Inferential statistics addressing Research Question 1 – pre- and post- post-intervention comparisons

The first step in using inferential statistics concerned Research Question 1: ‘Were there observable improvements in caregiver outcomes immediately after the third intervention session in participants who took part in the intervention versus controls?’ Improvements would be indicated by reductions in depression, burden and reaction to stressor scores, and by increases in self-efficacy scores.

To compare the pre- and post-intervention scores of the intervention and control participants, Mann-Whitney tests were carried out for each outcome variable using SPSS. This non-parametric test was selected as a conservative approach to analysing the data, due to the non-normal distributions of scores. Table 5.3 details the pre- and post-intervention means for post-intervention participants and control participants. At this stage in the analysis, individual and group participants were grouped together as ‘intervention participants’, to gain a direct comparison with the control group.

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Table 5.3 Pre- and post-intervention mean scores for intervention vs. control participants, and results of Mann-Whitney comparisons of change scores (*

denotes p<0.05)

RMBPC: Revised Memory and Behavior Problems Checklist; CESS: Caregiver External Stress Scale; CESD: Centre for Epidemiologic Studies – Depression; SE-OR:

Self-Efficacy for Obtaining Respite; SE-DB: Self-Efficacy for Responding to

Disruptive Patient Behaviors; SE-CT: Self-Efficacy for Controlling Upsetting Thoughts about Caregiving; ZBI: Zarit Burden Interview.

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The results displayed in Table 5.3 show that when a direct comparison is made between intervention and control participants, significant differences are found for two of the outcome measures: RMBPC-reaction (caregiver reaction to behavioural stressors;

U=86.00, p=.015) and ZBI (caregiver burden; U=93.50, p=.016). These results mean that from pre- to post-intervention, participants receiving the intervention showed significantly reduced reaction to caregiving stressors, and significantly reduced burden, when compared to control participants. These results support the hypothesis underlying the first research question; the intervention led to improve outcomes as predicted for two of the outcome measures. No significant benefits were observed for the other outcome measures (depression and self-efficacy scores).

To examine these results more closely, the category ‘intervention participants’ was then broken down further into ‘individual participants’ and ‘group participants’, and further Mann-Whitney tests were carried out, to explore whether the individual or group delivery of the intervention had any bearing on the results. Table 5.4 below gives the mean pre- and post-intervention scores for individual, group and control participants, and Table 5.5 displays the results of Mann-Whitney tests making these further comparisons.

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Table 5.4 Pre- and post-intervention mean scores for individual, group and control participants (standard deviations are reported in brackets)

Individual (N=10) Group (N=18) Control (N=13) RMBPC-number (pre) RMBPC: Revised Memory and Behavior Problems Checklist; CESS: Caregiver External Stress Scale; CESD: Centre for Epidemiologic Studies – Depression; SE-OR:

Self-Efficacy for Obtaining Respite; SE-DB: Self-Efficacy for Responding to

Disruptive Patient Behaviors; SE-CT: Self-Efficacy for Controlling Upsetting Thoughts about Caregiving; ZBI: Zarit Burden Interview.

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Table 5.5 Results of Mann-Whitney tests comparing individual vs. control and group vs. control participants (* denotes p < 0.025; significance level corrected for multiple comparisons)

Ind. vs.

Control

Group vs.

Control

M-W U p M-W U p

RMBPC-no. 45.5 .232 97.0 .441

RMBPC-reac. 36.0 .123 50.0 .013*

CESS-no. 36.5 .762 87.0 .906

CESS-reac. 38.0 .897 89.5 .981

CESD 34.5 .057 83.5 .183

SE-OR 49.5 .705 73.5 .256

SE-DB 50.0 .539 101.5 .787

SE-CT 50.5 .539 73.0 .146

ZBI 36.0 .077 57.5 .025*

RMBPC: Revised Memory and Behavior Problems Checklist; CESS: Caregiver External Stress Scale; CESD: Centre for Epidemiologic Studies – Depression; SE-OR:

Self-Efficacy for Obtaining Respite; SE-DB: Self-Efficacy for Responding to

Disruptive Patient Behaviors; SE-CT: Self-Efficacy for Controlling Upsetting Thoughts about Caregiving; ZBI: Zarit Burden Interview.

