Journal of Gerontological Nursing

Feature Article 

The Relationship Between Cognitive and Physical Function in Older Adults with Rheumatoid Arthritis: A Literature Review

So Young Shin, PhD, RN, GCNS-BC

Abstract

Intact cognitive function is a crucial underpinning for the performance of daily activities in people with chronic diseases, including rheumatoid arthritis (RA). Older adults with RA may have the increased burden of physical function difficulties due to the impact of both age-related cognitive decline and RA-related impairment. Population-based studies reviewed in this article found significant cross-sectional and longitudinal relationships between cognitive function and physical function in older adults with and without comorbid health conditions. Although no study specifically examined this relationship in older adults with RA, interventions designed to enhance functional capacity by minimizing cognitive impairment may benefit older adults with RA. More studies are needed that investigate the relationship between cognitive and physical function in older adults with RA to eventually improve functional status and quality of life.

Abstract

Intact cognitive function is a crucial underpinning for the performance of daily activities in people with chronic diseases, including rheumatoid arthritis (RA). Older adults with RA may have the increased burden of physical function difficulties due to the impact of both age-related cognitive decline and RA-related impairment. Population-based studies reviewed in this article found significant cross-sectional and longitudinal relationships between cognitive function and physical function in older adults with and without comorbid health conditions. Although no study specifically examined this relationship in older adults with RA, interventions designed to enhance functional capacity by minimizing cognitive impairment may benefit older adults with RA. More studies are needed that investigate the relationship between cognitive and physical function in older adults with RA to eventually improve functional status and quality of life.

Rheumatoid arthritis (RA) is a systemic inflammatory autoimmune disease characterized by pain, joint stiffness, joint swelling, and subsequent functional limitations and disability (Taibi & Bourguignon, 2003). The proportion of older adults living with RA has increased over time due to longevity and disease chronicity (Hootman & Helmick, 2006). Therefore, adverse outcomes in older adults with RA, such as decreased functional status, increased health care costs, increased morbidity and mortality, and decreased psychological well-being, can be anticipated (Helmick et al., 2008). To minimize these outcomes, an understanding of the risk factors that aggravate functional limitations and disability could form the basis for developing effective and targeted interventions (Dunlop et al., 2005).

Cognitive impairment and disability are relatively common problems that make older adults unable to live independently (Hébert, Brayne, & Spiegelhalter, 1999). People with impaired cognitive function have decreased functional independence, reduced quality of life, and increased risk of mortality (Bennett et al., 2002; Neale, Brayne, & Johnson, 2001). For those with chronic diseases such as RA, intact cognitive function is crucial for performing daily activities, including adhering to medication regimens, planning and initiating activities based on one’s current condition, changing plans if pain unexpectedly worsens, and inhibiting behaviors that aggravate pain or worsen health status (Abeare et al., 2010). However, cognitive function has not been extensively studied in people with RA, although several mechanisms may influence cognitive function in these patients (Appenzeller, Bertolo, & Costallat, 2004).

The relationship between global cognitive function and daily functional status has been well-studied in the general population (Reed, Jagust, & Seab, 1989; Skurla, Rogers, & Sunderland, 1988). Among the various domains of cognitive function, executive function and memory have consistently been found to be associated with everyday function, including performance of activities of daily living (ADLs) and instrumental activities of daily living (IADLs) in older adults (Cahn-Weiner et al., 2007; Tomaszewski Farias et al., 2009). People with greater impairment in executive function and memory had more functional limitations (Cahn-Weiner et al., 2007). Additionally, declines in executive function and memory over time independently contribute to declines in daily function (Tomaszewski Farias et al., 2009).

Older adults with RA may have the increased burden of functional limitations and disability in daily activities due to the effects of both age-related cognitive decline and RA-related impairment. Investigating the relationship between cognitive function and functional limitations and disability in older adults with RA may be useful for designing interventions to prevent further disability, maintain functional independence, and improve quality of life. Therefore, the purpose of this article is to review and critique the literature exploring the relationship between cognitive function and physical function in older adults with RA.

Method

An online literature search was conducted to identify research articles investigating the relationship between cognitive function and physical function in older adults with RA. The PubMed, PsycINFO, and CINAHL databases were searched using the following combinations of terms: cognition, cognitive function, neurocognition, neurocognitive function, executive function, memory, memory disorder, cognitive impairment, cognitive disorder “AND” physical function, physical activity, motor activity, physical function difficulty, disability “AND” arthritis. Search inclusion criteria were articles written in English, with human participants 65 and older.

Review articles, commentaries, and books were excluded. After reading abstracts and reviewing full articles, studies unrelated to the topic were excluded. Specifically, studies that examined participants who already had impaired cognitive function due to neurological disorders, such as dementia or Alzheimer’s disease, or those that exclusively enrolled participants with other types of arthritis, such as osteoarthritis or systemic lupus erythematosus, were excluded. The reference lists of relevant articles were then examined to determine whether they led to other works of interest. A check was made to see if there were duplicates, counting them only once.

Because no study was found that specifically assessed older adults with RA, this article includes 27 population-based studies that examined community-dwelling, non-institutionalized older adults with several comorbid health conditions in addition to arthritis but without neurological disorders and were published within the past 20 years (Figure). The major findings, limitations, and strengths of the reviewed articles will be presented below, followed by the implications for future research and nursing practice.

