Abstract
As an occupational therapy intervention, comprehensive ADL training could be crucial for stroke survivors who are preparing to return to their community from a clinical setting.
In Korea, the number of patients with stroke reached 120,000 in 2021 (Korean Statistical Information Service, 2021). Stroke is a clinically defined syndrome of neurological deficits caused by damage to the blood vessels of the central nervous system (Murphy & Werring, 2020). Stroke is associated with a decline in health-related quality of life (QoL). Abubakar and Isezuio (2012) reported that lower stroke severity was associated with improved health-related QoL. Carod-Artal et al. (2000) identified key factors determining the QoL in stroke survivors, including neurological impairment severity. Cerniauskaite et al. (2012) demonstrated that cerebrovascular disease, particularly severe stroke, has a significant impact on a patient’s QoL, with implications for functional disability factors.
The functional impairment that has the most impact on the health-related QoL of patients with stroke is a decline in performance of their basic activities of daily living (BADLs) and instrumental activities of daily living (IADLs). The performance of activities of daily living (ADLs)—or ADL function, defined as the performance of a combination of BADLs and IADLs—is one of the most basic elements. Accordingly, ADL intervention is part of occupational therapy practice for treating patients with stroke, and several positive effects have been observed, including improvements in BADL performance, IADL performance, and social participation (Steultjens et al., 2003). Moreover, it has been reported that the rehabilitation goal desired by most patients with stroke is ADL and IADL function recovery (Waddell et al., 2016).
Functional disabilities caused by stroke can cause difficulties not only with performing ADLs but also with returning to work. Failure to return to work because of functional impairment from a stroke can create personal income challenges. Furthermore, this loss of income can impede access to rehabilitation services and slow functional recovery (Horner et al., 2003). According to a previous study, among 58 patients with stroke 1 yr after discharge, 83% still had cognitive dysfunction; 20% were dependent in performing ADLs, and 80% had a limited or minimal return to work (Ashley et al., 2019; Edwards et al., 2018; Hofgren et al., 2007; Treger et al., 2007; Wang et al., 2014). Decreased ADL function and reduced income because of stroke are associated with low QoL (Kwon et al., 2018; Li et al., 2023), which can be categorized into physical, material, social, emotional, developmental, and activity QoL (Felce & Perry, 1995). Among these, ADL function and income could be related to both physical and mental well-being. In other words, it goes beyond mere financial considerations and can also affect their psychological well-being and satisfaction. Furthermore, individuals’ or groups’ satisfaction with their income can be shaped when compared with their income expectations. Sometimes, even with a high income, if one fails to meet the higher income expectations, their satisfaction may be low. Conversely, with a lower income, if there are no high income expectations, satisfaction can be high (Clark et al., 2008; D’Ambrosio & Frick, 2007; Ferrer-i-Carbonell & Frijters, 2004). Therefore, both income and income satisfaction can serve as significant variables in the context of both physical and mental well-being.
Several studies reported relationships among ADL function, income satisfaction, and health satisfaction. Health satisfaction is a concept that typically represents a person’s satisfaction with their health-related state. This term can encompass various aspects related to physical health, mental health, and well-being (Diener et al., 1985; Khanna & Tsevat, 2007). Health satisfaction can be influenced by a multitude of factors, including personal experiences, social environments, cultural factors, and more. Kanayama et al. (2016) reported a positive relationship between ADL function and QoL in 40 patients with stroke. Katzan et al. (2018) stated a negative relationship between satisfaction with physical functioning, social role, and income. Kwon et al. (2018) noted that a decrease in the QoL of patients with stroke was related to a reduction in their income status, a decrease in subjective health status, and an increase in activity limitation.
