Study design and setting
The current study is a cluster randomized trial with two conditions (intervention and control) with preschools as clusters and the unit of randomization. A cluster randomization design was chosen because the intervention targets policy on the organizational level in preschools and preschools are natural clusters. Units of observations are preschool children and preschool teachers. The report of this trial protocol is guided by SPIRIT reporting guidelines (31) and we provide the detailed SPIRIT checklist (see Additional file 1). We will report the findings of the trial according to guidelines outlined in the CONSORT extension for cluster randomized trials (32). The current study is being conducted in the Stockholm region of Sweden. To date in the Stockholm region, there are 3,0969 children (1-5 years old) enrolled in a total of 539 public preschools (personal communication with Stockholm region representative, 2020-06-15). The Stockholm region can be divided geographically and administratively into 13 districts which vary in size, number of preschools, children and resources.
Ethical approvals and informed consent
has been obtained from the Swedish Ethical Review Authority (Dnr. 2020-03002) and this study has also been pre-registered at a database for clinical studies (https://clinicaltrials.gov) with reference number: NCT04569578. All items from the World health Organization Trial Registration Data Set can be found clinicaltrials.gov. The registration of the study was completed before the recruitment of participants. An information document, describing the study purpose and procedures, will be provided to every participant and further information is provided on the project website (https://ces.sll.se/var-Thverksamhet/aktiviteter-och-projekt/rorelseprojektet/). Written informed consent will be obtained from parents of the participating children and participating preschool teachers before enrollment in the study. (See Additional file 2 for the consent form in English) Please refer to Additional file 3 for the details about how the informed consent will be collected.
The required sample size to obtain a statistical power of 0.90 was projected with a change in MVPA as the main outcome variable and by using the means and standard deviations of the aforementioned observational preschool study assessing PA (27). A 5 minute change in MVPA has been suggested in previous meta-analysis to be a resoable target a of clinical importance (33). Assuming an effect size of 5 min MVPA, an an intra-preschool correlation of 0.2, a standard deviation of 25, coefficient of variation of 0.3 (average preschool size of 35 children 3-5 years), approximaley 2800 children (from 85 preschools) should be retained.
Study population and recruitment
Based on other similar studies and the previously mentioned preschool study conducted by our research group (27), approximately 30% total non-participation is expected. Specifically, we expect an estimated accelerometer non-compliance rate of 10% (i.e. participants with insufficient wear-time) and a drop-out rate of 20% throughout the study period. Consequently, we aim to recruit approximately 4000 children aged 3-5 years from 100 public preschools within all 13 districts in the Stockholm region.
Figure 1 illustrates the recruitment of preschools and subsequent recruitment of preschool children and teachers based on the inclusion/exclusion criteria. Due to the logistical burden and time limit of the study, only preschools with more than 60 enlisted children are eligible for participation. In order to ensure a representative sample in each district, approximately 30% of all public schools with more than 60 enlisted children (all age groups) in each district will be randomly asked to participate in the study. The random selection of preschools for study invitation will be fulfilled by contacting preschool principals following a random order of invitation generated by Stata (Additional file 4. programming codes, random_invatation_preschool) until the number of preschools agreed to participate reached the approximately 30% of all public preschools in that district. The recruitment of preschool children and teachers will be initiated provided that preschool principals agree to participate. All 3-5 years old children enlisted at the participating preschools will be invited to participate and the participation will be confirmed by the informed consent of parents. In addition, full-time teachers at the participating preschools will also invited to participate and provide informed consent. Preschools with less than 10 children with parental informed consent and children who are not able to able to take part in PA measures (e.g. mobility disability) will be excluded from participation. The limit of at least 10 children with parental informed consent per preschool was chosen due to logistical reasons to accommodate the accelerometer measurement burden in the study.
A total of 156 preschools were asked to participate in the study and 127 preschools (with median of 11 preschools per district) agreed to participate. Apart from 3 preschools that collected less than 3 parental informed consents, 124 preschools participated in the baseline data collection. No preschools were lost to follow up.
