribution of all coexistent comorbid diseases, as well as illness severity. The index, as used in this study, was modified to fit the demographic characteristics of the current population as not all conditions included in the original scale were present. Included diseases and their assigned weights used in this study are as follows: myocardial infarct, ulcers, mild liver diseases, lung diseases, stroke, connective tissue diseases (arthritis) and diabetes were assigned a weight of one; moderate or severe renal disease and cancer were assigned a weight of two. Weights for each individual are summed to obtain a final score. These weights were developed in the original validation study in accordance with their relative predictive ability to patient death. All health conditions were obtained via participant self-report. The CMI has been shown to have strong correlations with disability and is predictive of hospitalization (DeGroot, Beckerman, Lankhorst, & Boutler, 2003). 2.3. General cognitive function The Mini Mental Status Exam (MMSE) is an 11-item screening tool used to obtain an estimate of an individual’s global cognitive functioning and orientation to date, time, and place. Scores range from 0 to 30 with higher scores indicating better cognitive functioning. A cut score of 24 is frequently employed below which cognitive impairment is indicated (Crum, Anthony, Basset, & Folstein, 1993).

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2.4. Executive ability Three measures of executive ability were used to assess the various components of the construct of executive ability. These measures were chosen because they were part of the Mayo Older African American Normative Studies (MOAANS) and have been validated in samples of older Black adults (Lucas et al., 2005). The Trail Making Test (TMT; Reitan & Wolfson, 1985) is a timed test of complex sequencing abilities and setshifting. The test is comprised of two parts. In the first, Part A, participants are asked to connect numbers in numerical order (1-2-3 and so on) as quickly as possible. In the second section, Part B (TMT-B), participants connect letters and numbers in a sequential alternating pattern (i.e., 1-A–2-B and so on) as quickly as possible. Scores are based on the time to completion. The TMT has been shown to be a sensitive indicator of executive ability and motor speed. Extensive reliability and validity testing has been done on the TMT. Reliability coefficients for Part B are generally about .67 while interrater reliability is quite high, at .90, for Part B (Lezak, 1995). The TMT-B is related to both current and future IADL functioning in older adults (Cahn-Weiner et al., 2002; Carlson et al., 1999). The Controlled Oral Word Association Task (COWAT; Benton & Hamsher, 1976) and Animal Naming (AN) are measures of verbal fluency that involve rapidly naming items that fit a description provided by the administrator. Patients are asked to generate as many words as possible beginning with the letters F, A, and S, as well as animal names, in 1-min interval. The total score for each test equals the number of correct words generated by the participant. Perseverations and incorrect answers were not counted. Upon retesting of older adults after 1 year, the letters “F”, “A” and “S” have reliability coefficients of .70, .60 and .71, respectively (Snow, Tierney, Zorzitto, Fisher, & Reid, 1988). Overall test-retest reliability has been shown to be .74 (Ruff, Light, Parker, & Levin, 1996). 2.5. Disability risk The SPPB used in this study was based on methodology used in the Established Populations for Epidemiologic Studies of the Elderly (EPESE) studies that examined physical functioning in over 5000 older, mostly White adults (Guralnik et al., 1994). Lower-extremity function was assessed through the performance of three tasks: standing balance, walking, and chair stands. Balance was measured by the amount of time each participant could maintain each of the following three poses: semi-tandem (heel of one foot to the side of the first toe of the other foot), tandem (heel to toe) and side-by-side. Timing stopped when the participant lost balance, grasped for the examiner or 10 s had elapsed. Using criteria from Guralnik et al. (1994), participants received a score of a 1 if they were able to hold a side-by-side position for 10 s, but were unable to hold a semi-tandem position; a score of a 2 if they could hold a semi-tandem position for 10 s but were unable to hold a full tandem for more than 2 s; a score of a 3 if they could stand in full tandem for 3–9 s; and a score of a 4 if they could stand in full tandem for 10 s. Gait speed was assessed by two 8-foot walks, at a normal everyday pace, that was marked out for each subject in advance. The faster of their two walks was used as their final score further divided into quartiles such that a score of 1 = ≥5.7 s (≤0.43 m/s); a score of 2 = 4.1–5.6 s (0.44–0.60 m/s); a score of 3 = 3.2–4.0 s (0.61–0.77 m/s); and a score of 4 = ≤3.1 s (≥0.78 m/s). The final task, chair stands, required the participants to sit up and down with their arms across their chest five times as quickly as they could. Times were then recorded into quartiles such that a score of a 1 = ≥16.7 s; a score of a 2 = 13.7–16.6 s; a score of a 3 = 11.2–13.6 s; and a score of a 4 = ≤11.1 s. Quartile scores for each subtask (standing balance, gait speed, and chair rises) were summed to yield a summary performance score. Guralnik et al. (1994) obtained a reliability estimate of .76 for the scale and categorical scores were significantly correlated at p < .001 (walking and chair stands = .48; walking and standing balance = .39; chair stands and standing balance = .39). In the SAGE dataset, all subtask scores were also significantly correlated at p < .001 (walking and chair stands = .64, walking and standing balance = .63, and chair stands and standing balance = .47). 2.6. Procedure This study used data from a larger data collection effort that included measures of religious beliefs, stressors, mood and perceived social support. To minimize participation restrictions due to transportation limitations, participants were