Although previous studies reported significant relationships among ADL function, income satisfaction, and health satisfaction in patients with stroke, these studies were cross-sectional (Ho et al., 2002; Kahneman & Deaton, 2010; Kanayama et al., 2016). A major limitation of cross-section designs is that they cannot indicate causal directions among complicatedly related characteristics. Additionally, this type of research design cannot control for time-varying characteristics over time (e.g., annual income, ADL function, and income satisfaction). Therefore, for examining the effects of ADL function and income satisfaction on health satisfaction, longitudinal study designs would be appropriate. Furthermore, latent growth curve modeling approaches can be used to examine which factors influence the trajectory of health satisfaction over time by controlling for various time-invariant characteristics (e.g., baseline demographics and health behavior characteristics) and time-varying characteristics (e.g., annual income, ADL function, and income satisfaction). However, because health behavior characteristics can change over time (e.g., alcohol consumption, hypertension, diabetes), these characteristics also need to be treated as time-varying factors in latent growth curve models (LGMs). Therefore, in this study, we investigated the longitudinal effects of ADL function and income satisfaction on health satisfaction using an LGM. Our research hypotheses were that higher levels of ADL function will have a positive impact on the trajectory of health satisfaction over time in patients with stroke and that higher levels of income satisfaction will have a positive effect on the trajectory of health satisfaction over time in patients with stroke.
Method
Data Sources
We used data from longitudinal panel databases of the Korean Longitudinal Study on Aging (KLoSA) that were collected by the Korea Employment Information Service. A total of four waves from 2014 to 2020 were used. From 2006 to 2020, the KLoSA collected data from a national sample in every even-numbered year, for a total of eight waves of data being collected (Boo & Chang, 2006). The KLoSA includes information on household membership, health status, employment, income and consumption, assets, subjective expectations and QoL, and mortality rates (Boo & Chang, 2006). We extracted data of individuals with stroke from the 2014–2020 KLoSA databases. The inclusion criteria include patients with stroke and those who responded to all panel surveys from 2014 to 2022.
Dependent Variables
We used health satisfaction as the dependent variable and extracted this information from four time points of the 2014, 2016, 2018, and 2020 KLoSA databases. The KLoSA collected the health satisfaction information using the self-reported question, “How satisfied are you with your health condition?” The closer the score was to 0, the lower the satisfaction with their health condition; the closer the score was to 100, the higher the satisfaction (Boo & Chang, 2006).
Time-Varying Independent Variables for Latent Growth Curve Models 2.a and 2.b
We used two time-varying independent variables, including ADL function (Model 2.a) and income satisfaction (Model 2.b). We extracted each piece of information from the four time points of the 2014, 2016, 2018, and 2020 KLoSA databases. We measured ADL function, defined as a combination of BADL and IADL performance, by assessing the extent to which survey participants were independent in 17 daily tasks: dressing, washing and brushing, bathing or showering, eating, getting in and out of bed, using the toilet, managing bowel control, grooming, performing housework, preparing meals, performing laundry, going out using transportation, going out without using transportation, shopping, managing money, receiving calls, and managing medications. The response categories of the 17 ADL functions were dichotomized (1 = no help needed, and 0 = needed help). We used the total score of the 17 ADL tasks (scores ranged from 0 to 17 points) so that higher scores indicated better ADL function. Income satisfaction was measured using a self-reported 10-point scale; higher scores indicated higher income satisfaction (Boo & Chang, 2006).
Covariates
The baseline demographics and health behavior characteristics were used as time-invariant covariates. Baseline demographics included age (continuous), gender (1 = male, 0 = female), educational attainment (1 = elementary school, 2 = middle school, 3 = high school, 4 = college degree), employment status (1 = employed, 0 = unemployed), residential area (1 = urban, 2 = suburban, and 3 = rural), and annual income (continuous). Because the annual income was inconsistent over the years, we treated this variable as a time-varying covariate. Health behavior characteristics included alcohol consumption (1 = yes, 0 = no), hypertension (1 = having it, 0 = not having it) and diabetes (1 = having it, 0 = not having it). However, alcohol consumption, hypertension, and diabetes, which have the potential to change over time, were additionally used as time-varying independent variables in sensitivity analysis.
