Journal of Gerontological Nursing

Feature Article 

Effects of Uncertainty on Perceived and Physiological Stress in Caregivers of Stroke Survivors: A 6-Week Longitudinal Study

Eeeseung Byun, PhD, RN; Barbara Riegel, PhD, RN, FAAN, FAHA; Marilyn Sommers, PhD, RN, FAAN; Nancy Tkacs, PhD, RN; Lois Evans, PhD, RN, FAAN

Abstract

Caregivers' stress following a family member's stroke is likely accentuated by its associated uncertainty. The purpose of the current study was to examine the effect of uncertainty on caregivers' perceived and physiological stress (i.e., salivary cortisol). A prospective, longitudinal observational study was conducted with a convenience sample of 40 caregivers and stroke survivors recruited from acute care settings. Linear mixed models were used. Greater uncertainty was associated with higher perceived stress (p < 0.001), but not with physiological stress (p = 0.32 on waking, p = 0.06 evening), over the first 6 weeks post-stroke. A significant association between uncertainty and evening salivary cortisol level was found at 6 weeks post-stroke (p = 0.009). Recognition of uncertainty early in the caregiving period and targeted interventions may be useful in reducing perceived stress for this group. [Journal of Gerontological Nursing, 43(11), 30–40.]

Abstract

Caregivers' stress following a family member's stroke is likely accentuated by its associated uncertainty. The purpose of the current study was to examine the effect of uncertainty on caregivers' perceived and physiological stress (i.e., salivary cortisol). A prospective, longitudinal observational study was conducted with a convenience sample of 40 caregivers and stroke survivors recruited from acute care settings. Linear mixed models were used. Greater uncertainty was associated with higher perceived stress (p < 0.001), but not with physiological stress (p = 0.32 on waking, p = 0.06 evening), over the first 6 weeks post-stroke. A significant association between uncertainty and evening salivary cortisol level was found at 6 weeks post-stroke (p = 0.009). Recognition of uncertainty early in the caregiving period and targeted interventions may be useful in reducing perceived stress for this group. [Journal of Gerontological Nursing, 43(11), 30–40.]

Stroke is a common phenomenon worldwide and functional recovery is often dependent on caregivers (Rigby, Gubitz, & Phillips, 2009; Visser-Meily et al., 2009). Therefore, impaired health and well-being in stroke survivors' caregivers are also important public health concerns. In the United States, approximately 795,000 new or repeated strokes occur each year, and a large proportion occur in adults 65 and older (Mozaffarian et al., 2015). Older adult stroke survivors have greater disability and poorer outcomes (Russo, Felzani, & Marini, 2011). In contrast to the trajectory of caregiving for individuals with chronic disorders, the need to assume the informal caregiving role very suddenly places caregivers of stroke survivors at risk for caregiver stress associated with these new responsibilities (Byun & Evans, 2015).

Caregivers of stroke survivors report health problems such as depression, anxiety, hypertension, and angina within months to years after the stroke event (King et al., 2012; Loh, Tan, Zhang, & Ho, 2016; McLennon, Bakas, Jessup, Habermann, & Weaver, 2014; White, Mayo, Hanley, & Wood-Dauphinee, 2003). Caregivers' stress and strain have been associated with mortality and morbidity, specifically higher mortality rates in those with greater emotional strain (Schulz & Beach, 1999), increased risk for stroke in spousal caregivers reporting higher strain (Haley, Roth, Howard, & Safford, 2010), and increased coronary heart disease in female spousal caregivers (Lee, Colditz, Berkman, & Kawachi, 2003).

Perceived (i.e., self-reported) stress is typically reflected physiologically, and includes elevated neuroendocrine mediators such as cortisol and norepinephrine (Morgan et al., 2002). Acute stress is associated with a disruption in circadian rhythms (Févre Montange et al., 1981) and elevated levels of plasma and salivary cortisol (Morgan et al., 2002). In a study of adults exposed experimentally to a stressor and whose spouses experienced progressive dementia, caregivers (compared to non-caregivers) had greater evidence of sympathetic activation, with higher blood pressures and heart rates (Cacioppo et al., 2000). However, it is not known whether stress hormones are elevated in caregivers experiencing acute stress associated with a family member's sudden and serious health event.

