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Correspondence: Address correspondence to Melissa Nelson, Institute for Health, Health Care Policy and Aging Research, Rutgers, The State University of New Jersey, 30 College Avenue, New Brunswick, NJ 80901. E-mail: mnelson{at}ifh.rutgers.edu.
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Abstract |
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Key Words: Burden • Competence • Functional decline • Proxies • Social exchange
Burden can be measured both subjectively, evaluating the strain or dissatisfaction experienced by a caregiver while providing care, or objectively, with a count of how many hours per week a caregiver spends providing care. Prior research on the effect of patients' strokes on caregiver burden and health has found mixed results, although these studies usually have focused on static assessments of patient functioning without reference to changes over time. Some studies have found worse patient physical functioning to be associated with higher levels of subjective caregiver burden (Blake & Lincoln, 2000; Choi-Kwon, Kim, Kwon, & Kim, 2005; Heuvel, de Witte, Schure, Sanderman, & Meyboom-de Jong, 2001). Oftentimes, however, patient health status does not predict subjective caregiver burden (Anderson et al., 1995; McCullagh, Brigstocke, Donaldson, & Kalra, 2005), or the relationship is inconsistent across different time points (Bugge, Alexander, & Hagen, 1999). The relationship between patient physical health and caregiver health is even less well established (Clark et al., 2004; McCullagh et al.). Furthermore, despite the fact that many stroke patients have significant neurological deficits in addition to physical functioning deficits, the relationships between patient neurological functioning and caregiver outcomes have not been explored extensively (Anderson et al.; Bugge et al.).
We propose that understanding the role of patient physical and neurological functioning in caregiver outcomes requires an examination of change in patient functioning over time in addition to baseline functioning. However, measures of change in patient health are rare in the literature, and studies with these measures show inconsistent results (Beach, Schulz, Yee, & Jackson, 2000; Tooth, McKenna, Barnett, Prescott, & Murphy, 2005). One study found that changes in patients' functional independence and physical health were associated with time spent caregiving, social burdens, and caregiver strain, but they were not associated with emotional, physical, or developmental burdens. Furthermore, these relationships were inconsistent over time (Tooth et al.). Little is known about the relationship between change over time in patient neurological functioning and caregiver outcomes.
Theoretical Model
To examine the effects of change in patient functioning on caregiver outcomes, we used principles from social exchange theory. Social exchange theory focuses on relationships between members of a dyad or a larger network. According to this theory, members of a dyad are dependent on one another and act in ways that increase positive outcomes for themselves. Additionally, these positive outcomes have diminished marginal utility over time; that is, if one member of a relationship receives the same positive outcome many times and in close succession, the relative value of this outcome to the individual decreases (Molm & Cook, 1995). Exchanges between members of a dyad can be either emotional or material in nature (Mutran & Reitzes, 1984).
Although much of social exchange theory focuses on the structural aspects of relationships (such as who has more power), the subjective components of a relationship, such as satisfaction and loneliness, are also important (Rook, 1987). Most studies that have examined caregiving burden relating to dissatisfaction or patient demands within a social exchange framework focus on measures of patient functioning at one point in time rather than measures of changing functioning (Call, Finch, Huck, & Kane, 1999; Raschick & Ingersoll-Dayton, 2004; Wright & Aquilino, 1998). Because the needs of patients and thus the caregiving situation change with time, measures of change in patient functioning, rather than cross-sectional measures, may be more appropriate to use in studies of caregiver outcomes. When evaluating a relationship, members of a dyad look for changes in the status of the relationship (Molm, 1991). Because a stroke is a sudden event, it provides a reference point from which change in a relationship might be evaluated. This may be especially relevant for a family member who goes from being in a reciprocal relationship to one that is more asymmetrical, in which she or he begins providing care to the other member of the relationship.
Our objective in this study is to examine the relationship between declining health of stroke patients and subsequent caregiver burden and health (see Figure 1). Here, we study the primary caregivers identified by patients. We expect that the magnitude of decline in a patient's neurological or physical status will be associated with both increased subjective and objective caregiver burden as well as subsequent declines in caregiver health.