Selection process of reviewed literature.

Figure. Selection process of reviewed literature.

Review and Critique of the Literature

Twelve research articles were cross-sectional studies, and 15 were prospective, longitudinal, cohort studies with observations over 2 or more years (Table; available online at http://www.healio.com/JGN). The numbers of participants in the reviewed studies ranged from 80 to 7,913, and most were women and White. All but four studies examined adults 65 and older. One study (Appenzeller et al., 2004) had no age restrictions. One study (Kempen & Ormel, 1998) included participants who were 57 and older, and two studies (Grigsby, Kaye, Baxter, Shetterly, & Hamman, 1998; Kuo, Leveille, Yu, & Milberg, 2007) included participants who were 60 and older. Only one study (Appenzeller et al., 2004) specifically investigated RA patients. Dunlop et al. (2005) assessed participants with various kinds of arthritis, including RA. The remaining 25 studies investigated community-dwelling, non-institutionalized, older adults without dementia but with or without a wide range of chronic health conditions.

Summary of Literature Review of the Relationship between Cognitive Function and Physical Function in Older Adults with RASummary of Literature Review of the Relationship between Cognitive Function and Physical Function in Older Adults with RASummary of Literature Review of the Relationship between Cognitive Function and Physical Function in Older Adults with RASummary of Literature Review of the Relationship between Cognitive Function and Physical Function in Older Adults with RASummary of Literature Review of the Relationship between Cognitive Function and Physical Function in Older Adults with RASummary of Literature Review of the Relationship between Cognitive Function and Physical Function in Older Adults with RASummary of Literature Review of the Relationship between Cognitive Function and Physical Function in Older Adults with RA

Table 1: Summary of Literature Review of the Relationship between Cognitive Function and Physical Function in Older Adults with RA

Four studies (Eggermont, Milberg, Lipsitz, Scherder, & Leveille, 2009; Fitzpatrick et al., 2007; Rosano et al., 2005; Samper-Ternent, Al Snih, Raji, Markides, & Ottenbacher, 2008) examined the relationship between cognitive function and physical function, with physical function as the independent variable and cognitive function as the dependent variable. The remaining 23 studies assessed the association with cognitive function as a predictor variable and physical function as an outcome variable. The use of a wide variety of neuropsychological tests to assess cognitive function yielded confusion and complications when attempting to synthesize and compare studies. Researchers used three methodologies to assess physical function: (a) self-reported or observer-reported functional difficulties in ADLs or IADLs only (11 studies), (b) performance-based tests only (7 studies), or (c) both (9 studies). All but two (Appenzeller et al., 2004; Kempen & Ormel, 1998) found a significant relationship between cognitive function and physical function, as well as other factors that might affect the association.

Studies that used subjective measures—self-reports or observer-reports of difficulties in performing daily activities—appeared to use the concept of disability (i.e., difficulty performing activities in any domain of daily life due to health problems) in the Disablement Process Model (DPM, Verbrugge & Jette, 1994) as an outcome measure of physical function. Studies that used objective measures—performance-based tests—appeared to use the concept of functional limitations (i.e., restrictions in performing fundamental physical actions) in the DPM as an outcome measure of physical function. Similarly, studies that included both subjective and objective measures appeared to use a combined concept of functional limitations and disability. Most studies in this review used the combined concept of functional limitations and disability as an outcome assessment of physical function, no matter what types of measures were used.

Using Subjective Measures for Physical Function Assessment

Eleven studies (Appenzeller et al., 2004; Dunlop et al., 2005; Eggermont et al., 2009; Grigsby et al., 1998; Hébert et al., 1999; Kelly-Hayes, Jette, Wolf, D’Agostino, & Odell, 1992; Leveille et al., 1998; Moritz, Kasl, & Berkman, 1995; Raji, Al Snih, Ray, Patel, & Markides, 2004; Royall, Palmer, Chiodo, & Polk, 2004; Spiers et al., 2005) assessed self-reported or observer-reported functional difficulties in ADLs or IADLs to measure physical function. Despite some disagreement regarding the use of self-reported data, several studies found that self-reported daily activities had high test-retest reliability, even among older adults with cognitive impairment (Raji et al., 2004; Smith et al., 1990). Some studies also found that proxy assessments of patients’ abilities to perform daily activities had significant accordance with patients’ assessments (Raji et al., 2004; Weinberger et al., 1992). Therefore, subjective measures, (i.e., self-report and observer-report) may provide reliable information regarding physical function difficulties in older adults.

Only one study (Appenzeller et al., 2004) examined the prevalence of cognitive impairment and risk factors for its occurrence in RA patients using a comprehensive neuropsychological test battery that extends beyond general mental status screening examinations, such as the Mini-Mental State Examination (MMSE, Folstein, Folstein, & McHugh, 1975). Cognitive impairment was observed in 30% of RA patients and 7.5% of healthy control participants. RA patients had significantly worse outcomes in verbal fluency, logic memory, and short-term memory. In further analyses, cognitive impairment was not significantly correlated with disability or with other variables, including duration of RA, current use of corticosteroid therapy, cumulative dose of corticosteroid agents, and neurological abnormalities (Appenzeller et al., 2004). Systemic inflammatory process, chronic pain, psychological distress, and continuous corticosteroid use were suggested as the possible mechanisms that might be linked to the incidence of cognitive impairment in these patients.