Uncertainty occurs when decision makers cannot determine meaning for illness-related events or predict what will happen next or the consequences from the event due to lack of information (Mishel, 1997a). Uncertainty can be perceived as either danger or opportunity (Mishel, 1997a). When perceived as danger, people cope by trying to adapt to the situation and thereby resolve uncertainty (Mishel, 1997a). Uncertainty associated with a family member's sudden and serious health event (i.e., stroke) may be a factor in better understanding the caregiving experience and its negative health sequelae in this and related populations. Thus, the purpose of the current study was to examine the effect of uncertainty on caregiver perceived and physiological stress during the first 6 weeks post-stroke. It was hypothesized that greater uncertainty would be positively associated with higher levels of perceived and physiological stress.

Method

A prospective, longitudinal observational study was conducted with a convenience sample of caregivers and their stroke-survivor relatives recruited from acute care settings in two Philadelphia academic health-science centers. Institutional review boards from both recruitment sites approved the study and all participants provided written informed consent. Caregivers were enrolled at the hospital within the first 2 weeks following their relatives' stroke (baseline: T1) and revisited 1 month later (4 to 6 weeks post-stroke: T2). Measuring uncertainty, perceived stress, salivary cortisol, and selected covariates in a natural clinical environment allowed examination of changes over time that occurred in the early weeks of the post-stroke period. Further, by 4 to 6 weeks following the event, stroke survivors are more likely to have been discharged (to home, rehabilitation hospitals, or nursing facilities) and family caregivers to be more directly involved in their care. Informed consent and Health Insurance Portability and Accountability Act of 1996 (HIPAA) authorization to access stroke survivors' medical records and collect relevant health information were obtained from stroke survivors or their surrogates.

Sample

Inclusion criteria were: (a) self-identify as a family member and expected primary caregiver for an older adult (65 or older) who had been diagnosed within the past 2 weeks with new or recurrent ischemic or hemorrhagic stroke, (b) able to communicate in English, (c) able to demonstrate capacity for informed consent, and (d) age 21 or older.

Study Variables and Instruments

Uncertainty. Uncertainty was measured using the 31-item Mishel Uncertainty in Illness Scale for Family Members (Mishel, 1997b). Items illustrate a caregiver's inability to determine the meaning of illness-related events (Mishel, 1997a), and each is scored on a scale of 1 (strongly disagree) to 5 (strongly agree). Total sum scores range from 31 to 155; higher scores indicate greater uncertainty. Internal consistency for the total scale was 0.81 to 0.92 (Cronbach's alpha) for family caregivers (Mishel, 1997b); in the current study, Cronbach's alpha was 0.92 at T1 and 0.95 at T2.

Stress. Perceived stress was measured by the Perceived Stress Scale (Cohen, Kamarck, & Mermelstein, 1983), which includes 14 items designed to assess symptoms of stress and global measures of the degree of stress experienced in the past month. In the current study, the time parameter was modified to ask about stress experienced in the past day (24 hours) because at T1 the past month would have preceded the relative's stroke. Each item is scored from 0 (never) to 4 (very often), with total sum scores ranging from 0 to 56; higher scores indicate higher perceived stress. Cronbach's alpha of the scale ranges from 0.84 to 0.86 (Cohen et al., 1983), and was 0.91 for older African American and European American females (McCallum, Sorocco, & Fritsch, 2006). In the current study, Cronbach's alpha was 0.86 at T1 and 0.88 at T2.

Physiological stress was measured by salivary cortisol, which has been shown to reliably assess the variation in endocrine activity and response to acute stress (Févre Montange et al., 1981). Salivary cortisol is highly correlated with serum cortisol: correlation coefficients range from 0.71 in patients with alpha-cholinergic medication to 0.96 in healthy older adults (Kirschbaum & Hellhammer, 1994). Cortisol levels follow a circadian rhythm (Préville, Zarit, Susman, Boulenger, & Lehoux, 2008); levels normally reach their peak in the early morning and the concentration is lower at night (Chernow et al., 1987). In some samples, cortisol levels measured in the morning (9:00 a.m.) and afternoon (4:00 p.m.) have not coincided with a normal circadian rhythm pattern, whereas peak levels on waking and lower levels in the evening were found generally consistent across samples (Woods et al., 2008). To capture diurnal variations in cortisol concentration in the current study, caregivers collected saliva using Salimetrics® oral swabs on waking and again at 9:00 p.m. (McCallum et al., 2006). Caregivers were instructed not to eat food, drink liquid, or brush teeth for 30 minutes before and not to smoke for 60 minutes before collecting saliva. An inter-assay coefficient of variation was 6.56% and intra-assay coefficient of variation was 4.61%, indicating good precision, and the minimal detection limit distinguishable from 0 was 0.01 µg/dL.

