3.4 Predictors of caregiver quality of life
As shown in Table 3, a three-step hierarchical linear regression model
was conducted to assess the ability of AD severity, illness perceptions
and caregiver SE to predict caregiver QoL. Only IPQ-R subscales that
significantly correlated with DFIQ scores were included in the model. No
demographic variables significantly correlated with QoL so were
excluded.
Model 1, which included AD severity as the sole predictor, explained
34.6% of the variance in caregiver QoL. Model 2 explained 71.4% of the
variance in caregiver QoL and included AD severity which accounted for
34.6% of the variance, and illness perceptions which accounted for
36.8%. Significant illness perception predictors were emotional
representations, consequences, and identity. Model 3 explained 72.2% of
variance of caregiver QoL. Adding caregiver SE to model 3 contributed
0.9% to the variance explained and did not result in a significant
difference. Additionally, caregiver SE was not a significant predictor.
The strongest predictors were consequences (β=0.62) emotional
representations (β=0.49), identity (β=0.31) and AD severity (β=0.29)
meaning that for every 1-unit increase in consequences, emotional
representations, identity and AD severity scores there were 0.62, 0.49,
0.31 and 0.29 increases in family impact scores respectively.
3.5 The
mediating role of caregiver self-efficacy between illness perceptions
and quality of life
To examine whether caregiver SE mediates the relationship between
illness perceptions and caregiver QoL, 7 separate models using different
illness perceptions as a predictor in each model were produced. For each
model, simple linear regressions were run for pathways a, b and c (see
supplement table d). Path a is the direct effect of the predictor
(illness perception) on the mediator (caregiver SE). Path b is
the direct effect of the mediator (caregiver SE) on the outcome
(caregiver QoL). Path c is the direct effect of the predictor
(illness perception) on the outcome (caregiver QoL). Path c’ is
the direct effect between the illness perception and caregiver QoL when
the mediator is taken into account. This pathway and the
indirect/mediating effect were produced in the PROCESS macro in SPSS.
Mediation analysis confirmed the direction of the regression paths and
found that caregiver SE had a statistically significant mediating effect
between all illness perceptions and QoL, except emotional
representations (see Table 4). The relationships between timeline
acute/chronic, illness coherence and identity and QoL were no longer
significant when the indirect effect via SE was accounted for,
indicating a full mediation effect. This implies that the effect of
these illness perceptions on QoL within those models was transmitted
entirely through SE. SE partially mediated between consequences,
personal control and treatment control and QoL. SE did not mediate
between emotional representations and QoL.