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Worsening patient functioning also might increase asymmetry in physical demands of providing care, leading to increased objective burden (time spent providing care). Objective burden could be impacted by both static and changing levels of functioning, because a patient will still require some set amount of care whether or not her or his functional ability is declining.
In addition, interaction with a loved one suffering from declining physical or neurological functioning might lead to a greater emotional impact. The changing physical and emotional demands in a relationship might affect caregiver health. We think that, similar to the relationship between patient functioning and subjective burden, the relationship between change in functioning and caregiver health will be stronger than the relationship between static patient functioning and health. Caregivers of patients with larger declines in functioning may have a harder time adjusting to the patients' increasing needs. Because prior research has shown more significant results with caregiver burden than with caregiver health, we expect that this relationship will be weaker than the relationships for subjective and objective burden (Blake & Lincoln, 2000; Heuvel et al., 2001).
We test the following three hypotheses: First, larger changes in patient physical and neurological functioning after stroke will predict higher levels of subjective caregiver burden. Second, larger baseline deficits and larger changes in patient physical and neurological functioning after stroke will predict higher levels of objective caregiver burden. Third, larger changes in patient physical and neurological functioning after stroke will predict decreased caregiver health.
Stroke patients often cannot respond on their own behalf, particularly if the stroke was severe. In this case, enlisting a family member to provide a proxy response allows the challenges faced by these more severely ill or communication-impaired patients to be studied. However, studying caregiving in situations in which the caregiver also acts as the proxy respondent raises issues, because the caregiver's assessment of the patient may be related to his or her sense of burden or health status in ways that differ from those of caregivers who do not act as proxy respondents. We examine the effects of proxy status within the context of each hypothesis.
To address our hypotheses, we used data from a longitudinal study of stroke patients, that is, the Quality of Life After Stroke Study, which is a component of the Minnesota Stroke Survey (MSS). This study was approved by the Institutional Review Boards of the University of Wisconsin and the University of Minnesota, and we obtained informed consent from all participants.
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Methods |
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Patients, proxy respondents for patients, and primary caregivers were included in this analysis. Proxy respondents were used for patients who had difficulties communicating or who had severe impairment. In all but one case, the proxy was the patient's caregiver (so the caregiver answered questions for the patient and for himself or herself). Seventy-six percent of patients or proxies in the original study identified a primary caregiver, and only patients or proxies with caregivers were included in this analysis (N = 356). Consequently, the sample for our analysis included 281 patients and 75 proxies who identified an informal caregiver and were interviewed within 4 months of discharge, along with their 356 caregivers. Although the focus of this analysis is caregiver outcomes, we used patient interview data in order to gain an understanding of how patient functioning could affect caregiver health and burden.
Data Collection
Patient or Proxy Interviews
Trained interviewers conducted in-person and telephone surveys of patients or their proxies within 4 months of and at approximately 12 months after hospital discharge. We include only the interviews conducted within 4 months (number of days, Mdn = 55) of hospital discharge in this study.
Caregiver Interviews
Trained interviewers also conducted in-person and telephone surveys of caregivers identified by patients or serving as proxies for patients. All caregivers completed interviews.
Hospital Chart Abstraction
Trained registered nurses abstracted information from charts for index hospitalizations for all patients in this analysis. To ensure interrater reliability, each month a random sample of 5% of charts completed by one auditor in the previous month was reabstracted by another auditor. Difference reports between original audits and reaudits were reviewed on a monthly basis. We conducted interrater reliability assessments for key data elements in the abstraction, identifying moderate to high kappa values (
= 0.6–0.8) for most data elements.