Sociodemographic and Clinical Characteristics. Caregiver characteristics and stroke survivor characteristics, supported by previous literature on stress in caregivers of stroke survivors, were selected for measurement. Sociodemographic characteristics such as age, gender, race, education, and income were collected. Participants were asked to rate their household income as comfortable, have more than enough to make ends meet; adequate, have enough to make ends meet; or do not have enough to make ends meet. Other caregiver characteristics included smoking (yes/no), comorbidity, coping capacity, and social support. Comorbidity was assessed using a modified version of the Cumulative Illness Rating Scale (Miller et al., 1992), with higher scores indicating more comorbid illness. A 13-item short-form version of the Sense of Coherence tool (Antonovsky, 1987) was used to measure how well caregivers perceived they coped with stress associated with caregiving; higher scores indicated greater coping. Cronbach's alpha for the Sense of Coherence tool was 0.83 at T1 and 0.90 at T2. Social support was measured using the Multidimensional Scale of Perceived Social Support (Zimet, Dahlem, Zimet, & Farley, 1988), with higher scores indicating better levels of perceived social support. Cronbach's alpha was 0.94 at T1 and T2. All caregiver characteristics were assessed at T1 and the following were re-assessed at T2: Mishel Uncertainty in Illness Scale for Family Members, Perceived Stress Scale, salivary cortisol, Cumulative Illness Rating Scale, Sense of Coherence tool, Multidimensional Scale of Perceived Social Support, hours spent caring per day, and other life events.

Sociodemographic characteristics (e.g., age, education, occupation, location at T2 [e.g., home, rehabilitation hospital, nursing facility] to which the stroke survivor was transferred following hospital discharge and site of current placement) of stroke survivors were also collected. Other stroke survivor characteristics at T1 included severity of stroke, description of stroke (e.g., type, area), and comorbidity—all obtained from chart review an average of 4.63 days (SD = 3.74 days) post-stroke. Severity of stroke was measured by the National Institutes of Health (NIH) Stroke Scale (Cronbach's alpha = 0.87). Total scores ranged from 0 (not impaired) to 42 (fully impaired). The Cumulative Illness Rating Scale (Miller et al., 1992) used for caregivers was also used to assess comorbidity in stroke survivors. At T1 and T2, caregiver perception of functional status was assessed using the Barthel Index (Mahoney & Barthel, 1965), with higher scores indicating independence from help. Cronbach's alpha was 0.94 at T1 and 0.95 at T2.

Statistical Analysis

Data were analyzed using SPSS version 22 and Stata® 13. Descriptive statistics were used to report uncertainty, perceived and physiological stress, and sociodemographic and stroke-related data (means, standard deviations, and frequencies). Paired t tests (for continuous variables) and McNemar tests (for categorical variables) were used to explore changes over time in variables measured at T1 and T2. Associations of variables collected only at T2 (e.g., site of current placement of stroke survivors, such as home) were evaluated using analyses of variance with post hoc tests. Spearman correlations were also used to explore relationships among uncertainty, perceived stress, and salivary cortisol at both time points.

Given the large number of variables available and limited sample size, a separate unadjusted linear mixed model was computed to examine the relationship between uncertainty and repeated measures of stress (perceived stress or physiological stress) without adjustment for other variables. In addition, a separate unadjusted linear mixed model was computed to examine the relationship between each caregiver or stroke survivor characteristic and repeated measures of stress (perceived stress or physiological stress) without adjustment for other variables. Full maximum likelihood with random intercept at level 2 was used. Each independent variable was either time-varying (values for variables measured at both time points [e.g., uncertainty]) or fixed (values for variables measured only at baseline [e.g., gender]). Each model included one independent variable (e.g., uncertainty, age) and time variable (i.e., T1 and T2) to determine whether uncertainty or each caregiver or stroke survivor characteristic was independently associated with either perceived or physiological stress. For all analyses, a p value <0.05 in a two-sided test was considered statistically significant.