Statistical Analysis
We used LGM approaches to elucidate the growth path of dependent variables by estimating growth factors, including the intercept (i) representing the initial value and the slope (s) representing the rate of change over time (Muthén & Muthén, 2007). For LGM estimations, we fixed the intercept loadings at 1.0 to estimate a constant range of individual differences for the initial average value. Van Mierlo et al. (2016) suggested that health satisfaction, as a component of QoL, can vary on the basis of the level of dependence or independence in ADL among patients. Therefore, assuming that the slope loadings have a linear change, the path coefficients of the rate of change factor were fixed at 0.0, 1.0, 2.0, and 3.0 (Muthén & Muthén, 2007). First, we used an unconditional LGM to identify growth patterns in health satisfaction and examine whether the trajectory pattern was well fitted into the unconditional LGM (Model 1).
Next, we added time-varying and time-invariant covariates into the unconditional LGM and investigated the longitudinal associations between ADL function (Model 2.a; see Figure A.1 in the Supplemental Material, available online with this article at https://research.aota.org/ajot) and health satisfaction, as well as between income satisfaction and health satisfaction (Model 2.b; see Figure A.2). Moreover, we examined whether baseline demographics and health behavior characteristics affect latent growth factors (intercept i and slope s). In summary, Model 1 was used to determine how the growth pattern of health satisfaction changes over time. Next, Models 2.a and 2.b were used to examine whether time-varying ADL function and income satisfaction influence the trajectory of health satisfaction over 6 yr and whether time-invariant covariates influence individual differences in latent growth factors (intercept i and slope s) of health satisfaction.
We estimated the parameters of LGMs using maximum likelihood (Muthén & Muthén, 2007). We examined the model fit of LGMs using model fit indices, including χ2, comparative fit index (CFI), Tucker–Lewis index (TLI), root-mean-square error of approximation (RMSEA), and standardized root-mean-square residual (SRMR). For χ2, a p value of .05 or higher was considered a good fit. Additionally, the model fit was examined using the index (χ2/df), obtained by dividing the test statistic value of χ2 by the degree of freedom. A value less than 2.0 was considered a good fit (Cangur & Ercan, 2015). We considered the CFI and TLI model fit criteria with a value of ≥0.95 a good fit, and we considered the RMSEA with a value within 0.08 an acceptable fit (Bentler, 1990; Browne & Cudeck, 1993; Cangur & Ercan, 2015; Hu & Bentler, 1999; Tucker & Lewis, 1973). For SRMR, we considered values within 0.05 as an acceptable fit (Diamantopoulos et al., 2000). We used SAS, Version 9.4, for data management and the statistical program Mplus, Version 8.4, for statistical analyses (Muthén & Muthén, 2017).
Results
The demographic characteristics of the study sample are presented in Table 1. The average age was 70.68 yr (SD = 8.09), and the majority of the sample was male (n = 107; 54.04%). Most participants completed elementary school (n = 102; 51.52%) and were unemployed (n = 152; 76.77%). The urban area was the most common place of residence, with 80 stroke survivors (40.40%), followed by suburban and rural areas with 72 (36.36%) and 46 (23.23%) stroke survivors, respectively. Finally, health satisfaction increased over time from 2014 (M = 47.27, SD = 19.45) to 2020 (M = 51.01, SD = 19.82).
Participant Demographics (N = 198)
Model 1: Unconditional Latent Growth Curve Model
The estimations of the latent growth factors in the unconditional LGM and its model fit are shown in Table 2. The unconditional LGM demonstrated good model fits, including χ2(5) = 4.778, p = .443, χ2/df = 0.956, RMSEA = 0.000, CFI = 1.000, TLI = 1.000, and SRMR = 0.046. The initial average value (i) of health satisfaction with Model 1 was 46.798 (SE = 1.344, p < .001), and the rate of change (s) was 1.083 (SE = 0.506, p = .032). The rate of change (s) was 1.083, indicating that, on average, health satisfaction increased by 1.083 units per every 2 yr. The covariance of i and s was −37.591 (SE = 13.441, p = .005), indicating a negative relationship between the initial health satisfaction score and its rate of change over time. In other words, the negative correlation indicates that participants with higher baseline health satisfaction scores showed a lower slope value (less change over time) than those with lower baseline health satisfaction scores.