This study has several limitations. The sample was small, and all participants were White. Most participants were women, relatively young, and had low educational levels. Disability was assessed by only one functional classification, and it was not a primary outcome measure. However, the findings have important implications because the study examined the frequency of cognitive impairment and its possible association with disability in RA patients who had not been widely investigated. In addition, possible explanations for the incidence of cognitive impairment in RA patients were offered despite the lack of statistically significant results.

Dunlop et al. (2005) examined the prevalence of functional limitations and functional decline over 2 years among older adults with various types of arthritis. Cognitive impairment was assessed using a general mental status screening test and memory tests as a possible predictor of functional decline. Researchers found that 19.7% of participants had baseline functional limitations, including 12.9% with at least one ADL limitation, 5.6% with two or more, and 2.9% with three or more. Functional decline over 2 years was reported in 13.6% of people without severe baseline functional limitations (i.e., three or more ADL limitations). Lack of regular vigorous physical activity was the most prevalent risk factor. Other significant predictors for functional decline included older age, cognitive impairment, depressive symptoms, diabetes, physical limitations, no alcohol use, stroke, and vision impairment (Dunlop et al., 2005).

The physical activity assessment did not provide specific information on the types or levels of activities in which people engaged, and whether or not people were able to perform physical activity (Dunlop et al., 2005). As people with severe functional limitations at baseline were excluded, the predictors for functional decline were analyzed with participants most likely to be capable of physical activities. However, the findings of this study have important implications for public health. This study included a large population-based cohort of older adults with one of the most disabling diseases, arthritis. In addition, the finding that regular vigorous physical activity had a beneficial effect on functional outcomes is amenable to public health prevention and promotion programs.

The remaining nine studies found significant cross-sectional and longitudinal associations between poor cognitive function and physical function difficulties in community-dwelling older adults with diverse health conditions. While six studies assessed cognitive function using only a general mental screening test, primarily the MMSE, three studies (Eggermont et al., 2009; Grigsby et al., 1998; Royall et al., 2004) assessed cognitive function using a set of neuropsychological tests. Eggermont et al. (2009) examined the relationship between physical activity and cognitive function, specifically executive function, as well as possible mediators. The physical activity scores were significantly associated with executive function test scores after adjusting for age, sex, education, medication use, cardiovascular disease and its risk factors, chronic pain, and depressive symptoms (Eggermont et al., 2009).

Grigsby et al. (1998) evaluated the contribution of cognitive function to self-reported and observer-reported performance of ADLs and IADLs. Both general cognitive status and executive function had statistically significant associations with all physical function measures. Executive function was a predictor of self-reported performance of ADLs and observer-reported performance of IADLs. On the other hand, general cognitive status predicted only observer-reported performance (Grigsby et al., 1998).

Royall et al. (2004) examined the impact of cognitive function, especially executive function, on functional status in adults 70 and older residing in a continuing care retirement community over 3 years. The rate of change in Executive Interview (EXIT25) scores was significantly correlated with the rate of change in IADLs, adjusting for baseline EXIT25 scores, IADLs, age, comorbid disease, and level of care. The rate of change in MMSE scores was not significantly associated with the rate of change in IADLs (Royall et al., 2004).

The findings of these studies imply that some subdomains of cognitive function (e.g., executive function) may be correlated with physical function, whereas others may not. A significant contribution of executive function to the prediction of functional disability even beyond that of general cognitive status was found. Therefore, assessing executive function in addition to general cognitive status may aid in the understanding of functional decline.

Using Objective Measures for Physical Function Assessment

Seven studies (Atkinson et al., 2007; Ble et al., 2005; Bootsmavan der Wiel et al., 2002; Coppin et al., 2006; Raji, Ostir, Markides, & Goodwin, 2002; Rosano et al., 2005; Tabbarah, Crimmins, & Seeman, 2002) used a combination of various performance-based tests to assess physical function. The most frequently used test was a modified version of the Short Physical Performance Battery (Guralnik et al., 1994) consisting of gait speed, chair rising, and standing balance tests for lower extremity function measure. Objective performance-based tests of physical function can increase validity and reproducibility, and have less bias from variations in ethnicity, culture, language, psychological mood, cognition, personality, and educational level than self-reports (Raji et al., 2002).

Two studies (Ble et al., 2005; Bootsma-van der Wiel et al., 2002) assessed upper extremity function using a handgrip dynamometer in addition to lower extremity function. However, handgrip strength was not a primary outcome variable of interest but one of covariates, and the association of cognitive function with handgrip strength was not tested. Nevertheless, these studies are notable because examining both lower and upper extremity function may provide a full range of information regarding physical function.

Ble et al. (2005) examined the association between executive function tests and lower extremity function tasks with different executive/attentional demands in community-dwelling older adults without dementia. After adjustment for age and sex, participants with poor executive function were more likely to be in the lowest tertile for the 4-meter usual pace walking speed, compared with those with good executive function. Participants with poor or intermediate executive function were more likely than participants with good executive function to be in the lowest tertile for 7-meter obstacle fast-pace walking speed, adjusting for all other confounders (Ble et al., 2005). This study has several strengths. The researchers measured two performance-based lower extremity tasks that required different executive/attentional-demanding skills. They also assessed a wide variety of covariates, including sociodemographic variables, chronic health conditions, depressive symptoms, body mass index, and handgrip strength. Executive function was independently associated with lower extremity function that required higher executive/attentional-demanding skills.

