Participant numbers

Figure 1 shows the trial profile. The number of pupils in each class/school year was larger than we had anticipated and, therefore, having recruited 60 schools, the number of pupils included was greater than the required 1500. Of the 2242 potentially eligible students in the 60 participating schools, 10 left the school prior to randomisation and baseline data collection and the parents or carers of 11 pupils did not consent to their child’s participation in any aspect of the study. All other children (n = 2221; 1064 in the schools that were randomised to intervention and 1157 in the control schools), irrespective of whether or not they had all measurements recorded, were included in the trial and used as denominators for baseline comparisons between the two randomised groups.

FIGURE 1

Trial profile. N refers to number of schools; n is the number of participants (school pupils). None of the schools withdrew from the study and so all of the randomised units are present at baseline and follow-up. The percentage given in brackets for the (more...)

These numbers include a small number of participants (n = 65) whose parent/caregiver refused consent for one or more measurements (most commonly weight and occasionally waist). Up to two catch-up visits were made to schools to obtain data on any pupils who were absent on the day of data collection for their school, but inevitably some pupils will have been absent on the day of both the main and catch-up visits to their school at either baseline or follow-up. No child refused assent to complete the questionnaires, but in a small number of cases it was not possible to code the dietary data because we could not read what was written or identify a food from a brand name. A small number of pupils did not assent to waist or weight measurements, and the proportion of pupils with valid accelerometer data was influenced by the requirement that they had 3 days, each with at least 8 hours of valid wear time.³³ In total, at both baseline and follow-up, between 82% and 96% of participants had data on diet outcomes, BMI and WC, and approximately 60% had valid accelerometer data (see Figure 1). With the exception of valid accelerometer data the number of children included in the main analyses (1825 to 2121) was greater than the 1275 that our sample size calculations showed were required for the main analyses. For accelerometer-based measurements, data were available for 1252 children for the main analyses, 23 (0.02%) fewer than the estimated requirement.³³ Proportions with valid data for each measure were similar at both baseline and follow-up, and in intervention and control schools (see Figure 1).

Baseline characteristics

Baseline characteristics, including for accelerometer return and wear time, were similar in intervention and control schools with the exception of reported screen viewing time on Saturdays, which was 15 minutes greater per day in participants from the control schools than in the intervention schools (Table 3).

TABLE 3

Comparison of baseline characteristics by randomised group

Main intention-to-treat analyses

In the main ITT analysis with adjustment for baseline variables, none of the three primary outcomes differed between children in schools allocated to the AFLY5 intervention and those allocated to control schools (Table 4). The intervention was effective on three out of nine of the secondary outcomes after taking account of multiple testing in these analyses: pupils’ self-reported time spent on screen viewing at the weekend (Saturday) and self-reported consumption of snacks and of high-energy drinks were lower in intervention schools than in control schools (see Table 4). There was no strong evidence that the intervention affected the other secondary outcomes in these analyses, especially after taking into account multiple testing.

TABLE 4

Main ITT analyses of the effect of the AFLY5 intervention on primary and secondary outcomes assessed immediately after the end of the intervention (numbers of participants vary by outcome as indicated in the table)

Per-protocol analyses

Table 5 shows the results of the per-protocol analyses for primary and secondary outcomes. In these analyses children from 16 classes in 12 out of the 30 intervention schools were excluded because their teacher had delivered fewer than 70% of the lessons. The results of the per-protocol analyses were broadly consistent with the ITT analyses results, with no evidence of effect on the three primary outcomes or most of the secondary outcomes. As with the ITT analyses, there was evidence of beneficial effect on self-reported screen viewing on Saturdays and consumption of high-energy drinks. The point estimate for the reduction in self-reported consumption of snacks was similar to that seen in the ITT analysis but the strength of evidence was marginal, particularly after multiple testing was taken into account.