Results

A convenience sample of 63 caregivers and stroke survivors was enrolled. However, by T2, 13 stroke survivors had died; three caregivers had withdrawn from the study and seven more were lost to follow up despite multiple attempts made to contact them. Thus, 40 caregivers with data for T1 and T2 were available for analysis. No survey data were missing for these caregivers. Thirty-eight caregivers provided saliva samples on waking and in the evening. Of the evening samples at T1, one extreme outlier when assayed suggested contamination and was excluded from data analysis. The medical records of 40 stroke survivors were reviewed, with no missing data. Comparing baseline characteristics of participants who completed the study (N = 40) and those not included in the data analysis (n = 23), there were no significant differences with these exceptions: non-completers had more social support at baseline (p = 0.036) and they and their stroke survivors were more likely to be non-Hispanic, White individuals (p = 0.018 for caregivers and 0.009 for stroke survivors).

Caregiver and Stroke Survivor Characteristics

Caregiver and stroke survivor sociodemographic characteristics are presented in Table 1. Mean age of caregivers was 57.7 years (SD = 14.22 years) and approximately 30% were 65 or older. Most caregivers were women (67.5%) and non-Hispanic, White (62.5%) or African American (30%) individuals.

Characteristics and Demographics of Caregivers and Stroke Survivors (N = 40)Characteristics and Demographics of Caregivers and Stroke Survivors (N = 40)

Table 1:

Characteristics and Demographics of Caregivers and Stroke Survivors (N = 40)

Mean age of stroke survivors was 75.6 years (SD = 7.8 years, range = 65 to 95 years). For most stroke survivors (80%), the stroke that occurred was their first (Table 1). Approximately 60% of the sample was initially discharged from the acute care hospital to a rehabilitation hospital (22.5% to home, 10% to a nursing facility, and 7.5% to another place or remained hospitalized). When caregivers were interviewed at T2, 43% were at home versus 27.5% at a rehabilitation hospital, 12.5% at a nursing facility, and 17.5% at another place.

Study variables collected at both time points are presented in Table 2. By T2, caregivers had better coping capacity, but reported more comorbidities and less social support. Stroke survivors' functional status improved from T1 to T2. The diurnal variations in cortisol concentration are shown in the Figure. A correlation matrix of uncertainty, perceived stress, and salivary cortisol is presented in Table 3.

Comparison of Study Variables between Baseline (T1) and 6 Weeks Post-Stroke (T2) (N = 40)

Table 2:

Comparison of Study Variables between Baseline (T1) and 6 Weeks Post-Stroke (T2) (N = 40)

Diurnal salivary cortisol pattern at T1 and T2.

Figure.

Diurnal salivary cortisol pattern at T1 and T2.

Spearman Correlation Matrix of Caregiver Uncertainty, Perceived Stress, and Salivary Cortisol

Table 3:

Spearman Correlation Matrix of Caregiver Uncertainty, Perceived Stress, and Salivary Cortisol

Uncertainty and Characteristics Associated With Stress

The unadjusted linear mixed model examining the association between uncertainty and repeated measures of perceived stress is presented in Table 4. Greater uncertainty was associated with higher perceived stress (p < 0.001). However, time was not associated with repeated measures of perceived stress (p = 0.789), indicating there was no change in the level of perceived stress by 6 weeks post-stroke and that caregivers experienced stress consistently over the first 6 weeks post-stroke. Each unadjusted linear mixed model with significant associations between a caregiver or stroke survivor characteristic and repeated measures of perceived stress is presented. In separate models, each of the following characteristics was independently associated with caregiver higher perceived stress across the first 6 weeks post-stroke: caregiver's income; poorer coping capacity; more comorbidities; less social support; number of close friends and relatives; and stroke survivor's gender, income, insurance type, and poorer functional status.