Bootsma-van der Wiel et al. (2002) investigated the relative effect of common chronic diseases and general impairments on walking disability in older adults age 85. Walking disability was highly associated with poor mobility in daily life, recurrent falls, and poor well-being. General impairments had higher prevalence rates, higher population attributable risks, and stronger associations with walking disability than common chronic diseases. Among general impairments, cognition and grip strength were most strongly associated with walking disability. The study had the following strengths: (a) a large sample of oldest-old people who had not been widely studied, and (b) it assessed general impairments by various methods according to the International Classification of Impairments, Disabilities and Handicaps standards (Bootsma-van der Wiel et al., 2002). The findings of this study are particularly important from a public health point of view because general impairments in older adults are preventable and curable.

While two studies (Bootsmavan der Wiel et al., 2002; Raji et al., 2002) used only the MMSE, the remaining five studies (Atkinson et al., 2007; Ble et al., 2005; Coppin et al., 2006; Rosano et al., 2005; Tabbarah et al., 2002) used a neuropsychological test battery to assess cognitive function. Although the latter studies did not compare the specific subdomains of cognitive function and general cognitive status, using various neuropsychological tests could add more reliable and comprehensive information than using only the MMSE. All of these studies found significant cross-sectional and longitudinal relationships between cognitive impairment and physical function difficulties.

Using Both Subjective and Objective Measures for Physical Function Assessment

Nine studies (Auyeung et al., 2008; Fitzpatrick et al., 2007; Gill, Williams, Richardson, & Tinetti, 1996; Greiner, Snowdon, & Schmitt, 1996; Kempen & Ormel, 1998; Kuo et al., 2007; Raji et al., 2005; Samper-Ternent et al., 2008; Wang, Van Belle, Kukull, & Larson, 2002) used both subjective and objective measures to assess physical function. By using both subjective and objective measures, these studies can provide more reliable and less biased information regarding physical function.

Auyeung et al. (2008) examined the relationship between cognitive function and performance-based physical function independent of muscle mass, assessed by dual-energy x-ray absorptiometry. Participants with cognitive impairment had weaker grip strengths and performed worse on the two physical function tests (i.e., 6-meter walk speed and chair stand tests). After adjusting for age, appendicular skeletal muscle mass, self-reported physical function score, and comorbid health conditions that could adversely affect the performance-based tests, both male and female participants with cognitive impairment performed consistently worse in all physical function tests (Auyeung et al., 2008). The strength of this study is that the researchers, using both subjective and objective measures, found a significant association between cognitive impairment and both poor muscle strength and physical function independent of muscle mass.

Kempen and Ormel (1998) examined the independent contribution of physical performance and cognitive status to subsequent levels of ADL disability in low-functioning older adults 57 and older. Subsequent ADL disability at 3 years was highly predicted by both physical performance and ADL disability at baseline. ADL disability at baseline was a stronger predictor of subsequent ADL disability than impairments in baseline physical performance. Although cognitive status was slightly related to subsequent ADL disability, there were no independent contributions of cognitive status to subsequent ADL disability. In addition, there was no significant interaction effect of physical performance and cognitive status on subsequent ADL disability (Kempen & Ormel, 1998).

Unlike most other community-based studies that examined relatively healthy older adults, this study included older adults who reported considerable physical limitations at baseline. Non-participants were older, had more chronic health conditions at baseline, and were more impaired than the participants in baseline cognitive status, physical performance, and ADL disability. Therefore, the findings of this study cannot be directly compared to those of the other studies or be generalized.

The remaining seven studies found significant cross-sectional and longitudinal relationships between cognitive impairment and physical function difficulties. Three studies (Gill et al., 1996; Raji et al., 2005; Samper-Ternent et al., 2008) used only the MMSE, but four studies (Fitzpatrick et al., 2007; Greiner et al., 1996; Kuo et al., 2007; Wang et al., 2002) used various neuropsychological tests to obtain comprehensive information. Kuo et al. (2007) specifically examined executive function and investigated the association between executive function, habitual gait speed, and late-life disability in the context of the DPM (Verbrugge & Jette, 1994). Kuo et al. found a potential mediating effect of habitual gait speed in the relationship between impaired cognitive function and disability.

Discussion

Strengths

In this review of research studies that investigated the relationship between cognitive function and physical function in older adults with and without various comorbid health conditions, several strengths deserve mention. First, many studies examined large samples of community-dwelling, older adults without dementia but with various chronic health conditions, which may strengthen the generalizability of the results. Second, two studies (Bootsma-van der Wiel et al., 2002; Hébert et al., 1999) examined the very older population (those age 85 and those 75 and older, respectively), which is most likely to have cognitive impairment, disability, and functional dependence. The findings of these studies have significant clinical implications for assessments and interventions for this cohort—the fastest-growing segment of the older population, which has not been widely studied.

Third, diverse ethnic/racial groups, including Hispanic, Mexican American, African American, and Chinese, were studied in many different countries. Fourth, 15 studies used prospective longitudinal study designs conducted over a period of 2 to 10 years. Researchers could find the cross-sectional relationship between cognitive impairment and disability, as well as the longitudinal relationship between changes in cognitive function and subsequent functional decline. Fifth, the greater utility of performance-based tests in assessing physical function was found even in older adults by comparing the results of subjective and objective measures.