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met at care facilities, community centers, senior apartments and other locations near their place of residence. After participants were recruited, each was administered the previously mentioned battery of tests. Each participant was administered a battery of measures in a single session. The battery was no less than 2 h and often longer for those who were slow. Nine participants received scores of 5 (a commonly accepted cutoff) or more on the 15-item Geriatric Depression Scale (GDS-15; Sheikh & Yesavage, 1986). T-test comparisons were conducted to examine differences between depressed and non-depressed individuals on measures of cognitive functioning and physical performance. A significant difference was found between groups for SPPB score. To detect the possible effects of depression on the relationship between cognitive functioning and physical performance, all analyses were rerun excluding these individuals. No differences were found regarding the significance of variables, thus all participants were included in the analyses regardless of reported level of depression. Prior to conducting the analyses, all variables were screened for violations of the assumptions of multivariate normality and corrected. To examine the relationship between the SPPB, general cognitive functioning and executive ability, point biserial and bivariate correlations were obtained between all predictor variables and the SPPB. A series of three hierarchical regression analyses, one for each executive ability measure, were conducted to test for significant relationships between measures of executive ability and SPPB. SPPB summary score was the dependent variable for each individual regression. Age, education, gender and MMSE were entered into Block 1. Executive ability measure was entered in Block 2 for each hierarchical regression. CMI was entered in Block 3. This design permitted an examination of the effect of executive ability after the effects of age, education, gender and general cognitive functioning had already been taken into account for Block 2. Block 3 elucidates the impact of disease burden on the relationship between executive ability and physical performance. A final multiple regression was conducted to examine the relative importance of each variable when entered simultaneously in the model. 3. Results Characteristics of the overall sample and their test results are reported in Table 1. All predictor and outcome variables were transformed to z-scores to detect outliers, defined as data points greater than three standard deviations from the mean. Based on this screening procedure, no outliers were detected. TMT-B was significantly skewed. As suggested by Tabachnik and Fidell (2001) a logarithmic transformation was used to reduce significant kurtosis of TMT-B scores. The transformed scores were again screened and met multivariate normality criteria. Transformed scores were used in all analyses. The relationship between the SPPB, demographic variables (i.e., age, gender, education), general cognitive functioning (MMSE), executive ability measures, and illness burden (CMI) were initially examined with bivariate and point biserial (for gender only) correlations using a listwise deletion. A p-value of ≤.05 was considered significant. Table 2 presents a correlation matrix of the variables. Using the hierarchical regression analyses with listwise deletions, R2 change values were significant at Block 1. The MMSE was not significantly associated with SPPB when entered simultaneously with age, gender, and education. Age Table 1 Descriptive statistics of sample characteristics Mean (overall N = 68) Age Education Gender SPPB CMI MMSE TMT-B COWAT AN

73.21 12.49 (78% female) 6.32 1.36 25.59 198.26 26.63 13.55

S.D. 8.17 3.21 3.32 1.33 2.84 82.33 11.35 4.59

Range 59–95 5–20 0–12 0–5 18–30 57.53–300 9–54 40–25

Note: Abbreviations in this table are as follows: SPPB = Short Physical Performance Battery; CMI = Charlson Morbidity Index; MMSE = Mini Mental Status Exam; TMT-B = Trail Making Test, Part B time; AN = Animal Naming; COWA = Controlled Oral Word Association test.