TABLE 5

Per-protocol analyses of the effect of the AFLY5 intervention on primary and secondary outcomes assessed immediately after the end of the intervention. Numbers vary by outcome as indicated in the table

Sensitivity analyses

The sensitivity analyses that we undertook to explore assumptions about missing data produced results that were consistent with the main analyses (Tables 6–9). When we looked separately at time spent in MVPA and time spent in sedentary behaviour by weekday and weekend, the results were consistent with each other and with the main results (both values for the difference between the two estimates p > 0.2; Table 10).

TABLE 6

Sensitivity analysis 1: ITT analyses of the effect of AFLY5 intervention on primary and secondary outcomes assessed immediately after the end of the intervention including participants who have complete data on each outcome at baseline and follow-up

TABLE 9

Sensitivity analysis 4: ITT analyses of the effect of the AFLY5 intervention on primary and secondary outcomes assessed immediately after the end of the intervention, with missing data for either baseline or follow-up measure of an outcome assumed to (more...)

TABLE 10

Main ITT analyses of the effect of AFLY5 intervention on accelerometer-assessed outcomes separately for week and weekend days (n = 1252)

TABLE 7

Sensitivity analysis 2: ITT analyses of the effect of AFLY5 intervention on primary and secondary outcomes assessed immediately after the end of the intervention only including participants with complete data at baseline and follow-up on all three primary (more...)

TABLE 8

Sensitivity analysis 3: ITT analyses of the effect of the AFLY5 intervention on primary and secondary outcomes assessed immediately after the end of the intervention, with missing data for either baseline or follow-up measure of an outcome assumed to (more...)

Analyses stratified by sex and school area level of deprivation

Table 11 shows the results presented separately for girls and boys. The effect estimates for the accelerometer-measured primary outcomes looked different in girls and boys, with the effect of the intervention on time spent in MVPA being very close to the null in girls but decreased (opposite to the effect expected) in boys and on time spent in sedentary behaviour decreased in girls but increased in boys (again the opposite of what we expected). However, as noted in the section Testing differences of effect by sex and by area deprivation, these stratified analyses are exploratory and we did not design the study with an aim (or sufficient numbers of participants) to be able to detect sex differences. Furthermore, there was no strong statistical evidence that these effects did differ by sex (both p_interaction = 0.4). For all other outcomes, with the exception of consumption of snacks, the effects were broadly similar in girls and boys. The intervention appeared to have a stronger effect on reducing the consumption of snacks in girls than in boys, with statistical evidence that this difference was unlikely to be caused by chance (p_interaction = 0.006).

TABLE 11

Main ITT analyses of the effect of the AFLY5 intervention on primary and secondary outcomes assessed immediately after the end of the intervention in girls and boys. Numbers vary by outcome as indicated in the table

Table 12 shows the results according to school area level of deprivation (divided into thirds). For some outcomes, point estimates did seem to suggest that the intervention had different effects within thirds of school area deprivation, but there was no consistency across the thirds for differences in most outcomes (that is no monotonic difference with each category increase in deprivation) and no statistical support for differences by the IMD.³⁴ The two possible exceptions were time spent in sedentary behaviour assessed by accelerometer and self-reported screen viewing on weekdays. For time spent in sedentary behaviour assessed by accelerometer the intervention appeared to result in greater time spent in sedentary behaviour (opposite to what was expected) in pupils from schools in the middle deprivation third, with some statistical support for this being different from that seen in the lowest third, but the effect was similar in the two extremes (lowest and highest thirds of deprivation). For self-reported screen viewing on weekdays there did appear to be a monotonic increase in effect (reduced time spent screen viewing) as deprivation category increased, but there was no statistical support for differences between categories and this pattern was not seen for reported screen viewing at weekends.

TABLE 12

Main ITT analyses of the effect of the AFLY5 intervention on primary and secondary outcomes assessed immediately after the end of the intervention stratified by thirds of the IMD (numbers vary by outcome as indicated in the table)

Mediation effects on outcomes

Following the intervention, there was evidence that 3 of the 10 potential mediators (fruit and vegetable self-efficacy, maternal limitation of sedentary behaviour and knowledge) were higher in the intervention group than in the control group (Table 14).