Sixth, most studies examined a wide range of confounding factors, including sociodemographic variables, depressive symptoms, comorbid health conditions, lifestyle behavioral factors, and pain, that could affect the relationship between cognitive function and physical function. One study by Atkinson et al. (2007) found a mediating effect of depressive symptoms in the relationship between cognitive function and physical function. In addition, Raji et al. (2002) found that good emotional health status moderated the effect of impaired cognitive function on subsequent functional difficulties. These findings imply that good emotional health may play an important role for older adults in improving functional status and maintaining independence in daily activities. Gait speed (Kuo et al., 2007) and handgrip muscle strength (Raji et al., 2005), measured by performance-based tests, were found to be potential mediating factors in the association between impaired cognitive function and disability. The findings of these studies emphasize the effectiveness of active participation in physical exercise. Older adults may benefit from any kind of physical activity in order to delay functional decline and improve physical independence.

Limitations

Despite these strengths, several limitations should be noted. First, the use of diverse terms and concepts regarding cognitive function and physical function hindered researching and comparing studies. Most researchers did not specifically define the main concepts of cognitive function and physical function used in their studies. A number of terms, including cognition, cognitive function, cognitive status, neuropsychological status, general mental status, and executive cognitive function were used to represent the concept of cognitive function. The heterogeneity of criteria for classifying cognitive impairment also precluded study comparisons. Many studies followed the definitions of functional limitations and disability in the DPM (Verbrugge & Jette, 1994). However, most of the studies used both concepts interchangeably to represent the notion of physical function and assessed them as functional outcomes. Kelly-Hayes et al. (1992) distinguished between the two concepts and found that disability had more social impact on an individual’s daily life than functional limitations. The findings of the study by Gill et al. (1996) supported the DPM pathway from impairments to disability by demonstrating the independent contributions of functional impairments to further disability and functional independence.

Second, because no standardized test battery exists for examining cognitive function, a wide range of measures was used. Fourteen studies used only one instrument, primarily the MMSE, to assess global cognitive function. Thirteen studies used various neuropsychological tests in addition to the measurement of global mental status. Some studies (Atkinson et al., 2007; Eggermont et al., 2009; Grigsby et al., 1998; Rosano et al., 2005; Royall et al., 2004) examined executive function in addition to global cognitive function and found a dissociated impact of general mental status and executive function on physical function. In general, both impaired global cognitive function and executive function were associated with poor functional outcomes, with a stronger impact of executive function on physical function in older adults. Some studies (Ble et al., 2005; Coppin et al., 2006; Kuo et al., 2007) that specifically assessed executive function found a significant association between impaired executive function and poor physical function. Even among studies that examined the same specific subdomain (i.e., executive function) of cognitive function, researchers used different types of neuropsychological tests, which might lead to unnecessary confusion and complications in comparing study results.

Assessing executive function is important in people with chronic diseases, including RA. Executive function encompasses a set of brain processes that regulate and integrate other cognitive activities (Bryan & Luszcz, 2000). Specifically, executive function controls a group of cognitive actions such as goal planning, cognitive flexibility, selective attention, concept formation, abstract thinking, rule acquirement and adherence, and initiating appropriate behaviors and inhibiting inappropriate ones (Keil & Kaszniak, 2002). Many interventions for RA often require intact executive function to make changes in knowledge, behaviors, and lifestyles. Therefore, poor executive function may aggravate poor physical, psychological, and social health in people with RA (Abeare et al., 2010). Using only the MMSE or other global cognitive function screening tests may be insufficient and inappropriate in assessing this complex cognitive subdomain. Therefore, examining cognitive function using a set of standardized neuropsychological tests is necessary.

Third, many studies used either self-reported information or performance-based tests in assessing physical function; few studies used both. Both self-reported and proxy-reported information on daily activities have been found to be reliable. However, Elam et al. (1991) found that patients, as compared with proxies, were more likely to report functional difficulties in certain ADLs. One study (Fitzpatrick et al., 2007) found that cognitive function was significantly correlated with performance-based tests but not with self-reported measures of disability. Using both subjective and objective measures of physical function may provide more reliable and comprehensive information in older adults who have a high risk for cognitive and physical impairment.

Fourth, most studies that used objective physical function measures only assessed lower extremity function. Only two studies (Ble et al., 2005; Bootsma-van der Wiel et al., 2002) assessed upper extremity function in addition to lower extremity function. However, grip strength was not a variable of interest but one of the covariates, and the association of cognitive function with grip strength was not tested. As many RA patients have fine hand-motor dysfunction, assessing upper extremity function in addition to lower extremity function may be important to obtain a full range of information regarding physical function.

Finally, no study examined the relationship between cognitive function and physical function in older adults with RA. Most studies conducted secondary analyses using a large population-based sample of older adults with various chronic health conditions, including arthritis. One study by Appenzeller et al. (2004) specifically compared RA patients with healthy control participants. However, the primary purpose of this study was not to examine the relationship between cognitive function and physical function. Rather, the researchers found the lack of association indirectly while in the process of investigating risk factors for incident cognitive impairment in RA patients. Because Dunlop et al. (2005) examined older adults with various types of arthritis, the relationship of cognitive impairment with physical function specific to people with RA is difficult to discern from this study.