Clinic Chart Abstraction
Trained registered nurses also abstracted information from stroke patients' outpatient clinic charts for all visits (Mdn = 2) occurring within 1 year of the stroke discharge. (We used only those visits occurring within 4 months of discharge for this analysis.) To ensure interrater reliability, a random sample of 7% of cases was reaudited during the outpatient audit process. We found fair to moderate kappa values ( = 0.4–0.6) for functional and neurological status. We found moderate to high kappa values ( = 0.6–0.8) for assessments of the presence or absence of specific symptoms.
Variables
The dependent variables were caregiver subjective and objective burden as well as caregiver health. The explanatory variables of interest were baseline measures of patient functioning as well as worsening in patient physical and neurological functioning. Baseline refers to functioning before hospitalization. We controlled for other patient, caregiver, and sociostructural characteristics.
Caregiver Burden
Subjective caregiver burden was ascertained by the Sense of Competence Questionnaire (SCQ) in the caregiver interview (Vernooij-Dassen, Persoon, & Felling, 1996). This questionnaire was originally developed for caregivers of dementia patients but is reliable and valid for caregivers of stroke patients as well (Scholte op Reimer, de Haan, Pijnenborg, Limburg, & Bos, 1998). It includes 27 Likert scale questions and three subscales: subjective burden relating to consequences for caregivers' personal lives, dissatisfaction with the patient, and dissatisfaction with one's own performance as a caregiver. Interviewers asked caregivers to rate their agreement with sentences such as these: "I feel my [patient] makes requests which I perceive to be over and above what he/she needs," "I feel pleased about my interactions with my [patient]", and "I feel that my [patient] seems to expect me to take care of him/her as if I were the only one he/she could depend on" (Scholte op Reimer, de Haan, Pijnenborg, et al.). Intraclass correlation coefficients of the SCQ and its subscales are high in caregivers of stroke patients (dissatisfaction with patient as recipient of care, intraclass correlation coefficients = 0.84; dissatisfaction with self, 0.89; subjective burden relating to consequences for caregivers' personal lives, 0.92; entire scale, 0.93). Scores on the total SCQ have good clinical validity and are significantly associated with patients' functioning, especially with scores on the Mini-Mental State Examination (p =.03) and the Rankin Scale (p <.01; see Scholte op Reimer, de Haan, Pijnenborg, et al.). For this study, we standardized the scores on each subscale to a standard normal distribution; higher scores indicate higher levels of burden.
We measured objective caregiver burden by the number of hours per week that the caregivers reported providing care. We coded the categories so that higher numbers indicate higher levels of burden (3 = 40 hours or more per week, 2 = 20–39 hours per week, 1 = 10–19 hours per week, and 0 = less than 10 hours per week).
Caregiver Health
Caregivers were asked to rate their present health on a scale of 1 to 5 (1 = excellent, 5 = poor). Self-rated health has been found to predict mortality (area under the receiver operated curve, or AUC, = 0.74), hospitalization (AUC = 0.63), and outpatient service use (AUC = 0.61), as well as longer measures of health status such the 36-item Short-Form Health Survey and the Seattle Index of Comorbidity (DeSalvo, Fan, McDonell, & Fihn, 2005).
Patient Physical Functioning
We measured baseline physical functioning in the time period prior to stroke with the reverse-scored Barthel Index (BI; range = 0–100, with higher values indicating worse functioning). The BI measures activities of daily living (ADLs), such as the abilities to dress and bathe oneself (Mahoney & Barthel, 1965). It predicts patient functioning in the future and has high test–retest and interrater reliability ( = 0.87–0.99 and 0.75–0.99, respectively; see Cohen & Marino, 2000; Wolfe, Taub, Woodrow, & Burney, 1991). Patients reported their retrospective assessment of ADL difficulties prior to stroke and their assessment of current ADL difficulties at the time of the interview. We measured worsening in patient physical functioning by subtracting the BI score from the time period prior to stroke from the BI score at the time of the interview.