Uncertainty and Characteristics Associated with Stress Based on Unadjusted Linear Mixed Models (N = 40)Uncertainty and Characteristics Associated with Stress Based on Unadjusted Linear Mixed Models (N = 40)

Table 4:

Uncertainty and Characteristics Associated with Stress Based on Unadjusted Linear Mixed Models (N = 40)

Uncertainty was not significantly associated with repeated measures of salivary cortisol either on waking (p = 0.32) or in the evening (p = 0.06). In the bivariate analysis using Spearman's correlation coefficient calculation at T2, higher uncertainty (r = 0.418, p = 0.009) and higher perceived stress (r = 0.520, p = 0.001) were correlated with elevated salivary cortisol levels in the evening. Other predictors of repeated measures of salivary cortisol are described in Table 4. Spousal (versus non-spousal) relationship with the stroke survivor and stroke survivor's intra-cerebral hemorrhage (versus ischemic stroke) were independently associated with higher caregiver salivary cortisol levels in the morning. Caregivers' insufficient (versus comfortable) income was also associated with elevated salivary cortisol levels in the evening.

Discussion

The purpose of the current study was to examine the effect of uncertainty on caregivers' perceived and physiological stress during the first 6 weeks post-stroke. Baseline levels of uncertainty and perceived stress were higher than reported in other caregiver populations (Mishel, 1997b; Mitchell & Courtney, 2004; Schwarz & Dunphy, 2003) and remained high at 6 weeks post-stroke. Physiological stress remained consistent at T1 and T2. Greater uncertainty was longitudinally associated with higher perceived stress during the first 6 weeks post-stroke. Uncertainty was not associated with repeated measures of physiological stress across the first 6 weeks post-stroke, but a significant association was found between uncertainty and evening salivary cortisol level at 6 weeks post-stroke. Caregivers with greater uncertainty may be at risk for developing perceived and physiological stress. It is important to assess and address areas of uncertainty in the early period of caregiving after stroke as a potential stress-reduction measure.

Stroke is a complex condition with the potential for subsequent physical, psychological, and cognitive disabilities. Elevated and persistently higher levels of uncertainty and perceived stress in caregivers may reflect the suddenness of the change in their family member's health status due to stroke and the need to adjust to a major alteration in their relationship with the stroke survivor (Byun, Riegel, Sommers, Tkacs, & Evans, 2016). Although a mother's uncertainty about infant HIV serostatus has been found to be correlated with her perceived stress (Shannon & Lee, 2008), the relationship between uncertainty and stress in caregivers for stroke survivors has not been well studied. The finding of high levels of uncertainty that were sustained over a 4-week period sheds new light on this factor in terms of its relationship to stress.

In the current study, caregiver's income, poorer coping capacity, more comorbidities, less social support, and number of close friends and relatives, as well as stroke survivors' gender, income, insurance type, and poorer functional status, were each independently associated with perceived stress. Most factors associated with higher perceived stress were consistent with results reported by Ostwald, Bernal, Cron, and Godwin (2009), who identified several factors affecting perceived stress: being female, younger age, poor health status, poor coping strategies/capacity, less social support, less preparedness for caregiving, and lower number of close family and friends, as well as poor stroke survivor functional status. One possible reason for differences in factors associated with perceived stress may be that the time period explored (i.e., the first 6 weeks of caregiving) represents only the early period of caregiving, whereas Ostwald et al. (2009) investigated perceived stress in caregivers on hospital discharge of their relative and then up to 12 months post-discharge.

Uncertainty was not a predictor of repeated measures of physiological stress. A previous study reported that younger age in female caregivers of stroke survivors was associated with lower levels of cortisol on waking and 30 minutes post-waking (Saban, Mathews, Bryant, O'Brien, & Janusek, 2012). However, in the current study, a significant correlation between caregiver uncertainty and evening salivary cortisol level was found at 6 weeks post-stroke but not at baseline. It may be that although caregivers were uncertain regarding the outcomes of the stroke and their new caregiver role at baseline, the influence on physiological stress was not yet measurable within the first few days of stroke. By 6 weeks post-stroke, unabated high levels of uncertainty may have begun to influence physiological regulatory mechanisms. One possible explanation for the differences across time is that although physiological homeostasis may have been maintained at baseline, even in the face of high levels of perceived stress, the body's failure to compensate long-term led to a physiological stress response by 6 weeks post-stroke. Acute stress response, which would be represented by an increase in salivary cortisol (Morgan et al., 2002) among caregivers of stroke survivors, may be more likely detected in evening salivary cortisol levels. Further, the importance of the relationship between perceived stress and evening salivary cortisol is supported by other studies of acute stress (Woods et al., 2008).