Model 1 Parameter Estimates for Unconditional LGM of Health Satisfaction Change Over Time
Note. Model fit: χ2(5) = 4.778, p = .443; χ2/df = 0.956; CFI = 1.000; TLI = 1.000; RMSEA = 0.000; SRMR = 0.046. β = standardized coefficient; B = unstandardized coefficient; CFI = comparative fit index; LGM = latent growth curve model; RMSEA = root-mean-square error of approximation; SRMR = standardized root-mean-square residual; TLI = Tucker–Lewis Index.
*p < .05. **p < .001.
Model 2.a: Latent Growth Curve Model for ADL Function and Health Satisfaction
The parameter estimations of Model 2.a, including the time-varying ADL functions and covariates, are depicted in Table 3. Model 2.a demonstrated marginal model fits, including χ2(47) = 66.378, p = .032; χ2/df = 1.412, RMSEA = 0.046, CFI = 0.939, TLI = 0.904, and SRMR = 0.051. We considered that Model 2.a showed a good model fit (χ2/df < 2.0), even though the p value of the χ2 value was .032.
Model 2.a Parameter Estimates for LGM of Health Satisfaction Over Time With Time-Varying (ADL Function) and Time-Invariant Covariates
Note. Model fit: χ2(47) = 66.378, p = .032; χ2/df = 1.412; CFI = 0.939; TLI = 0.904; RMSEA = 0.046; SRMR = 0.051. ADL function = performance of a combination of basic and instrumental activities of daily living; β = standardized coefficient; B = unstandardized coefficient; CFI, comparative fit index; LGM = latent growth curve model; RMSEA = root-mean-square error of approximation; SRMR = standardized root-mean-square residual; TLI = Tucker–Lewis Index.
*p < .05. **p < .001.
Model 2.a showed that the initial average value (i) of health satisfaction was 19.495 (SE = 14.548, p = .180), and the rate of change (s) was −1.390 (SE = 6.108), p = .820. Similar to the unconditional LGM, the covariance of i and s was −31.911 (SE = 12.090, p = .008). Positive relationships between ADL function and health satisfaction over time were observed (unstandardized regression coefficients ranged from 0.655 to 1.492; all ps < .05), even after controlling for the time-varying annual income and covariates (Table 3). For the time-invariant covariates in the relationship between ADL function and health satisfaction (Model 2.a in Table 3), we observed a significant difference in the initial average value (i) only in educational attainment (B = 4.523, SE = 1.335, p = .001) and employment status (B = 7.208, SE = 3.127, p = .021; Table 3).
Last, we conducted sensitivity analyses by treating health behavior characteristics (i.e., alcohol consumption, hypertension, diabetes) as time-varying covariates from 2014 to 2020. The sensitivity analysis results were consistent, indicating that the direction and significance of those variables have not changed (Table A.1).
Model 2.b: Latent Growth Curve Model for Income Satisfaction and Health Satisfaction
Similarly, the parameter estimations of Model 2.b, including the time-varying income satisfaction and time-invariant covariates, are depicted in Table 4. Furthermore, Model 2.b showed good model fits, including χ2(47) = 57.742, p = .135; χ2/df = 1.228, RMSEA = 0.034, CFI = 0.982, TLI = 0.972, and SRMR = 0.042. Model 2.b showed that the initial average value (i) of health satisfaction was 13.537 (SE = 11.117, p = .223), and the rate of change (s) was −1.622 (SE = 4.852, p = .738). Similar to the unconditional LGM and Model 2.a, this LGM also demonstrated a negative covariance between i and s, −27.268 (SE = 8.897, p = .002). Additionally, positive relationships between income satisfaction and health satisfaction over time were observed (unstandardized regression coefficients ranged from 0.501 to 0.722; all ps < .001) even after controlling for the time-varying annual income and time-invariant covariates. For the time-invariant covariates in the relationship between income satisfaction and health satisfaction (see Model 2.b in Table 4), we noted a significant difference in the initial average value (i) only in employment status, B = 6.676 (SE = 2.587, p = .010; Table 4).