Suggestions for Future Studies

Based on the findings, strengths, and limitations of the reviewed studies, some suggestions can be made for future studies. Most of all, it is important to use consistent and precise terms and concepts to avoid unnecessary confusion in comparing study findings. Development of standardized tests for the assessment of cognitive function is essential. Comparing certain subdivisions of cognitive function with global mental status would provide additional information.

Both self-reported and performance-based assessments of physical function may be needed to obtain more reliable and comprehensive information. A large, multiethnic/racial sample of older adults with RA should be studied. A longitudinal study design would provide more valuable information, including causality and time-dependent factors.

Implications for Clinical Practice

As mentioned previously, intact cognitive function in patients with chronic diseases is important for performing fundamental daily activities and managing complex health conditions such as RA. Identifying factors that exacerbate or enhance physical function is an essential step in health management and may support the continued development of effective interventions for RA patients. The findings of this literature review emphasize the risk of cognitive impairment in RA patients and the importance of assessing cognitive status in clinical settings to identify risk factors of functional decline. Some individuals with RA may benefit from interventions modified for patients with cognitive impairment or designed to improve cognitive function; such interventions may, in turn, be effective in enhancing or maintaining physical function and ultimately in promoting well-being.

Conclusion

As increasing numbers of older adults may live with RA and RA-attributable functional limitations and disability, identifying factors that exacerbate or enhance physical function is an important initial step for its effective management. Older adults with RA may benefit from preventive intervention programs designed to decrease aggravating factors, such as cognitive impairment or depression, and to increase promoting factors, such as exercise or good emotional health. More studies should investigate the relationship between cognitive function and physical function in older adults with RA to eventually improve functional status, independence, and quality of life.

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Summary of Literature Review of the Relationship between Cognitive Function and Physical Function in Older Adults with RA

Reference Sample Design Variables Measures
Cognitive Function Physical Function
Using Subjective Measures for Physical Function Assessment (N = 11)
Appenzeller, Bertolo, & Costallat (2004) N = 80 Patients with RA (n = 40) were compared to age and sex matched healthy controls (n = 40) in Brazil Cross-sectional study IV

Cognitive impairment

DV

Disability

MMSE

Logic memory tests

Short and long memory tests

Verbal fluency tests

Attention tests

Functional classification of Steinbrocker

Dunlop, et al. (2005) N = 5715 Older adults aged 65 years and older with arthritis from the Health and Retirement Study Prospective longitudinal study IV

Cognitive function

DV

Functional limitations

Functional decline

A modified version of the Telephone Interview for Cognitive Status

Immediate and delayed verbal recall tests

Serial 7’s test

Functional limitations in IADLsor ADLs

Functional decline: 2-year progression to a more severe level of functional limitations

Eggermont, Milberg, Lipsitz, Scherder, & Leveille (2009) N = 544 Community-dwelling older adults aged 70 years and older residing in Boston area from the Maintenance of Balance, Independent Living, Intellect, and Zest in the Elderly Boston Study Cross-sectional study IV

Physical activity

DV

Cognitive function

Letter fluency and category fluency tests

TMT Part A and B

Clock-in-a-Box Test

Hopkins Verbal Learning Test-Revised

Physical Activity Scale for the Elderly

Grigsby, Kaye, Baxter, Shetterly, & Hamman (1998) N = 1158 Community-dwelling persons aged 60–99 years who were Hispanics (n = 637) or non-Hispanic whites (n = 521) from the San Luis Valley Health and Aging Study Cross-sectional study IV

General mental status

Executive function

DV

Physical function

MMSE

Behavioral Dyscontrol Scale

An abbreviated version of the Structured Assessment of Independent Living Skills

Self-reported performance of daily tasks in seven ADLs and eight IDLs

Hébert, Brayne, & Spiegelhalter (1999) N = 504 Community-dwelling older adults aged 75 years and older living in Sherbrooke, Quebec, Canada Prospective longitudinal study IV

Cognitive status

DV

Functional decline

Functional improvement

A modified MMSE

Functional Autonomy Measurement System

Kelly-Hayes, Jette, Wolf, D’Agostin o, & Odell (1992) N = 1453 Community-dwelling older adults living in Framingham, MA from the Framingham Study Cross-sectional study IV

Cognitive function

DV

Disability

Functional limitations

MMSE

Self-reported disability questionnaire in six ADLs from the Katz and Mahoney and Barthel indexes

Observed functional limitations

Leveille et al. (1998) N = 3585 Community-dwelling women (whites = 2694, blacks = 891) aged 65 years and older with MMSE≥18 living in East Baltimore, MD from the Women’s Health and Aging Study Cross-sectional study IV

Cognitive function

DV

Functional difficulties

MMSE

Functional difficulties in ADLs, IADLs, and mobility (walking two or three blocks and climbing 10 steps without resting)

Moritz, Kasl, & Berkman (1995) N = 1865 Community-dwelling older adults aged 65 years and older living in New Haven, CT who were initially free of ADL limitations from the Yale Health and Aging Project Prospective longitudinal study IV