It is not clear why the current results were inconsistent with existing literature for other study variables that were related to salivary cortisol levels on waking and in the evening (e.g., relationship to the stroke survivor, type of stroke, caregiver income). Some studies reported no correlation between perceived stress and cortisol or no change in patterns of cortisol after intervention (Deechakawan, Cain, Jarrett, Burr, & Heitkemper, 2013; Williams et al., 2010). Cortisol levels and diurnal slopes can vary depending on chronicity (Fries, Hesse, Hellhammer, & Hellhammer, 2005) and age (Saban et al., 2012). Severity of comorbidities and smoking history that would potentially impact cortisol levels were also assessed; however, these were not associated with salivary cortisol. The current findings warrant further research on physiological stress (salivary cortisol) using repeated measures in a larger sample to better understand the mixed results.

In the current study, caregivers reported slightly better coping capacity, but more comorbidities and lower levels of social support, at 6 weeks post-stroke compared to baseline. Caregivers felt uncertain in the early weeks of caregiving and their health began to deteriorate. Thus, it is important to monitor caregivers in the early periods after stroke, especially older spousal caregivers who may have existing health problems (Byun et al., 2016).

Greater caregiver involvement in discharge planning for stroke survivors may help reduce early uncertainty and support decision making in care planning in the complex and often alienating health care delivery system during this critical period. Anticipatory guidance and the provision of information about care needs and care options may enhance caregiver preparedness and reduce uncertainty. Caregivers for patients with heart failure have better caregiving experiences and health outcomes when they are involved in hospital discharge planning (Bull, Hansen, & Gross, 2000). Efforts to enhance social support during discharge planning for stroke survivors and their caregivers may help forestall untoward outcomes.

Strengths and Limitations

Strengths of the current study include use of perceived and physiological measures of stress. Other strengths include a longitudinal design and a relatively ethnically diverse sample. Limitations of the study include convenience sampling from a single geographic region, the relatively small sample, and a higher than desired attrition rate (38%) due to the high death rate of stroke patients. Due to the sample size, other caregiver or stroke survivor characteristics were not controlled in a single linear mixed model. Medications (e.g., steroid-based drugs) may have affected cortisol levels, but caregivers' medications were not assessed. The term “close” was also not defined when assessing “number of close friends” in caregivers. In future studies, the meaning of “close relatives and friends” (e.g., emotionally or geographically) must be clarified to better identify the availability of instrumental and social support for caregivers.

In addition, recurrent stroke was not associated with perceived or physiological stress, although both first and recurrent strokes have a sudden onset and, thus, outcome is not immediately known. Further studies with larger samples are required to differentiate stress between caregivers of survivors with first and recurrent strokes. No other stroke survivor characteristic, such as severity of stroke, stroke survivor comorbidity, or communication disabilities, was associated with caregiver uncertainty. Stroke survivor placement location at 6 weeks post-stroke did not influence caregiver perceived or physiological stress at that same observation point, despite the likelihood that those referred to home may have had a less severe stroke. Caregiver stress may be more influenced by perception of stroke survivor status rather than objectively assessed status, such as severity of stroke measured by the NIH stroke scale. Assuring adequate statistical power and rigorous assessment of additional caregiver and stroke survivor characteristics that can affect stress (e.g., caregivers' medications) in a larger and longer study will be the first step to target stress prevention and reduction in this at-risk population.

Conclusion

In the current study, uncertainty was longitudinally associated with perceived stress during the first 6 weeks post-stroke, despite improvement in stroke survivor functioning. Uncertainty was not longitudinally associated with overall physiological stress during the first 6 weeks post-stroke, but higher uncertainty was associated with elevated salivary cortisol levels at 6 weeks post-stroke. Recognition of uncertainty early in the caregiving period may be useful in identifying at-risk caregivers in need of additional support. Given the poor health outcomes known to be related to prolonged high levels of stress, targeted interventions aimed at resolving uncertainty may also reduce stress and, thus, help preserve health and functioning in these caregivers (Byun et al., 2016). The current findings suggest potential for the development and testing of novel strategies to provide more immediate support to family caregivers, especially those whose caregiving role and whose relative's health state have suddenly and radically changed.