Model 2.b Parameter Estimates for LGM of Health Satisfaction Over Time With Time-Varying (Income Satisfaction) and Time-Invariant Covariates
Note. Model fit: χ2(47) = 57.742, p = .135; χ2/df = 1.228; CFI = 0.982; TLI = 0.972; RMSEA = 0.034; SRMR = 0.042. β = standardized coefficient; B = unstandardized coefficient; CFI = comparative fit index; LGM = latent growth curve model; RMSEA = root-mean-square error of approximation; SRMR = standardized root-mean-square residual; TLI = Tucker–Lewis Index.
*p < .05. **p < .001.
Last, we conducted sensitivity analyses by treating health behavior characteristics (i.e., alcohol consumption, hypertension, diabetes) as time-varying covariates from 2014 to 2020. The sensitivity analysis results were consistent, indicating that the direction and significance of those variables have not changed (Table A.2).
Discussion
We investigated the association between ADL function and health satisfaction and examined the association between income satisfaction and health satisfaction in patients with stroke using even-numbered-year data from 2014 to 2020. The study findings supported our research hypotheses that higher levels of ADL functions and income satisfaction predict more favorable trajectories of health satisfaction over time in patients with stroke. These findings highlight the significance of promoting ADL function and income satisfaction as integral factors in enhancing long-term health satisfaction outcomes for stroke survivors.
We observed that ADL function and income satisfaction were positively associated with the trajectory pattern of health satisfaction. Although previous studies used cross-sectional designs, they reported similar findings (van Mierlo et al., 2016; Wang et al., 2019). For instance, van Mierlo et al. (2016) reported that ADL function was positively related to QoL in patients with stroke. Moreover, ADL function was a significant factor in the psychosocial change in this patient population (Wang et al., 2019). Further, our longitudinal study using LGMs showed that ADL function was positively associated with health satisfaction over time. Occupational therapy supports patients with stroke in successfully performing ADLs. When patients engage in independent activities and interact with their social environment in their daily lives, their health satisfaction can improve. On the basis of the results of previous studies and the findings of this current study, it can be considered that occupational therapy can contribute to improving patients’ adaptation to daily life and promoting social participation, thereby enhancing their health satisfaction. However, in contrast to the previous cross-sectional studies (van Mierlo et al., 2016; Wang et al., 2019), our LGMs demonstrated that negative correlations were noted between the initial average score of health satisfaction (intercept i) and rate of change (slope s). This negative correlation indicates that people with a higher health satisfaction score showed a slower rate of increase in their health satisfaction score over time (Muthén & Muthén, 2007). According to previous studies, people with stroke may experience rapid improvement during the initial stages of recovery; however, over time, they may encounter limitations in the pace of their recovery (Duncan et al., 1992; Hackett & Anderson, 2000; Kwakkel et al., 2006). This trend suggests a gradual decline in the health satisfaction of stroke patients, emphasizing the importance of long-term health management.
Income satisfaction could also be a significant part of health satisfaction. Our study showed that an increase in income satisfaction positively affected health satisfaction over time. Similarly, Soylu (2023) reported that income satisfaction indirectly predicted psychological, global life satisfaction, domain-specific life satisfaction (satisfaction with social, health, financial, leisure, work, and residence status), and disability status in patients with stroke and in general adults. Additionally, it has been reported that QoL in patients with stroke can be related to income satisfaction (Anđelić Bakula et al., 2011). In other words, our study findings and those of previous studies (van Mierlo et al., 2016; Wang et al., 2019) indicated that ADL function and income satisfaction could be critical components in stroke rehabilitation.
In contrast to the previous studies (Kahneman & Deaton, 2010; Ostir et al., 2008), we adjusted for time-varying annual income when we analyzed the effects of ADL function and income satisfaction on health satisfaction. We noted that ADL function and income satisfaction were positively correlated with health satisfaction over time, despite adjusting for the total annual income. It is interesting to note that a previous study indicated that low annual income does not necessarily indicate low income satisfaction (Ostir et al., 2008). For instance, regardless of economic status, positive emotion can be related to a positive aspect of ADL function, motor, and cognitive status (Ostir et al., 2008). Furthermore, a previous study examined the relationship between income and happiness among 1,000 U.S. residents and reported that high income could not necessarily buy happiness (Kahneman & Deaton, 2010). Therefore, it is deemed essential to facilitate vocational rehabilitation for people who are on the verge of reintegrating into their local communities after a stroke. Vocational rehabilitation, through the process of returning to work, not only enhances the quality of life for patients with stroke but also contributes to heightened income satisfaction merely through engagement in economic activities (Vestling et al., 2003). Furthermore, the repetitive physical activities required in the workplace have the potential to ameliorate the physical functionality of patients with stroke (Arwert et al., 2017). Therefore, it is anticipated that this will not only improve income satisfaction but also augment overall health satisfaction.
