Associated Factors of QOL Among Patients and Caregivers
The full model included primary and secondary appraisals, role (patient vs. caregivers), interaction terms between role and each appraisal variable, and all confounding variables (see Table 3). We found an association between an improvement in QOL and primary appraisals (less negative appraisals of illness/caregiving [p < .0001] and fewer feelings of hopelessness [p < .05]) and secondary appraisals (having more family support [p < .0001], more frequent engagement in health behaviors [p < .001], more use of active coping strategies [p < .001], and less reliance on avoidant coping strategies [p < .0001]). The only significant interaction terms were role*benefit of illness and role*active coping strategies, indicating that the effects of the benefit of illness (p < .05) and active coping strategies on QOL varied between patients and caregivers (p < .05).
Table 3
Full multilevel model and final model of QOL with interaction terms of role and appraisal variables
| Full Model | | | Final Modal |
Effect | Estimate | SE | p-value | | | Estimate | SE | p-value |
Intercept | 85.74 | 7.42 | < .0001 | | | 75.29 | 5.40 | < .0001 |
Role (referent: caregiver) | -20.20 | 9.24 | 0.0292 | | | -8.85 | 5.64 | 0.1172 |
Primary Appraisals | | | | | | | | |
Appraisal of illness/caregiving† | -7.63 | 1.32 | < .0001 | | | -6.48 | 0.78 | < .0001 |
Uncertainty† | -0.22 | 0.14 | 0.1170 | | | -0.28 | 0.10 | 0.0057 |
Hopelessness† | -0.42 | 0.16 | 0.0115 | | | -0.41 | 0.15 | 0.0047 |
Benefit of illness‡ | 0.79 | 0.81 | 0.3283 | | | 0.66 | 0.77 | 0.3912 |
Secondary Appraisals | | | | | | | | |
Family support‡ | 3.68 | 0.89 | < .0001 | | | 3.48 | 0.76 | < .0001 |
Dyadic illness-related communication‡ | -0.07 | 0.04 | 0.0918 | | | -0.05 | 0.03 | 0.1264 |
Health behaviors‡ | 0.24 | 0.06 | 0.0002 | | | 0.32 | 0.05 | < .0001 |
Self-efficacy‡ | 0.02 | 0.02 | 0.3206 | | | 0.04 | 0.02 | 0.0116 |
Coping strategies | | | | | | | | |
Active coping strategies‡ | 3.62 | 1.04 | 0.0005 | | | 2.87 | 0.99 | 0.0037 |
Avoidant coping strategies† | -9.67 | 1.28 | < .0001 | | | -7.78 | 0.84 | < .0001 |
Confounding Variables | | | | | | | | |
Age | 0.16 | 0.03 | < .0001 | | | 0.16 | 0.03 | < .0001 |
Gender (referent: female) | -0.96 | 0.69 | 0.1646 | | | -1.13 | 0.68 | 0.0942 |
Race (referent: non-White) | 1.84 | 0.92 | 0.0477 | | | | | |
Education | -0.18 | 0.14 | 0.1877 | | | | | |
Income (referent: <=$50,000) | 1.79 | 0.82 | 0.0289 | | | 1.56 | 0.70 | 0.0267 |
Type of relationship (referent: non-spouse) | -1.22 | 0.88 | 0.1657 | | | | | |
Symptom distress | -0.51 | 0.06 | < .0001 | | | -0.54 | 0.06 | < .0001 |
Type of cancer (referent: breast cancer) | | | | | | | | |
Colorectal cancer | -1.08 | 0.92 | 0.2424 | | | | | |
Lung cancer | -0.88 | 0.89 | 0.3261 | | | | | |
Prostate cancer | 1.36 | 1.15 | 0.2357 | | | | | |
Interaction Terms | | | | | | | | |
Role * Appraisal of illness/caregiving | 1.43 | 1.59 | 0.3694 | | | | | |
Role * Uncertainty | -0.11 | 0.20 | 0.5831 | | | | | |
Role * Hopelessness | 0.40 | 0.23 | 0.0772 | | | 0.43 | 0.18 | 0.0173 |
Role * Benefit of illness | 2.34 | 1.17 | 0.0456 | | | 2.75 | 1.12 | 0.0145 |
Role * Family support | 0.86 | 1.28 | 0.5014 | | | 1.61 | 0.93 | 0.0844 |
Role * Dyadic illness-related communication | 0.05 | 0.06 | 0.4179 | | | | | |
Role * Health behaviors | 0.15 | 0.09 | 0.1020 | | | | | |
Role * Self-efficacy | 0.03 | 0.03 | 0.3415 | | | | | |
Role * Coping strategies | | | | | | | | |
Role * Active coping strategies | -3.37 | 1.43 | 0.0188 | | | -2.28 | 1.33 | 0.0878 |
Role * Avoidant coping strategies | 2.96 | 1.66 | 0.0749 | | | | | |
Note: |
1. The coefficient of determination (R2) values of the full model and final model are 0.7478 and 0.7414, respectively. |
2. The p-value of the likelihood-ratio test comparing the full model and final model is 0.0748. |
3. †: Higher scores indicated more negative results, i.e., more negative appraisal of illness/caregiving as a threat, more feelings of uncertainty and hopelessness, and more avoidant coping strategies adopted (e.g., alcohol or drug use). |
4. ‡: Higher scores indicated more positive results, i.e., more benefit of illness, more family support, better dyadic illness-related communication, more frequent engagement in health behaviors, and more active coping strategies adopted (e.g., getting advice or help). |