Table 5.5 shows that when comparing the Individual participant group with the Control group, using the change in outcome scores from pre- to post-test, no significant

differences were found. Comparing the Group and Control conditions using the change in scores from pre- to post-test, Table 5.5 shows significant differences on the RMBPC-Reaction (stress in response to behavioural issues) scores. Participants who received the group intervention experienced significant improvements in caregiver reaction to problematic behaviours of the person with dementia, as compared to the control group.

This result is consistent with the hypothesis that the intervention would be associated with positive caregiver outcomes (in this case, a reduction in subjective evaluation of

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the stressfulness of difficult behaviours) as compared to a control condition. Looking at the result for caregiver burden (ZBI) between the group and control participants

(U=57.5, p=.025), this result is borderline non-significant when adjustment for multiple comparisons is taken into account.

To gain a clearer view of what was happening for each of the three participant groups over the course of the intervention (for example, whether the intervention did not benefit individual participants at all, or whether the above results could be related to the small number of individual participants), within-group comparisons were made. Within-group changes can also show whether an intervention has had a positive effect on participants, or whether intervention participants have remained stable while control participants experienced a decline (Elvish, Lever, Johnstone, Cawley & Keady, 2013).

The Wilcoxon signed-rank test in SPSS was selected here, due to non-normal

distribution of the outcome measure scores. The Wilcoxon test is usually considered to be a non-parametric test similar to a t-test, and was used in this case to explore within-group differences between pre- and post-test scores.

Table 5.6 below demonstrates the results of conducting the Wilcoxon test for each group of participants. In this case, the test was one-tailed, as the direction of change in the outcome measures could be predicted by a hypothesis: it was hypothesised that participants receiving the intervention would show improvements in outcomes

(decreases in depression, burden and subjective stress scores; increases in self-efficacy scores).

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Table 5.6 – Wilcoxon test results for individual, group and control participants (showing Z score with p values in brackets; significant values at the p < 0.05 level are denoted by *)

Individual (N=10) Group (N=18) Control (N=13) RMPBC-number -.983 (.163) -1.071 (.142) -.675 (.250) RMBPC-reaction -.766 (.222) -1.967 (.025*) -1.837 (.033*) CESS-number -.412 (.340) -.225 (.411) .000 (.500) CESS-reaction -.135 (.446) -.171 (.432) -.511 (.305)

CESD -.949 (.172) -1.685 (.046*) -.046 (.482)

SE-OR -.296 (.384) -.245 (.403) -1.120 (.132)

SE-DB -1.604 (.055) -1.744 (.041*) -2.143 (.016*)

SE-CT -.866 (.193) -2.137 (.017*) -.561 (.288)

ZBI -.970 (.166) -1.348 (.089) -1.939 (.026*)

RMBPC: Revised Memory and Behavior Problems Checklist; CESS: Caregiver External Stress Scale; CESD: Centre for Epidemiologic Studies – Depression; SE-OR:

Self-Efficacy for Obtaining Respite; SE-DB: Self-Efficacy for Responding to

Disruptive Patient Behaviors; SE-CT: Self-Efficacy for Controlling Upsetting Thoughts about Caregiving; ZBI: Zarit Burden Interview.

The results of the Wilcoxon tests show no significant differences between pre- and post-test scores on any of the measures for participants in the Individual condition. For participants in the Group condition, significant differences were observed at the p<0.05 level for the measures RMBPC – Reaction (subjective experience of stress relating to memory and behavioural problems of the person with dementia), CESD (depression), SE-DB efficacy relating to coping with difficult behaviours) and SE-CT (self-efficacy for controlling difficult thoughts about caregiving). For Control participants, significant differences were observed in the measures RMBPC – Reaction, SE-DB, and ZBI (caregiver burden).