TABLE 14

Main ITT analyses of the effect of the AFLY5 intervention on potential mediators assessed immediately after the end of the intervention (numbers vary by mediator as indicated in the table)

Table 15 shows the main effect of the intervention on the three secondary outcomes found to be affected by the intervention, both before and after adjustment for potential mediators. Adjustment for maternal limitation of sedentary behaviour and child knowledge attenuated the effect of the intervention on time spent screen viewing at the weekend by 22%. There was no notable change in the effect of the intervention on consumption of snacks or high-energy drinks following adjustment for mediators.

TABLE 15

The main effect of the intervention on the three secondary outcomes found to be affected by the intervention, both before and after adjustment for potential mediators

Primary analyses

Table 18 shows a breakdown of the resource use and costs incurred during the training days and the delivery of the AFLY5 lessons from the combined school and provider perspective. The main cost drivers for the intervention were the claims by the schools for replacement teachers needed to cover the teachers’ attendance at the training days (£5.00 per pupil, £5095.00 in total); the trainers’ fees (£2.00 per pupil, £2166.00 in total); the time spent by the research staff organising and attending the training days (£2.00 per pupil, £2492.00 in total); and the printing costs of the materials for the AFLY5 lessons and the homework (£6.00 per pupil, £6694.00 in total). We estimated the opportunity cost of implementing AFLY5 in schools (i.e. the cost of teaching AFLY5 minus the cost of teaching the usual curriculum based on data from schools in the control arm) to be £0.05 per pupil. The costs varied by school, ranging from approximately £13.00 to £36.00 per pupil. The variations between the schools were driven by the costs of the teachers’ attendance at the training days.

TABLE 18

Active for Life Year 5 resource use and costs: providers and school perspectives

The cost–consequence analysis showed that, for the three secondary outcomes that were affected by the intervention, it cost £18 per child (£18,944 in total) to reduce self-reported time spent on screen viewing at the weekend by 20.86 minutes, self-reported consumption of snacks by 0.22 snacks per day and self-reported consumption of high-energy drinks by 0.26 servings per day.

From the teachers’ perspective, teachers spent, on average, more time travelling to the training day venue than they usually spent travelling to school; this equated to an additional 0.68 minutes’ travel time per pupil, generating an extra cost of £0.19 per child (£206 in total).

Sensitivity analyses

Table 19 shows the results of sensitivity analyses for the primary (perspective of combined provider and school). These results suggest that the main analyses are robust to our assumptions regarding missing data.

TABLE 19

Sensitivity analyses for the cost–consequence results from the provider and school perspective

Secondary analyses

Only 626 (28%) parental questionnaires [278 (13%) in the intervention and 348 (16%) in the control arm] were returned. In the returned questionnaires the item non-response varied between 0% and 6%. Table 20 shows the results of the cost differences between the intervention and control arms from the perspective of the parents and the NHS, using a CCA and including maximum numbers for each item. After adjustment for the child’s age, sex, area deprivation level for the school and the engagement of the school in health-promoting activities (over and above AFLY5), all of the parental and NHS costs appeared greater in those from schools randomised to intervention compared with those randomised to control. However, all of these results were imprecisely estimated with wide CIs consistent with no difference. With the exception of the NHS costs, adjustment for covariables produced notable differences in comparison with the unadjusted results (although results were all consistent with the null hypothesis, whether or not adjusted). The IMD³⁴ is the covariable that has most effect, and it contributed to change in all of the results that differed with adjustment. Other covariables that contributed to some of the change in results with adjustment were age (total cost from a parental perspective), child’s sex (costs of parental time) and the level of school involvement in healthy activities (expenditure in out-of-school activities). The greater NHS cost is likely to be exaggerated as it was influenced by one participant who was reported to have had surgery for a condition that is unlikely to have been influenced by the intervention (adrenal surgery); this was despite the question that specifically asked about treatments that were related to physical activity injury. Other variables in the cost–consequence analyses were largely normally distributed with no evidence of effect by ‘outliers’.

TABLE 20

Difference in mean costs from the perspective of parents and the NHS (numbers differ for each item)