Additionally, for patients and caregivers, better QOL had a significant correlation with older age (p < .0001), being White (p < .05), having an income above $50,000 (p < .05), and experiencing less symptom distress (p < .0001). The role effect demonstrated statistical significance (p < .05), indicating that patients had significantly lower QOL than their caregivers when considering appraisals and confounders. We found no significant difference in the association between QOL and type of cancer.
In this full model, the coefficient of determination (R2) value was 0.7478, indicating that the primary and secondary appraisals can explain about 74.78% of the variance in QOL after controlling for the confounders.
(Insert Table 3 here)
To obtain the final model, guided by the adapted stress-coping model, we conducted a stepwise elimination process for variables with the largest p-values in each model, which indicated the smallest effect on QOL (See Table 4). Initially, we focused on confounding variables, starting with the type of cancer. Removing it did not result in a significant difference between the full model and the reduced model (p > .05), allowing us to proceed with removing the type of relationship, education, and race, none of which showed significant differences (p > .05). However, the removal of gender yielded a significant difference between the full model and the resulting reduced model (p < .05), necessitating its retention in the model (fm4). Subsequently, we evaluated interaction terms. We removed six interaction terms until role*active coping strategies cannot be removed (fm11). Lastly, we assessed the main effects of appraisal variables. The removal process was halted when the first variable, dyadic illness-related communication, resulted in a significant difference (p < .05), indicating it needed to be retained in the final model (fm11).
Table 4
Step-by-step procedures of model selection
| Variables | ANOVA Chi-Square | Degree of Freedom | P-Value† | R2 | Results | Model Selected |
Confounding Variables | |
1 | Type of cancer | 5.84 | 3 | 0.1198 | 0.7472 | Type of cancer is removed. | Fm1 |
2 | Type of relationship | 7.37 | 4 | 0.1178 | 0.7472 | Type of relationship is removed. | Fm2 |
3 | Education | 9.30 | 5 | 0.0978 | 0.7463 | Education is removed. | Fm3 |
4 | Race | 12.31 | 6 | 0.0555 | 0.7448 | Race is removed. | Fm4 |
5 | Gender | 15.67 | 7 | 0.0283* | 0.7457 | Gender needs to be kept. | Fm4 |
After removing “gender,” a significant difference is observed between the full model and model fm4 (ρ < .05); therefore, “gender” and other remaining confounding variables need to be kept in the final model. Confounding variables of type of cancer, type of relationship, education, and race are removed from the model. The selection of confounding variables stops. | |
Interaction Terms | |
6 | Role*uncertainty | 12.55 | 7 | 0.0838 | 0.7449 | Role*uncertainty is removed. | Fm6 |
7 | Role* dyadic illness-related communication | 13.18 | 8 | 0.1058 | 0.7444 | Role*dyadic illness-related communication is removed. | Fm7 |
8 | Role*appraisal of illness/caregiving | 13.94 | 9 | 0.1245 | 0.7438 | Role*appraisal of illness/caregiving is removed. | Fm8 |
9 | Role*self-efficacy | 14.76 | 10 | 0.1409 | 0.7434 | Role*self-efficacy is removed. | Fm9 |
10 | Role*avoidant coping strategies | 16.98 | 11 | 0.1085 | 0.7414 | Role*avoidant coping strategies is removed. | Fm10 |
11 | Role*health behaviors | 19.61 | 12 | 0.0748 | 0.7414‡ | Role*health behaviors is removed. | Fm11 |
12 | Role*active coping strategies | 22.61 | 13 | 0.0467* | 0.7394 | Role*active coping strategies needs to be kept. | Fm11 |
After removing “role*active coping strategies”, a significant difference is observed between the full model and model fm11 (ρ < .05); therefore, “role*active coping strategies” and other remaining interaction terms need to be kept in the final model. Interaction terms of role*uncertainty, role*dyadic illness-related communication, role*appraisal of illness/caregiving, role*self-efficacy, role*avoidant coping strategies, and role*health behaviors are removed from the model. The selection of interaction terms stops. | |
Main Effects of the Appraisal Variables | |