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Table 2 Descriptive correlations among predictor variables and physical performance

Age Gender Education SPPB CMI MMSE TMT-B AN COWA

Age

Gender

– −.02 −.06 −.33* −.12 −.42* .33* −.53* −.26*

– −.07 .21 .05 −.22 −.02 .01 .08

Education

SPPB

CMI

MMSE

TMT-B

AN

– −.60* .48* .42*

– −.52* −.54*

–

COWA

– .13 .05 .33* −.32* .15 .28*

– −.40* .22 −.41* .42* .35*

– .00 .06 −.21 .09

.51*

–

Note: Abbreviations in this table are as follows: SPPB = Short Physical Performance Battery; CMI = Charlson Morbidity Index; MMSE = Mini Mental Status Exam; TMT-B = Trail Making Test, Part B; AN = Animal Naming; COWA = Controlled Oral Word Association test. *p < .05. Table 3 Block 1: Short Physical Performance Battery scores by demographic variables and MMSE Variables

Beta

SE B

β

sr2

Age Gender Education MMSE

−.10 1.90 .09 .16

.05 .94 .13 .16

−.26 .24 .08 .14

.05* .05* .00 .01

Note: Block 1: R = .42, R2 = .17, Adj R2 = .12, Std. Err. of Est. = 3.11, F = 3.32 (4, 63), p < .02. MMSE = Mini-Mental Status Exam. *Significant at p < .05.

and gender were significant predictors of SPPB scores (p < .05). Block 1 accounted for 17% of the variance in SPPB scores (p < .02). Summary statistics for Block 1 are included in Table 3. R2 change values were significant in Block 2 for TMT-B and AN in their separate hierarchical regression analyses, indicating that executive ability accounted for further variance in the SPPB. TMT-B accounted for an additional 7.2% (p < .05) and AN accounted for 6.1% of the variance (p < .05). COWAT (p = .06) approached significance. In Block 2, the executive ability measures were the only significant predictor of SPPB scores; age and gender were no longer significant. After the addition of CMI to each hierarchical regression in Block 3, AN (p = .26) became nonsignificant while TMT-B remained significant (p = .02). CMI was significant in analyses for each executive ability measure. Summary statistics for Block 2 and Block 3 are included in Table 4. Finally, a multiple regression analysis was conducted to ascertain the relative importance of all variables (i.e., gender, age, education, MMSE, TMT-B, AN, COWAT, and CMI) in the model, but primarily to examine the contributions of executive ability scores. When entered into the model simultaneously, age (p < .05) and CMI were significant (p < .01). None of the cognitive variables were significant. Null findings may result from the commonality between the executive ability measures administered. AN, TMT-B and COWAT are relatively highly correlated because they are all speeded measures of executive ability, and as a result share a large amount of variance in common. It is thought that this shared Table 4 Contribution of executive ability to Short Physical Performance Battery scores Test

TMT-B AN COWAT

Block 2

Block 3

Beta

SE B

β

p

R2

Beta

SE B

β

p

−5.73 .23 .07

2.36 .10 .04

−.35 .31 .25

.02 .03 .06

.07 .06 .05

−5.00 .11 .06

2.13 .10 .03

−.30 .15 .20

.02 .26 .09

Note: Results are based on separate reduced and full hierarchical regression models for each cognitive test. Block 2 adjusted for age, gender, education and MMSE score. Block 3 also adjusted for Charlson Morbidity Index (CMI). TMT-B = Trail Making Test, Part B; AN = Animal Naming; COWA = Controlled Oral Word Association test.