Covinsky and colleagues (2000) found that retrospective reports of physical functioning are valid measures of patient health status prior to a hospitalization for an acute illness. Patients who were interviewed during a hospital admission and reported being independent in an ADL prior to admission were more likely to be independent in that ADL after recovery from the acute illness than those who were dependent prior to admission (p <.001 for each ADL). This indicates that retrospective measures of physical functioning provide a suitable baseline from which to measure change in functioning caused by stroke. In addition, medical records have been found to be unreliable sources of information about functional status (Bogardus, Towle, Williams, Desai, & Inouye, 2001), further justifying the use of patient recall to obtain this information.
We used the PROC MI procedure in SAS to impute BI scores for a small percentage of individuals (2.5% of BI scores). Because the BI scores at the time of hospital discharge were highly correlated with the BI scores at the time of the interview, we were unable to distinguish change in physical function from prior to stroke to hospital discharge and from hospital discharge to the time of the interview. As a result, we included a single variable in our analyses measuring change in physical function from prior to stroke to the time of the interview.
Patient Neurological Functioning
We measured baseline neurological functioning by means of patient report of the occurrence of a previous stroke. We recognize that history of stroke is not an ideal measure of prior neurological functioning and that other conditions affect neurological status. However, studies suggest that between 37% and 62% of patients have long-term residual neurological deficits after stroke (see Duncan, 1994). Although we recognize the limitations, these studies suggest that the inclusion of prior stroke as a proxy measure for baseline neurological deficit is supported.
We measured worsening in patient neurological functioning as a result of the most recent stroke by using both the Canadian Neurological Scale (CNS) and a variable indicating a notation in the patient's medical record of worsening neurological functioning. The CNS uses data abstracted from hospital records and rates functioning in the following areas: consciousness (awake, drowsy, or coma), orientation, expression and receipt of speech, face weakness, and limb weakness and motor responses (Goldstein & Chilukuri, 1997). The score on the CNS ranges from 0 to 11, with higher values indicating worse functioning. In patients who have initially survived stroke, the CNS has been found to have high interrater reliability (r =.91; Goldstein & Chilukuri) and to be predictive of death within 6 months (Cote et al., 1989; Goldstein & Chilukuri).
We constructed the second measure of worsening in neurological functioning through an abstraction of clinic records. If worsening in neurological functioning was noted in clinic records at any point during the time period from hospital discharge to the last physician visit, we coded this variable as "1," for worsening neurological functioning. If worsening was not noted in the clinic records, then we assigned a value of 0 to this variable.
Other Patient Characteristics
We gathered the gender, age, race, marital status, and education level of patients from patient and proxy interviews.
We used the Charlson Comorbidity Index (range 0–9, with higher values indicating more comorbid conditions) to assess the number of comorbid conditions. It is a weighted sum of diagnoses (we excluded the diagnoses of cerebrovascular disease and hemiplegia). It has been found to have good test–retest reliability (intraclass correlation coefficient = 0.92; see Katz, Chang, Sangha, Fossel, & Bates, 1996). It also has high predictive validity for poor outcomes at discharge and mortality for stroke patients (De Groot, Beckerman, Lankhorst, & Bouter, 2003), with a 1-point increase in the scale corresponding to "a 15% increase in the odds of a poor outcome at discharge (p < 0.005) and a 29% increase in the odds of death by 1 year (p < 0.001)" (Goldstein, Samsa, Matchar, & Horner, 2004, p. 1,943).
Caregiver Characteristics
Information concerning the gender, age, and educational level of caregivers was collected during the caregiver interviews.
Sociostructural Characteristics
Sociostructural characteristics were recorded during interviews of patients, proxies, and caregivers. Patients were asked if they used any paid services at home (homemakers, nurses, or other services) during the time period beginning immediately after leaving the hospital. Caregivers also were asked if they lived with the patient at the time of hospital discharge.
Analysis
We used linear regression to examine the relationship between change in patient functioning and each of the standardized subscales of the SCQ (caregiver subjective burden). We calculated standardized beta coefficients. We used ordinal logistic regression to examine the relationships between change in patient functioning and caregiver health and between change in patient functioning and caregiver objective burden. We also calculated odds ratios (ORs) and 95% confidence intervals (CIs). All models included the following groups of variables: Patient physical functioning, patient neurological functioning, other patient characteristics, caregiver characteristics, sociostructural characteristics, and proxy status. For adjustment purposes, we included the total number of physician visits and the total number of days between discharge and interview as continuous variables. We used Stata version 9 to perform the analyses.