In the LGM that examined the association between ADL function and health satisfaction (Model 2.a), only educational attainment and employment status significantly influenced the initial mean score of health satisfaction. Byhoff et al. (2017) conducted a systematic review and observed a positive association between educational attainment and health. They reported that higher educational levels are frequently associated with better health outcomes and higher health satisfaction levels. Additionally, Figueredo et al. (2020) reported that a successful return to work after a health-related absence could positively affect individuals’ health satisfaction and overall well-being. Moreover, there are studies that report a relationship between educational attainment and return to work in patients with stroke (Howard et al., 1985; Treger et al., 2007). For example, patients with stroke who have lower educational attainment may face more difficulties in returning to work than those who have higher educational attainment. In summary, educational attainment and return to work in patients with stroke are critical factors that influence the initial health satisfaction level.
This study had several limitations. The study findings may not be generalized to other health conditions or other adult populations, because we focused on the health satisfaction of patients with stroke using the Korean survey database. Moreover, other limitations include potential biases and inaccuracies arising from self-reporting, including memory recall and social desirability bias, as well as the variable quality and availability of secondary data. These factors may introduce bias in reported levels of income and health satisfaction, and incomplete or inconsistent data could affect the robustness and generalizability of the results. Additionally, both health satisfaction and income satisfaction are subjective measures that can be influenced by unique individual characteristics. Therefore, future studies should consider data from different countries and objectively examine other health conditions and additional factors.
Implications for Occupational Therapy Practice
This study has shown that the health satisfaction level among stroke survivors over time is steadily influenced by ADL function and income satisfaction. The findings of this study have the following implications for occupational therapy practice: ▪ Occupational therapy would be beneficial for evaluating people at the later stages of their recovery to determine whether they would benefit from environmental modifications or assistive devices to improve their ADL function. ▪ Additionally, when establishing a treatment plan, it is important to consider improving the physical function necessary for patients with stroke to return to work. ▪ It is important for clinicians to be aware of the characteristics of functional recovery in stroke survivors, including the fact that people with a higher health satisfaction score may exhibit a slower increase in their health satisfaction score over time.
Conclusion
Our LGM approaches demonstrated the longitudinal trajectory of health satisfaction in stroke survivors and showed a positive association with both ADL function and income satisfaction. It is expected that the health satisfaction of stroke survivors could be effectively improved by intervention plans that incorporate ADL training and address income satisfaction issues. For stroke survivors who are transitioning from a hospital setting back to the community, increasing ADL function and income satisfaction through ADL-focused treatment and linkage with vocational rehabilitation could be critical.
Supplemental Material
Supplementary material for Longitudinal Association of Health Satisfaction With Functional Status and Income Satisfaction in Stroke Survivors
Supplementary material, sj-pdf-1-aot-10.5014_ajot.2024.050410.pdf for Longitudinal Association of Health Satisfaction With Functional Status and Income Satisfaction in Stroke Survivors by Sanghun Nam, Timothy A. Reistetter and Ickpyo Hong in The American Journal of Occupational Therapy
Footnotes
Acknowledgments
This work was supported by the Ministry of Education of the Republic of Korea and the National Research Foundation of Korea (NRF-2021S1A3A2A02096338).
References
Supplementary Material
Please find the following supplemental material available below.
For Open Access articles published under a Creative Commons License, all supplemental material carries the same license as the article it is associated with.
For non-Open Access articles published, all supplemental material carries a non-exclusive license, and permission requests for re-use of supplemental material or any part of supplemental material shall be sent directly to the copyright owner as specified in the copyright notice associated with the article.