It is, of course, necessary to describe the direction of these differences in scores for each of the groups; for most of the outcome measures used in this study (for example,

measures of depression and burden), a reduction is a desirable outcome, while for the

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self-efficacy measures, an increase would be desirable. Looking at the significant change in ZBI scores in the Control group, for example, and comparing it to the pre- and post-test scores shown earlier in Table 5.4, this change actually represented an increase in caregiver burden across time, which is a negative outcome.

The directions of change between pre- and post-test scores for the three participant conditions on each of the outcome measures are illustrated in Figures 5.2-5.6.

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Figure 5.2 Change in RMBPC-Number and RMBPC-Reaction for each of the three conditions. (* denotes significant pre- to post-intervention change).

Figure 5.2 illustrates the direction of change for each of the three conditions (Individual, Group and Control) on the two components of the RMPBC scale – number of

behavioural and memory problems exhibited by the person with dementia, and caregiver reaction (or subjective stress) in response to these. The graphs show that for the

Individual and Group Conditions, the number of behavioural symptoms, and the experience of associated stress, reduced between pre- and post-test, with the opposite trend being observed in the Control participants. In the second of the two graphs, the drop in caregiver stress appears to have a steeper gradient for the Group participants than for the Individual participants; this represented a significant within-group change for Group but not Individual participants.

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Figure 5.3 Change in CESS-Number and CESS-Reaction for each of the three conditions.

Figure 5.3 shows the direction of change for each of the three groups as measured by the two components of the CESS scale – number of external stressors and subjective experience of stress due to external factors. Each of the three groups appeared to

experience a slight increase in externally-related stress over time, despite the number of external stressors remaining stable (Control participants) or showing a slight increase (Individual participants) or slight decrease (Group participants). As external sources of stress were being measured in the study but not targeted by the intervention, we would not expect to see any change in the experience of external stress attributable to the presence or absence of the intervention.

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Figure 5.4 Change in CESD for each of the three conditions. (* denotes significant pre- to post-intervention change).

Figure 5.4 compares the three participant groups across time in terms of the CESD scale, measuring depression. While the Control participants showed a small average increase in depression score between the pre- and post-test periods, both the Individual and Group participants showed a reduction in depression score. This direction of change is consistent with the hypothesis that the intervention would relate to a reduction in caregiver depression, and this reduction was significant for Group participants.

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Figure 5.5 Changes in SE-OR, SE-DB and SE-CT for each of the three conditions.

(* denotes significant pre- to post-intervention change).

Figure 5.5 illustrates the direction of change for each of the self-efficacy sub-scales (self-efficacy for obtaining respite, dealing with difficult behaviours and controlling difficult thoughts about caregiving) from pre- to post-test. For SE-OR and SE-DB, each of the three participant groups showed an increase over time, while for SE-CT, the Control group showed a small decrease over time while the Individual and Group participants showed an increase. As the intervention aimed to build self-efficacy, the observed patterns for the Individual and Group participants are as hypothesised;

however, the fact that improvements were also observed in SE-OR and SE-DB in the Control group was not as predicted.

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Figure 5.6 Changes in ZBI for each of the three conditions. (* denotes significant pre- to post-intervention change).

Figure 5.6 shows the direction of change for each of the three participant groups in terms of the ZBI (caregiver burden) scores. The Control participants had a significant increase in burden score over time, while the Individual and Group participants showed a non-significant reduction. This direction of change is consistent with the hypothesis that the intervention would have significant benefits for burden when compared to a control group; in this case, the intervention may have acted as a protective factor against the increases in burden experienced by Control participants.

In several of the figures above (particularly those showing depression, burden and reaction to behavioural stressor scores), the Individual and Group participants clearly showed similar trends between pre- and post-intervention, with these trends being in the opposite direction to the Control participants’ scores. It is possible that the lack of significant benefits to Individual participants may reflect low participant numbers and

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lack of statistical power to detect changes. Lack of statistical power has been raised as an issue in studies with comparable sample sizes (such as Gaugler et al, 2011).

5.3.4 Inferential statistics addressing Research Question 2 – three-month follow-up