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Reports by caregivers of their sense of competence, objective burden, and self-rated health are presented in Table 2. We standardized the SCQ scores to have M = 0 and SD = 1 in the regression analyses. Of the caregivers, 27% reported high levels of objective caregiver burden (more than 20 hours per week spent caring for the patient). Average caregiver self-rated health was between very good and good at the interview (score, M = 2.4), although 51 caregivers rated their health as being fair or poor.
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Predictors of Objective Burden and Caregiver Health
After adjustment, objective caregiver burden increased with worsened patient neurological, but not physical, functioning (Table 4). Greater stroke severity, as measured by the CNS from hospital records, increased objective burden (OR = 1.14, 95% CI = 1.05–1.30). As was the case with subjective burden relating to consequences for caregivers' personal lives, objective burden was greater for caregivers who were proxies (OR = 2.92, 95% CI = 1.41–6.04). Neither baseline measures nor worsening patient physical and neurological functioning predicted changes in caregiver health.
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Descriptive Differences Between Proxies and Nonproxies
Patients with proxy respondents were older and had more physical comorbidities than those who did not have proxies. We found that the impact of the stroke was much worse for patients with proxies: The mean increase in ADL difficulties from the time period prior to stroke to the interview was only 5.7 points for patients without proxies but 38.3 points for patients with proxies. In addition, on the CNS, the mean score for patients without proxies was 4.9, and it was 7.1 for patients with proxies. Twenty-nine percent of patients without proxies and 48% of patients with proxies had an indication of decline in neurological functioning noted in their clinic records during the time between hospital discharge and the time of the interview.
Caregivers who acted as proxy respondents had more subjective and objective burden than those who did not act as proxies, but caregiver health did not differ between the two groups (Tables 5 and 6). Twenty-one percent of caregivers of patients without proxies and 49% of caregivers of patients with proxies reported high levels of objective caregiver burden (more than 20 hours per week spent caring for the patient).
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Similar to studies by other researchers (Choi-Kwon et al., 2005; Scholte op Reimer, de Haan, Rijnders, Limburg, & Bos, 1998; Tooth et al., 2005), in our study we found subjective burden resulting from consequences on the caregiver's personal life to be more salient than other dimensions of burden in caregivers of stroke patients. However, these other studies focused either on change in patient functional status (Tooth et al.) or on baseline measures of patient disability (Choi-Kwon et al.; Scholte op Reimer, de Haan, Rijnders, et al.) but not both. Our study adds significantly to this nascent literature by including measures of both baseline and change in health and by incorporating neurological functioning in addition to physical functioning. We were able to show that change, rather than baseline functioning, affects subjective caregiver burden the most and that change in neurological functioning might be more relevant than changes in physical functioning.
Worsening in patient functioning, rather than baseline functioning, also predicts caregiver objective burden. In contrast to Tooth and colleagues (2005), we did not find that worsening in patient physical functioning predicted objective burden, but we did find that worsening neurological functioning predicted objective burden. These results were contrary to our expectations that objective burden would be predicted mainly by the patient's baseline health status. We believed that objective burden would be more stable than subjective burden in the face of worsening patient health status, as caregivers might have an established amount of care to provide that corresponded with the consequences of the stroke, regardless of whether or not the caregiver was satisfied with the amount of asymmetry in the relationship. Instead, our results support the conclusion that caregivers who have not had a chance to adjust to increasing neurological deficits in the patient spend more time providing care. Our study is one of very few that have examined hours spent caring as an outcome measure.