Cognitive function

DV

Persistent incident ADL limitations

Pfeiffer’s Short Portable Mental Status Questionnaire

A modified version of the Katz ADL Scale

Rosow-Breslau Scale

Raji, Al Snih, Ray, Pate & Markides (2004) N = 2731 (non-ADL disabled at baseline = 2431) A population-based sample of Mexican-Americans aged 65 years and over from the Hispanic Established Populations for the Epidemiologic Study of the Elderly Prospective longitudinal study IV

Cognitive function

DV

Functional disability

MMSE

A modified version of the Katz ADL scale

Royall, Palmer, Chiodo, & Polk (2004) N = 547 Older adults aged 70 years and older residing in a continuing-care retirement community, the Air Force Villages, from the Freedom House Study Prospective longitudinal study IV

Executive control function

DV

Functional status

MMSE

Executive Interview

Older Adults Resources Scale: self-reported information on ADLs, IADLs, health history, health care use, and current medications

Spiers et al. (2005) N = 7913 Older adults aged 65 years or older in five urban and rural centers in England and Wales from the Medical Research Council Cognitive Function and Ageing Study Prospective longitudinal study IV

Cognitive function

DV

Disability

MMSE

A modified Townsend ADL scale covering nine ADLs/IADLs

Interviewer’s rated mobility

Using Objective Measures for Physical Function Assessment (N = 7)
Atkinson et al. (2007) N = 2349 Nondisabled, well-functioning black and white older adults aged 70–79 years residing in Pittsburgh, PA and Memphis, TN from the Health, Aging and Body Composition Study Prospective longitudinal study IV

Global cognitive function

Executive control function

DV

Gait speed decline

A modified, expanded version of the MMSE

Clock drawing task

15-item Executive Interview

20-meter gait speed test

Ble et al. (2005) N = 926 Community-dwelling older adults aged 65 years and older without dementia, stroke, Parkinsonism, visual impairment, or current treatment with neuroleptics residing in Greve, Chianti and Bagno, Ripoli, in Italy from the InChianti Study Cross-sectional study IV

Executive function

DV

Lower extremity function

MMSE

TMT Part A and B

4-meter usual pace walking and 7-meter obstacle fast pace walking tests

Handgrip dynamometer

Bootsmavan der Wiel et al. (2002) N = 599 Older adults aged 85 years from the Leiden 85-plus Study in the Netherlands Cross-sectional study IV

Cognitive impairments

DV

Walking disability

MMSE

6-meter walking test

Difficulties walking (indoors/outdoors/stairs), part of the Groningen Activity Restriction Scale

Handgrip dynamometer

Coppin et al. (2006) N = 737 Community-dwelling non-demented older adults aged 65 years and older residing in Greve, Chianti and Bagno, Ripoli, in Italy from the InChianti Study Cross-sectional study IV

Executive cognitive function

DV

Physical performance

MMSE

TMT Part A and B

Gait speed tests: Complex vs. reference walking tests

Raji, Ostir, Markides, & Goodwin (2002) N = 2068 Community-dwelling Mexican Americans aged 65 years and older with MMSE scores ≥18 at baseline and complete data on a summary performance measure at 2-year follow-up from the Hispanic Established Population for the Epidemiological Study of the Elderly Prospective longitudinal study IV

Cognitive function

Emotional health

DV

Lower body function

MMSE

CES-D

The summary performance measure of lower body function: A timed 8-foot walk, rising from a chair five times, and a hierarchical standing balance task

Rosano et al. (2005) N = 2893 Well-functioning, nondisabled black and white older adults aged 70–79 years residing in Pittsburgh, PA and Memphis, TN from the Health, Aging and Body Composition Study Cross-sectional study IV

Physical function

DV

Cognitive function

Teng-modified MMSE

Digit symbol substitution test

Gait speed tests: 6-meter usual walk and narrow walk

Repeated chair stand tests

Standing balance test

Tabbarah, Crimmins, & Seeman (2002) N = 488 High-functioning, disability-free older adults aged 70–79 years from the MacArthur Research Network on Successful Aging Community Study Prospective longitudinal study IV

Cognitive performance

DV

Physical performance

The sum of the performances on five subscales (spatial memory, similarity of abstract concepts, language, delayed verbal memory, and spatial orientation)

Delayed Span Test

Boston Naming Test

Wechsler Adult Intelligence Scale-Revised

Drawing test

Five routine physical tasks

Six novel/attentional demanding physical tasks

Using both Subjective and Objective Measures for Physical Function Assessment (N = 9)
Auyeung et al. (2008) N = 4000 Community-dwelling Chinese elderly aged 65 years and older Cross-sectional study IV

Cognitive function

Muscle strength

Muscle mass

DV

Physical function

The cognitive part of the Chinese version of the Community Screening Instrument of Dementia

Dual-energy X-ray absorptiometry (whole body muscle mass and appendicular skeletal muscle mass)

Grip strength

Chair stand tests

6-meter gait speed

Physical Activity Scale for the Elderly

Fitzpatrick et al. (2007) N = 3035 High-functioning, non-demented older adults aged 75 years and older from the Ginkgo Evaluation of Memory Study Cross-sectional study IV

Physical function

DV

Cognitive function

Telephone Interview for Cognitive Status questionnaire

A modified MMSE

14 neuropsychological tests

Self-reported ADLs and IADLs

Mobility

Upper extremity strength

Difficulties in walking a half mile

15-foot usual and rapid pace walk tests

Gill, Williams, Richardson, & Tinetti (1996) N = 945 Community-dwelling persons aged 72 years and older from the Project Safety cohort living in New Haven, CT, who were nondisabled at baseline Prospective longitudinal study IV

