As summarized in , the majority of participants were female, Caucasian, and well educated. Patients and FCs differed only in terms of gender, marital status, and pain. Compared to the patients, a greater proportion of the FCs was female and married or partnered and a smaller proportion had pain.
Baseline demographic and clinical characteristics of participants
Results of GMM analysis
Three distinct latent classes of anxiety symptom trajectories were identified using GMM (see ). The fit indices for the various models are shown in . As shown in , a three-class model was selected because its BIC was smaller than the two-class and four-class models, and by comparison of the other fit indices. In addition, each class in the three-class model had a reasonable size and interpretability (Jung and Wickrama, 2008
STAI-S trajectories for observed (actual) scores and estimated (predicted) scores for participants in each of the latent classes, as well as the mean STAI-S scores for the total sample.
Fit Indices for the State Anxiety Class Solutions
The parameter estimates for the three latent classes are listed in . The largest percentage of participants was classified into the Low Stable class (36.9%). These participants had total STAI-S scores that were low at baseline (mean 23.0), with a stable trajectory over the course of the study. Participants in the second largest class (i.e., Intermediate Decelerating class (32.5%)), had a mean baseline STAI-S score of 33.8 and symptom scores that decreased slightly over the course of the study. Participants in the third class (i.e, High class (30.6%)), had elevated STAI-S scores at baseline (mean 38.8) that increased and then very gradually decreased after the completion of RT.
Parameter Estimates for Latent Classes for State Anxiety from 7 Assessmentsa
Examination of possible patient/FC status effects and dyadic effects
No significant differences were found in patients’ and FCs’ baseline STAI-T or STAI-S scores. In addition, no significant differences were found in the proportions of patients and FCs among the three GMM classes described above (see ). Furthermore, even after taking patient and FC status and dependency within dyads into account in the 3-level GMM, no significant differences were found in the parameter estimates (intercepts and slopes) for the three GMM trajectories that were identified in the 2-level GMM. Given the absence of any dyadic or status effect, the relatively small proportion of dyads in the total sample, and the preference for model parsimony, the results of the 2-level GMM are reported in this paper.
Differences in Baseline Demographic and Clinical Characteristics among the Three Latent Classes
Differences in demographic and clinical characteristics among the three latent classes
No differences were found among the three latent classes in the proportion of patients and FCs (). However, differences in age, gender, ethnicity, marital status, having children living at home, presence of pain, and baseline KPS scores were found among the three latent classes.
Participants in the High class were significantly younger than participants in the Low Stable and Intermediate Decelerating anxiety classes. While women made up 53.8% of the total sample, post hoc contrasts revealed that a significantly higher proportion of women were in the High class (70.1%) compared to the Low Stable (41.9%) and Intermediate Decelerating (51.2%) classes. In terms of ethnicity, while 74.6% of the total sample was white, post hoc contrasts revealed that significantly higher proportions of nonwhites were in the Intermediate Decelerating (30.5%) and High (35.1%) classes compared to the Low Stable class. In terms of marital status, a higher proportion of those in the High class (40.8%) were not married compared to those in the Low Stable class (22.6%). In addition, a significantly higher proportion (24.2%) of participants in the High class had children at home, compared to those in the Low Stable class (8.0%).
In terms of physical functioning, post-hoc contrasts demonstrated that individuals in the Intermediate Decelerating and High classes had lower KPS scores at baseline than those in the Low Stable class. In addition, the presence of pain was different among the three anxiety classes, with post hoc contrasts revealing that a greater proportion of those in the High class (66.2%) reported pain, compared to those in the Low Stable (37.6%) and Intermediate Decelerating (42.7%) classes.
Differences in baseline trait anxiety among the three latent classes
Significant differences in baseline STAI-T scores were found among the three latent classes. Participants in the High class reported the highest trait anxiety scores followed by those in the Intermediate Decelerating class, whose scores were significantly higher than those reported by the Low Stable class (all p < 0.002, ).
Differences in baseline CES-D scores among the three latent classes
As shown in , significant differences were found among the three latent classes in baseline CES-D scores, with the High class reporting the worst depression scores, followed by the Intermediate Decelerating class, followed by the Low Stable class (all p < .001).
Differences in the trajectories of CES-D scores among the three latent classes
Differences in the trajectories of CES-D total scores are illustrated in . Post hoc contrasts for the class by time interactions for changes over time in the CES-D score are summarized in the legend for .
Figure 2 Changes over time in Center for Epidemiologic Studies – Depression total scores for participants in each of the three latent anxiety classes. Post hoc contrasts for intercept 1 < 2 < 3a; and slopes 1a and 2b ≠ 3. (ap<0.0001, (more ...)