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variance may block the ability of any one test to obtain significance when all executive ability measures are entered simultaneously. This null finding is discussed further below. This final analysis also underscores the impact of illness burden on physical performance. 4. Discussion Study results provide support for the hypothesis that executive ability is associated with the SPPB, a measure of physical performance and an indicator of disability risk, in older urban Black adults. Two of the three executive ability measures used (TMT-B and AN), were significantly related to physical performance after accounting for demographics and general cognitive functioning. A trend toward significance was found for the third measure (COWAT). After the addition of disease burden (CMI) the relationship between AN and SPPB became nonsignificant, while TMTB remained a significant predictor of SPPB performance. These results provide further evidence of the relationship between executive ability and physical performance. Implications for the assessment of disability risk in older Black adults will be discussed. The MMSE was not significantly related to SPPB scores within the present sample of urban Black older adults. This finding corroborates results from Inzitari et al. (2007), but contrasts findings from studies by Malmstrom, Wolinksy, Andresen, Miller, & Miller (2005) and Atkinson et al. (2007). The discrepancy in findings may be a result of test characteristics of alternative versions of the MMSE. For example, the Modified Mini Mental Status Examination (3MS; Atkinson et al., 2007), taps a wider range of cognitive skills than the MMSE and is thought to be less biased by age and education (Cullen, O’Neill, Evans, Coen, & Lawlor, 2007). Additionally, in the Malmstrom et al. (2005) study, MMSE scores were divided into quartiles rather than analyzed as continuous variables. Given that their sample was middle-aged, it is likely that MMSE scores were skewed, thus necessitating a different analytical approach. Despite differences in methodology and results, taken together, our findings suggest that the MMSE alone may not be a good indicator of disability risk in older Black adults. Though the TMT-B and AN were significant predictors when entered independently, they became nonsignificant when entered simultaneously into the regression. As discussed previously, both AN and TMT-B are measures of executive ability and, as such, they are highly correlated (r = −.52) and share predictive variance in this final analysis. These results do provide useful information. Because the TMT-B requires psychomotor integration and visuomotor speed, as do physical performance tasks, we questioned whether the psychomotor factor may account for its relationship with the SPPB. However, AN, a timed measure of verbal fluency and executive ability, was also significantly related to the SPPB. It may be concluded that since TMT-B and AN prohibit each other from attaining significance when entered into the model simultaneously, they share common variance attributable to speeded processing and executive ability. The null results, in conjunction with the significance of AN and TMT-B when entered alone, support the conclusion that the executive ability component of TMT-B contributes to its association with the SPPB. While the executive ability tests accounted for a small portion of overall variance in the model, 7.1% and 6.2%, respectively, this is indicative of a small to medium effect size (Cohen, Cohen, West, & Aiken, 2003). Additionally, the final model demonstrated in Block 3 accounted for approximately 37% of the variance in SPPB scores, which indicates a large effect (Cohen et al.). As such, these results do contribute to an overall understanding of the relationship between physical performance, an indicator of preclinical disability, and cognition. This study contributes to the growing literature on the relationship between physical performance and cognitive functioning in minority samples. Our results suggest, and agree with previous studies, that executive ability accounts for unique variance in physical performance scores (Atkinson et al., 2007; Inzitari et al., 2007; Malmstrom et al., 2005). It may be that successful performance of physical tasks, such as gait speed and standing balance, require aspects of executive ability such as concentration, attention and planning. Alternatively, completion of these tasks may involve shared pathways and, thus, pathologies in this pathway would affect performance of both physical tasks and executive ability (Atkinson et al., 2007). Previous studies have included Black participants, yet few have drawn from an urban Black population. The current study is unique in that urban-dwelling Black elders were recruited using minimum exclusion criteria likely resulting in a sample of urban Black participants with various health and psychosocial conditions reflecting actual prevalence rates. Our results suggest that illness burden is a significant predictor of physical performance in urban Black older adults. Given the minimum exclusion criteria, these results may be more generalizable to urban Black adults presenting for treatment in community medical and mental health settings. Excluding participants based on strict standards of

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health and cognitive functioning may result in recruitment of Black elders who are exceptionally high functioning and healthy, thus limiting the generalizability of results (Lucas et al., 2005). Weaknesses of this study include a relatively small sample size (N = 68). This study should be considered exploratory in nature and further work is needed to extend and support the present findings. Despite this small sample size, demographic data was shown to match that of a much larger sample of elder Blacks residing in the city of Detroit (Chaplewski, 2002). Next, the MMSE can be utilized as only a rough estimate of cognitive functioning and was not shown to be related to physical performance in this sample of older urban Black adults. The MMSE is highly correlated with age, education and race; thus, more rigorous measures of general cognitive ability (i.e., WAIS-IV) should be used in future studies. Though depression did not significantly affect the present results, future work should investigate the effects of depression on the relationship between cognitive functioning and physical performance. This study would be improved by incorporating measures that require planning, such as the Wisconsin Card Sorting test or the Tower of London test. It is likely that executive ability measures that are not as dependent on speeded processing would account for a unique proportion of variance beyond TMT-B and AN. Providing such concurrent evidence would further support the relationship between executive ability and physical performance. Finally, neuroimaging studies are needed to corroborate the relationship between executive ability, prefrontal cortex functioning and physical performance. These results extend our knowledge of correlates of predisability by supporting the hypothesis that executive ability is related to physical performance in urban Black adults. Further research is needed to better understand the relationship between executive ability and physical performance, as well as trajectories of disability, with a long-term goal of developing strategies that can be implemented at the earliest stage of intervention to effectively delay disability onset.