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Characteristics and Demographics of Caregivers and Stroke Survivors (N = 40)

VariableMean (SD)
CaregiversStroke Survivors
Age (years)57.7 (14.22)75.6 (7.8)
No. of close friends and relatives18.83 (18.71)
Days post-stroke at T1 interview4.63 (3.74)
Severity of strokea11.43 (9.74)
Comorbidity scoreb8.68 (5)
n (%)
Gender
  Female27 (67.5)25 (62.5)
  Male13 (32.5)15 (37.5)
Race/ethnicity
  White25 (62.5)24 (60)
  African American12 (30)13 (32.5)
  Other3 (7.5)3 (7.5)
Health insurance
Private/Medicare/Medicare and supplemental health insurance35 (87.5)33 (82.5)
  Medicare and Medicaid/Medicaid/no insurance5 (12.5)7 (17.5)
Education
  Less than high school0 (0)6 (15)
  High school14 (35)16 (40)
  Vocational training5 (12.5)4 (10)
  College15 (37.5)10 (25)
  Postgraduate6 (15)4 (10)
Employment
  Full-time14 (35)1 (2.5)
  Retired13 (32.5)31 (77.5)
  Part-time5 (12.5)1 (2.5)
  Unemployed4 (10)1 (2.5)
  Leave of absence3 (7.5)0 (0)
  Homemaker1 (2.5)6 (15)
Incomec
  Comfortable21 (52.5)16 (40)
  Adequate14 (35)21 (52.5)
  Insufficient5 (12.5)3 (7.5)
Variablen (%)
CaregiversStroke Survivors
Relationship to stroke survivor
  Child24 (60)
  Spouse15 (37.5)
  Sibling1 (2.5)
Smoker
  No39 (97.5)
  Yes1 (2.5)
Stroke survivors' stroke-related health characteristics
  Stroke experience
    First stroke32 (80)
    Recurrent stroke8 (20)
  Type of stroke
    Ischemic20 (50)
    Intra-cerebral hemorrhage11 (27.5)
    Subarachnoid hemorrhage9 (22.5)
  Area of stroke
    Right21 (52.5)
    Left14 (35)
    Right and left/other5 (12.5)
  Communication disability
    No22 (55)
    Yes14 (35)
    Unclassified4 (10)

Comparison of Study Variables between Baseline (T1) and 6 Weeks Post-Stroke (T2) (N = 40)

Variable (Range)Mean (SD)t Testp Value
T1T2
Caregiver characteristic
  Duration of caregiving (days)4.63 (3.75)36.03 (6.96)
  Time spent caring per day (hours)8.7 (6.29)7.60 (6.59)0.9540.346
  Comorbidity (0 to 56)a5.65 (4.37)6.20 (4.69)2.0540.047
  Coping capacity (13 to 91)a63.85 (12.52)67.25 (15.46)2.0610.046
  Social support (7 to 84)a71.15 (13.14)63.88 (18.18)2.5600.014
  Other life event (n, %)17 (43)9 (23)0.057
Main caregiver variable
  Uncertainty (31 to 155)a83.73 (23.47)85.23 (23.94)0.7130.480
  Perceived stress (0 to 56)a24.38 (10.15)24.48 (10.74)0.0800.936
  Salivary cortisol—a.m.b0.39 (0.23)0.33 (0.21)1.3080.199
  Salivary cortisol—p.m.b0.12 (0.1)c0.12 (0.1)0.0610.952
Stroke survivor characteristic
  Functional status (0 to 100)a26.25 (28.83)43.75 (36.56)3.2660.002

Spearman Correlation Matrix of Caregiver Uncertainty, Perceived Stress, and Salivary Cortisol

VariableUncertaintyPerceived StressSalivary Cortisol on Waking
T1 (baseline)
  Uncertainty
  Perceived stress0.584*
  Salivary cortisol on wakinga0.1180.068
  Salivary cortisol in the eveningb0.1290.0210.040
T2 (6 weeks post-stroke)
  Uncertainty
  Perceived stress0.508*
  Salivary cortisol on wakinga0.0380.201
  Salivary cortisol in the eveninga0.418*0.520*0.072

Uncertainty and Characteristics Associated with Stress Based on Unadjusted Linear Mixed Models (N = 40)