Cognitive status

Physical performance

DV

Functional dependence in ADLs

MMSE

Seven items from a modified version of the Katz ADL Scale

A composite measure of physical performance: Walking back and forth over a 10-foot course, turning in a full circle, and standing up/sitting down from a hard-back chair three times with arms folded

Greiner, Snowdon, & Schmitt (1996) N = 678 Elderly nuns who completed cognitive and physical function tests from the Nun Study of Alzheimer’s disease and aging Prospective longitudinal study IV

Cognitive function

DV

Physical function

Neuropsychological tests

MMSE

Self-reported ADLs

Performance-based ADLs from the Performance Test of Activities of Daily Living, the Simulated Activities of Daily Living Examination, and a modified version of the Blessed Dementia Scale

Kempen & Ormel (1998) N = 753 Community-dwelling older adults aged 57 years and older who reported substantial physical limitations from the Groningen Longitudinal Ageing Study in the Netherlands Prospective longitudinal study IV

Cognitive status

Physical performance

DV

ADL disability

MMSE

Physical performance tests: Putting on/off a jacket, walking six meters including a 180 degree turn after three meters, and five chair standing tests

Physical functioning scale of the Short Form-20 General Health Survey

11-item ADL subscale of the Groningen Activity Restriction Scale

Kuo, Leveille, Yu, & Milberg (2007) N = 2481 Older adults aged 60 years and older from the National Health and Nutrition Examination Survey Cross-sectional study IV

Cognitive function including executive function

Habitual gait speed

DV

Disability in ADL, IADL, leisure/social activities, and lower extremity mobility

2-minute timed Digit Symbol Substitution Test, a component of the Wechsler Adult Intelligence Test and a test of visuo-spatial and motor speed-of-processing

12-item Physical Functioning Questionnaire: Difficulty in ADL, IADL, leisure/social activities, and lower extremity mobility

20-foot timed walk test

Raji, et al. (2005) N = 2281 Community-dwelling Mexican-Americans aged 65 years and older with no ADL disability at baseline from the Hispanic Established Population for the Epidemiological Study of the Elderly Prospective longitudinal study IV

Cognitive function

DV

Change in handgrip muscle strength

Incidence of functional disability

MMSE

A hand-held dynamometer

A modified version of the Katz ADL Scale

Samper-Ternent, Al Snih, Raji, Markides, & Ottenbacher (2008) N = 1370 Community-dwelling Mexican-Americans aged 65 years and older with MMSE scores ≥21 at baseline from the Hispanic Established Population for the Epidemiological Study of the Elderly Prospective longitudinal study IV

Frailty

DV

Cognitive function

MMSE

Frailty Index: Unintentional weight loss of >10 pounds, lowest 20% in grip strength using a hand-held dynamometer, two self-reported exhaustion items from the CES-D, lowest 20% in 16-feet walk-time, and lowest 20% in Physical Activity Scale for the Elderly score

Wang, Van Belle, Kukull, & Larson (2002) N = 2581 Cognitively intact older adults aged 65 years and older from the Group Health Cooperative members in Seattle in the Adult Changed in Thought Study (mean follow-up time = 3.4 years; range = 0–7 years) Prospective longitudinal study IV

Cognitive function

DV

Functional status

Functional decline

Cognitive Abilities Screening Instrument

Memory and general function evaluation

Three Reaction Time-simple and choice reaction time test

Self-reported ADLs and IADLs

Performance-based Physical Function Testing:10-foot timed walk, five repeated chair stand time, standing balance, and grip strength (dominant hand)

Keypoints

Shin, S.Y. (2012). The Relationship Between Cognitive and Physical Function in Older Adults with Rheumatoid Arthritis: A Literature Review. Journal of Gerontological Nursing, 38(9), 33–42.

  1. For people with chronic diseases such as rheumatoid arthritis (RA), intact cognitive function is crucial for performing daily activities and adhering to health management skills.

  2. Older adults with RA may have the increased burden of physical function difficulties due to the impact of both age-related and RA-related cognitive impairment.

  3. As increasing numbers of older adults may live with RA and functional limitations and disability attributable to RA, identifying factors that exacerbate or enhance physical function is an important initial step for its effective management.

  4. More studies are needed that investigate the relationship between cognitive function and physical function in older adults with RA to eventually improve functional status, independence, and quality of life.

Authors

Dr. Shin is Assistant Professor, College of Nursing, Keimyung University, Daegu, South Korea.

The author has disclosed no potential conflicts of interest, financial or otherwise. Dr. Shin acknowledges Dr. Patricia Katz, Dr. Laura Julian, and Dr. Margaret Wallhagen for their encouragement, guidance, and support.

Address correspondence to So Young Shin, PhD, RN, GCNS-BC, Assistant Professor, College of Nursing, Keimyung University, 1095 Dalgubeoldaero, Dalseo-Gu, Daegu, South Korea 704-701; e-mail: fantasy45@gmail.com.

Received: October 07, 2011
Accepted: March 14, 2012
Posted Online: August 17, 2012

10.3928/00989134-20120807-03

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