References Andresen, E., & Miller, D. (2005). The future (history) of socioeconomic measurement and implications for improving health outcomes among African Americans. Journals of Gerontology: Medical Sciences, 60, 1345–1350. Atkinson, H. H., Rosano, C., Simonsick, E. M., Williamson, J. D., Davis, C., Ambrosius, W. T., et al. (2007). Cognitive function, gait speed decline and comorbidities: The health, aging and body composition study. Journals of Gerontology: Medical Sciences, 62, 844–850. Benton, A. L., & Hamsher, K. (1976). Multilingual aphasia examination. Iowa City: University of Iowa. Boyle, P. A., Paul, R., Moser, D., & Cohen, R. A. (2004). Executive impairments predict functional declines in vascular dementia. The Clinical Neuropsychologist, 1, 214–221. Burke, S. N., & Barnes, C. A. (2006). Neural plasticity in the ageing brain Nature Reviews. Neuroscience, 7, 30–40. Cahn-Weiner, D. A., Boyle, P. A., & Malloy, P. F. (2002). Tests of executive ability predict instrumental activities of daily living in community-dwelling older individuals. Applied Neuropsychology, 9(3), 187–191. Cahn-Weiner, D. A., Malloy, P. F., Boyle, P. A., Marran, M., & Salloway, S. (2000). Prediction of functional status from neuropsychological tests in community-dwelling elderly individuals. The Clinical Neuropsychologist, 14, 187–195. Carlson, M. C., Fried, L. P., Xue, Q., Bandeen-Roche, K., Zeger, S. L., & Brandt, J. (1999). Association between executive attention and physical functional performance in community-dwelling older women. Journal of Gerontology, 54B, S262–S270. Chaplewski, E. (2002). Facing the future: City of Detroit needs assessment of older adults. Detroit, MI: Department of Senior Citizens. Charlson, M. E., Pompei, P., Ales, K. L., & MacKenzie, C. R. (1987). A new method of classifying prognostic comorbidity in longitudinal studies: Development and validation. Journal of Chronic Diseases, 40(5), 373–383. Cohen, J., Cohen, P., West, S. G., & Aiken, L. S. (2003). Applied Multiple Regression/Correlation Analyses for the Social Sciences (3rd ed.). Mahwah New Jersey: Lawrence Erlbaum Associates. Crum, R., Anthony, J., Basset, S., & Folstein, M. (1993). Population based norms for the Mini-Mental Status Examination by age and educational level. JAMA, 269, 2386–2391. Cullen, B., O’Neill, B., Evans, J. J., Coen, R. F., & Lawlor, B. A. (2007). A review of screening tests for cognitive impairment. Journal of Neurology Neurosurgery & Psychiatry, 78, 790–799. DeGroot, V., Beckerman, H., Lankhorst, G., & Boutler, L. M. (2003). How to measure comorbidity: A critical review of available methods. Journal of Clinical Epidemiology, 56, 221–229. Gill, T. M., Williams, C. S., Richardson, E. D., & Tinetti, M. E. (1996). Impairments in physical performance and cognitive status as predisposing factors for functional dependence among nondisabled older persons. Journals of Gerontology: Series A: Biological Sciences and Medical Sciences Special Issue: Series A: Biological Sciences and Medical Sciences, 51A(6), M283–M288. Grigsby, J., Kaye, K., Baxter, J., Shetterly, S. M., & Hamman, R. F. (1998). Executive cognitive abilities and functional status among communitydwelling older persons in the San Luis Valley Health and Aging Study. Journal of the American Geriatrics Society, 46, 590–596. Guralnik, J. M., Simonsick, E. M., Ferrucci, L., Glynn, R. J., Berkman, L. F., Blazer, D. G., et al. (1994). A short physical performance battery assessing lower extremity function: Association with self-reported disability, prediction of mortality and nursing home admission. Journal of Gerontology, 49(2), M85–M94.