VariableBSEz Statisticp Value95% CI
Perceived stress
  Caregiver characteristic
    Model 1
      Uncertainty0.260.055.51<0.001[0.164, 0.346]
      Time−0.281.06−0.270.789[−2.36, 1.79]
    Model 2a
      Comfortable incomeReference
      Adequate income1.653.090.540.592[−4.39, 7.70]
      Insufficient income10.584.452.380.018[1.85, 19.30]
      Time0.101.290.080.935[−2.31,2.51]
    Model 3
      Coping capacity−0.490.06−7.86<0.001[−0.61, −0.37]
      Time1.771.251.420.156[−0.68, 4.22]
    Model 4
      Comorbidity0.680.302.280.022[0. 10, 1.26]
      Time−0.271.22−0.220.823[−2.67, 2.13]
    Model 5
      Social support−0.130.06−2.240.025[−0.244, −0.016]
      Time−0.851.28−0.660.507[−3.36, 1.66]
    Model 6
      No. of close friends and relatives−0.160.07−2.060.040[−0.31, −0.01]
      Time0.101.230.080.935[−2.31, 2.51]
  Stroke survivor characteristic
    Model 7
      MaleReference
      Female−6.842.93−2.340.020[−12.58, −1.10]
      Time0.101.230.080.935[−2.31, 2.51]
    Model 8a
      Comfortable incomeReference
      Adequate income8.362.872.910.004[2.73, 13.99]
      Insufficient income7.535.451.380.167[−3.14, 18.21]
      Time0.101.230.080.935[−2.31, 2.51]
    Model 9
      Private/Medicare/MedicareReference
      Medicare and Medicaid/Medicaid/no insurance−9.634.15−2.320.020[−17.77, −1.49]
      Time−1.301.24−1.050.295[−3.74,1.13]
    Model 10
      Functional status−0.080.03−2.820.005[−0.14, −0.03]
      Time1.561.341.160.246[−1.07, 4.19]
Salivary cortisol on waking
  Caregiver characteristic
    Model 1
      Uncertainty0.0010.0010.990.323[−0.001, 0.003]
      Time−0.0600.04−1.400.161[−0.14, 0.02]
    Model 2
      Non-spouseReference
      Spouse0.160.053.040.002[0.06, 0.27]
      Time−0.060.04−1.330.185[−0.14, 0.03]
  Stroke survivor characteristic
    Model 3
      Ischemic strokeReference
      Intra–cerebral hemorrhage0.120.061.970.049[0.00, 0.24]
      Subarachnoid hemorrhage−0.070.07−1.120.262[−0.20, 0.06]
      Time−0.060.04−1.330.185[−0.14, 0.03]
Salivary cortisol in the evening
  Caregiver characteristic
    Model 1
      Uncertainty0.0010.001.880.06[−0.00, 0.001]
      Time−0.0010.02−0.050.96[−0.05, 0.04]
    Model 2a
      Comfortable incomeReference
      Adequate income0.0030.020.120.901[−0.04, 0.05]
      Insufficient income0.110.033.220.001[0.04, 0.17]
      Time0.0020.020.100.924[−0.04, 0.04]
Authors

Dr. Byun is Assistant Professor, School of Nursing, University of Washington, Seattle, Washington; and Dr. Riegel is Professor of Nursing and Edith Clemmer Steinbright Chair of Gerontology, Dr. Sommers is Professor Emerita of Nursing, Dr. Tkacs is Associate Professor Emerita of Nursing, and Dr. Evans is Professor Emerita of Nursing, School of Nursing, University of Pennsylvania, Philadelphia, Pennsylvania.

Dr. Byun received post-doctoral funding from the National Institutes of Health (NIH)/National Institute of Nursing Research (NINR) (T32 NR007088) and 2015 University of California San Francisco School of Nursing Bridge Funding Award. The remaining authors have disclosed no potential conflicts of interest, financial or otherwise. This study was supported by grants from the John A. Hartford Foundation's National Hartford Centers of Gerontological Nursing Excellence Award Program; NIH/NINR (T32NR009356); Neuroscience Nursing Foundation; Sigma Theta Tau International Xi Chapter; and the Frank Morgan Jones Fund.

Address correspondence to Eeeseung Byun, PhD, RN, Assistant Professor, School of Nursing, University of Washington, 1959 NE Pacific Street, Box 357266, Seattle, WA 98195; e-mail: ebyun@uw.edu.

Received: November 29, 2016
Accepted: May 18, 2017
Posted Online: June 26, 2017

10.3928/00989134-20170623-02

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