Statistical analysis
REGRESSION, SECONDARY
Participants’ demographic characteristics, as well as primary and
secondary outcomes at baseline are presented using frequencies, means
and standard deviations, or percentages. Further, absolute changes in
primary and secondary outcomes between baseline and 6 and 12 months
(within group) were calculated. As the study employed an open cohort,
the number of participants differs at baseline, 6 and 12 months (for
flowchart see figure 1).CONSORT 2010 flow diagram. *After enrollment, participants were
excluded prior to the analysis due to participants only completing
the demographic part of the questionnaire, moreover, some
participants withdrew after completion of the questionnaire and
were excluded from the study (N=34)To address the first research question, whether there was a
difference in the primary intervention outcome exhaustion and the
secondary intervention outcomes between the multifaceted and discrete
groups from baseline to 6 and 12 months, intervention effects for
primary and secondary outcomes were tested by means of linear mixed
modeling. Group and time variables were introduced as fixed factors in
the model, while a group×time interaction was an indicator of the
intervention effect. Baseline values of the primary and secondary
outcomes were controlled for in the model. The nested data structure
was accounted for by using a person-specific random intercept to model
the within-subject clustering over time. In addition, a model with a
school-specific random intercept to account for clustering within
schools was tested, however, it did not explain any additional
variance beyond person-specific clustering over time and was therefore
not used in further analysis.To answer the second research question, an adherence index was
added in the model as a covariate. In order to confirm that the
results were not influenced by the way adherence index was
constructed, we conducted an additional analysis with adherence index
as a categorical variable with three categories: low adherences
(values 0–2), moderate adherence (values 3–5), and high adherence
(values 6–8). The considerably smaller sample size for the second
research question is due to the fact that adherence indicators for
guideline recommendation 3 were preceded by the filter question,
resulting in a fewer number of participants responding to these
items.As schools are known for high levels of school personnel turnover –
during the trial, two schools in the multifaceted group and one in the
discrete group underwent organizational changes (entailing a change of
the principal and a transfer of the upper-level of education to
another school) – it was hypothesized that participants’ work
experience at the school and school organizational change could
account for differences in the primary and secondary outcomes. Work
experience at the school and organizational change were therefore
included in the model as fixed covariates. Separate models were fitted
for each of the outcomes.Estimates of intervention effects were reported as regression
coefficients with 95% confidence intervals (CI), with alpha
significant levels set to 0.05 for two-sided statistical tests. Data
were analyzed with the help of IBM SPSS Statistics 27, (IBM Corp,
Armonk, NY, USA).