Similar to other researchers, we did not find a relationship between worsening patient functioning and caregiver health (Beach et al., 2000; Tooth et al., 2005). We did, however, find that worse caregiver health was predicted for caregivers who were proxies. Other studies of caregiver health that include baseline measures of patient functioning have either not found a relationship between patient baseline health and caregiver health (Clark et al., 2004) or have found the relationship to occur inconsistently over time (McCullagh et al., 2005). To our knowledge, no other studies have simultaneously examined the effect of changes in patient physical and neurological functioning on caregiver health. Other authors have suggested that caregiver health is predicted more by caregiver burden than by changes in patient functional status (Hughes et al., 1999; McCullagh et al.). Future studies will be needed to address the possible link between changes in patient functioning, caregiver burden, and caregiver health.
As with all studies, our study has several limitations. First, we only analyzed data from interviews of caregivers and patients within 4 months of hospital discharge. We might have found significant relationships between patient changes in functioning and caregiver health and burden if we studied a longer time period or had a greater sample size. Second, our sample is not ethnically or racially diverse. It is, however, representative of the Minneapolis–St. Paul metro area. We obtained data from a large HMO that enrolls approximately 10% of the area population. Furthermore, for this analysis, we combined variables representing changes in physical functioning from "prior to stroke to discharge" and from "discharge to the interview" into one measure, as these variables were highly correlated. This did not allow us to distinguish change between these two time periods, but the high correlation suggests that little change occurred. Finally, our R-squared values for overall model fit were low (see Tables 3 and 4), but this is often the case even with extremely good models (Schemper, 2003).
Because we used data from a study that was initially designed to examine other outcomes, we lacked some information that would have been useful for our analyses. Specifically, we did not have explicit measures of reciprocity in the caregiver–patient relationship, and the burden measures reflect objective and subjective changes in the relationship from only the caregiver's point of view. Understanding the patient's emotional experience might improve our understanding of caregiver burden. We also did not have information on unpaid assistance received by caregivers. Unpaid assistance from other family members or friends may lessen the impact of changes in patient status on caregiver burden.
The magnitude of change, not the patient's baseline status, influences a stroke's degree of impact on a caregiver's personal life and the number of hours spent caring for the patient. Our results suggest that a social exchange framework is useful for examining the effects of stroke patient health status on caregiver subjective and objective burden. Caregivers may not be adversely affected by patient characteristics and needs to which they have adapted, but unexpected or large changes in patient neurological functioning cause changes in the symmetry of a relationship and might lead to increased caregiver subjective and objective burden and perhaps even poorer health.
Our results can also be used to identify caregivers at risk for increased burden and poor health outcomes. In particular, caregivers of patients who are more severely ill, have communication difficulties, or have large declines in neurological functioning after stroke might be at risk for decreased health. If these results are confirmed, interventions to protect caregivers may be indicated for severely ill or communication-impaired stroke patients who continue to decline after hospital discharge. Currently, interventions to address the needs of caregivers have been disappointing and criticized as methodologically weak (Knapp, Young, House, & Forster, 2000). More complex interventions to assist carers have been proposed but await randomized controlled trials to evaluate their effectiveness (Robinson et al., 2005). Specifically, assessment and targeting of these interventions to caregivers of certain stroke patients may be indicated. Assuming caregivers accompany patients to physician visits, physicians of stroke patients who have experienced significant declines in functioning also may be engaged and can refer caregivers to specific interventions, support groups, or other community resources.
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We gratefully acknowledge the contributions of Alexandra Wright and Jinn-ing Liou and thank them for their help in data preparation.
1 Division of Health Policy and Management, University of Minnesota, Minneapolis.
2 School of Medicine and Public Health, University of Wisconsin, Madison.
3 HealthPartners Research Foundation, Minneapolis, MN.
4 William S. Middleton Hospital, United States Department of Veterans Affairs, Madison, WI.
5 Department of Medicine—Geriatrics Section, University of Wisconsin, Madison.
6 Division of Epidemiology and Community Health, University of Minnesota, Minneapolis.
Decision Editor: William J. McAuley, PhD
Received for publication June 14, 2007. Accepted for publication January 7, 2008.
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