B.C. Schneider, P.A. Lichtenberg / Archives of Clinical Neuropsychology 23 (2008) 593–601

601

Guralnik, J. M., Ferrucci, L., Simonsick, E. M., Salive, M. E., & Wallace, R. B. (1995). Lower-extremity function in persons over the age of 70 years as a predictor of subsequent disability. The New England Journal of Medicine, 332(9), 556–561. Inzitari, M., Baldereschi, M., DiCarlo, A., Di Bari, M., Marchionni, N., Scafato, E., et al. (2007). Impaired attention predicts motor performance decline in older community-dwellers with normal baseline mobility: Results from the Italian Longitudinal Study on Aging (ILSA). Journals of Gerontology, 62A, 837–843. Lewis, M. S., & Miller, L. S. (2007). Executive control functioning and functional ability in older adults. The Clinical Neuropsychologist, 21, 274–285. Lezak, M. (1995). Neuropsychological assessment (3rd ed.). New York: Oxford University Press. Lucas, J. A., Ivnik, R. J., Willis, F. B., Ferman, T. J., Smith, G. E., Parfit, F. C., et al. (2005). Mayo’s older African American normative studies: Normative data for commonly used clinical neuropsychological measures. Clinical Neuropsychologist, 19, 162–183. Malmstrom, T., Wolinksy, F., Andresen, E., Miller, J., & Miller, D. (2005). Cognitive ability and physical performance in middle-aged African Americans. Journal of the American Geriatrics Society, 53, 997–1001. Mendes de Leon, C. F., Barnes, L. L., Bienias, J. L., Skarupski, K. A., & Evans, D. A. (2005). Racial disparities in disability: Recent evidence from self-reported and performance-based disability measures in population-based study of older adults. Journals of Gerontology, Series B: Psychological Sciences and Social Sciences, 60, S263–S271. Reitan, R. M., & Wolfson, D. (1985). Category test and trail making test as measures of frontal lobe functions. Clinical Neuropsychologist, 9(1), 50–56. Royall, D. R., Chiodo, L. K., & Polk, M. J. (2000). Correlates of disability among elderly retirees with “subclinical” cognitive impairment. Journals of Gerontology, 55A(9), M541–M546. Royall, D. R., Lauterbach, E. C., Cummings, J. L., Reeve, A., Rummans, T. A., Kaufer, D. I., et al. (2002). Executive control function: A review of its promise and challenges to clinical research. A report from the Committee on Research of the American Neuropsychiatric Association. Journal of Neuropsychiatry and Clinical Neuroscience, 14, 377–405. Royall, D. R., Palmer, R., Chiodo, L. K., & Polk, M. J. (2004). Declining executive control in normal aging predicts change in functional status: The Freedom House study. Journal of the American Geriatrics Society, 52, 346–352. Royall, D. R., Palmer, R., Chiodo, L. K., & Polk, M. J. (2005). Executive control mediates memory’s association with change in Instrumental Activities of Daily Living: The Freedom House Study. Journal of the American Geriatrics Society, 53, 11–17. Ruff, R. M., Light, R. H., Parker, S. B., & Levin, H. S. (1996). Benton Controlled Oral Word Association Test: Reliability and updated norms. Archives of Clinical Neuropsychology, 4, 329–338. Sheikh, J. I., & Yesavage, J. A. (1986). Geriatric Depression Scale (GDS): Recent evidence and development of a shorter version. In T. L. Brink (Ed.), Clinical Gerontology: A guide to assessment and intervention (pp. 165–173). NY: The Haworth Press. Snow, W. G., Tierney, M. C., Zorzitto, M. L., Fisher, R. H., & Reid, D. W. (1988). One-year test-retest reliability of selected tests in older adults. Paper presented at the Meeting of the International Neuropsychological Society. New Orleans. Tabachnik, B., & Fidell, T. (2001). Using multivariate statistics. NJ: Pearson Allyn & Bacon. Wang, L., Van Belle, G., Kukull, W., & Larson, E. (2002). Predictors of functional change: A longitudinal study of nondemented people aged 65 and older. Journal of the American Geriatrics Society, 50(9), 1525–1534. Whitfield, K. E., & Hayward, M. (2003). The landscape of health disparities among older adults. Public Policy and Aging Report, 13(3), 1–7. Williams, D. R. (2005). The health of U.S. racial and ethnic populations. Journal of Gerontology: Social Sciences, 60B(Special Issue II), 53–62.