13 | Dyadic illness-related communication | 24.84 | 14 | 0.0362 | 0.7379 | Dyadic illness-related communication needs to be kept. | Fm11 |
After removing “dyadic illness-related communication,” a significant difference is observed between the full model and model fm11 (ρ < .05); therefore, “dyadic illness-related communication” and other main effects of the appraisal variables need to be kept in the final model. No main effect of the appraisal variable is removed from the model. The model selection stops. Fm11 is selected as the final model. | |
Note: |
1. †: ρ-value is the result of the likelihood-ratio test comparing the full and selected models. |
2. ‡: R2 is 0.7414 for the final model, which is fm11, indicating the variables in the final model explained 74.14% of the variance in the QOL of patients with advanced cancer and their caregivers. |
3. *: The p-values of the likelihood-ratio test comparing the full model and selected models are < 0.05, and the model selection for that group of variables is complete. |
(Insert Table 4 here)
As we closely followed the model selection procedures, we observed that removing a variable affected the effects of the remaining variables on the QOL. For example, although race had a significant effect on QOL in the full model (see Table 3), it was removed in Step 4 due to its conditional independence on QOL, given the other remaining variables (see Table 4). This indicated that race appeared significant only when all variables were considered together but became non-significant in fm4. Similarly, role*active coping strategies was significant in the full model but non-significant in fm11. However, it remained in the final model (fm11) because removing it at Step 12 showed a significant difference between the full model and the resulting reduced model. The step-by-step model selection ensured the model's goodness of fit and simplicity.
The final model revealed an association between QOL improvement and primary appraisals (less negative appraisals of illness/caregiving [p < .0001] and fewer feelings of uncertainty [p < .01] and hopelessness [p < .01]) and secondary appraisals (having more family support [p < .0001], more frequent engagement in health behaviors [p < .0001], higher level of self-efficacy [p < .05], more use of active coping strategies [p < .01], and less reliance on avoidant coping strategies [p < .0001]).
The only significant interaction terms were role*hopelessness and role*benefit of illness (see Fig. 2), indicating that the associations between QOL and hopelessness and the benefit of illness varied between patients and caregivers. A one-unit increase in hopelessness among patients was associated with an increase in QOL, while as the hopelessness in caregivers increased, the QOL decreased. Compared to caregivers, a one-unit increase in the benefit of illness was associated with a substantial QOL improvement among patients (both ps < .05). The effects of role*family support and role*active coping strategies were marginally significant (ps = 0.08 and 0.09, respectively).
(Insert Fig. 2 here)
Among all confounding variables, better QOL was significantly associated with older age (p < .0001), having an income above $50,000 (p < .05), and experiencing less symptom distress (p < .0001). Furthermore, the role effect on QOL became non-significant, suggesting the effect of role was masked by the interaction effects between appraisals and roles. The appraisals (how they evaluate their circumstances) interacted with their roles in a way that hid the direct effect of the role on QOL. In simpler terms, how patients and caregivers appraised their situation could overshadow the direct influence that their specific role might have on their QOL.
In the final model, the coefficient of determination (R2) value was 0.7414, indicating approximately 74.14% of the variance in QOL was explained by the primary appraisals (appraisals of illness/caregiving, uncertainty, hopelessness, benefit of illness, role*hopelessness, and role*benefit of illness) and secondary appraisals (family support, dyadic illness-related communication, health behaviors, self-efficacy, active and avoidance coping strategies, role* family support, and role*active coping strategies) after controlling for the effects of the confounders (age, gender, income, and symptom distress) and role.