Randomization and blinding
Preschools will be stratified by the 13 Region Stockholm districts because geographical, organizational and resource factors in each district are likely to differ and influence the implementation and effectiveness of the policy. After baseline assessment, preschools will be randomly assigned to the intervention or control condition by 1:1 ratio within each of the 13 districts to ensure equal representation of intervention and control preschools. Block randomization with districts as blocks is conducted with randomizr package in R (Version3.6.1) (Additional file 5. programming codes: randomization_preschool). A single-blinded approach will be adopted where outcome assessors will be blinded to the treatment allocation.
The intervention components were developed based on the aforementioned observational preschool study (27) and systematic review data on the effectiveness of PA interventions for preschoolers, i.e. (i) organizational changes at the policy level, (ii) unstructured outdoor play, and (iii) instructions to preschool personnel on how to encourage child PA behaviors (21). The intervention framework, a study website and delivery of information, has been established on the directional management level within all 13 districts within the Stockholm region and will be delivered directly to each intervention preschool after baseline measures and the randomization process. To increase parental engagement in the intervention group, participating parents will be provided with an information package (multi-lingual multi-media content) describing the intervention components, their importance, and practical information on how to engage in active transportation to/from preschool.
The intervention framework (on preschool level) includes:
- Formalized PA policies:
- A minimum of 3 hours of total daily outdoor time, to be scheduled both in the morning and in the afternoon.
- At least 10 minutes of teacher-led active play per day. An activity bank will be provided for inspirations of possible teacher-led activities.
- A minimum of 1 weekly outdoor excursion which is commonly realized as a visit to local parks, playgrounds or other recreational facilities. A map of recommendations of potential outdoor excursion areas will be provided.
- Meet the children outdoors when they arrive at preschool and/or picked up by their parents.
- Only use screen-based devices for educational teaching purposes.
- Communicating to, and encouraging, the parents to actively transport their children to and from the preschool.
- A study website will provide information on the study process and measurements. The activity bank for inspiration of teacher-led active play and a map of recommendations for outdoor exertion, mentioned in PA policy b and c above, will also be accessible through the website. This study website may also serve as a platform for interprofessional education where preschool teachers can share and communicate about engagement in activities and their experience.
- Weekly follow-up and feedback by web-based questionnaires to determine fidelity and dose of intervention.
Intervention development and theory base
The interest for the intervention began when the previously mentioned observational study, found a positive association between having a formalized PA policy in preschools and children’s PA levels (27), which attracted attention from politicians and stakeholders in the City of Stockholm. Realizing the potential of policy to increase PA among preschool children, the stakeholders took a formal political decision that all public preschools in the Stockholm region should implement a formalized PA policy. This decision is documented in the public preschools’ financial steering plan and implies that all public preschools in the Stockholm region should exert effort and financial resources in the implementation of a PA policy. In addition, a policy package should be developed and evaluated to provide a “model” for preschools to understand what PA policies to implement and effective strategies for implementation. The intervention policy package has been developed in co-creation among the research group, municipal childcare stakeholders, district officers from the 13 Stockholm region districts and a reference group consisting of preschool principals and teachers. The policy package has been discussed and acknowledged among all co-creators to increase the engagement, buy-in, feasibility, relevance and sustainability of the intervention policy package as recommended by a previous meta-analysis on the effectiveness in co-creation of research (34). The Behaviour Change wheel (35) was chosen as a theory base to understand and reflect on essential conditions (capacity, opportunity and motivation) for behaviour change in relation to the intervention's functions and policy category. (The detailed logical model of theory of change for the policy package intervention based on behavioral change wheel can be found in Additional file 6 theory of change).
Implementation of the intervention
This intervention is expected to scale up upon proof of effectiveness and feasibility. Therefore, no special implementation facilitation will be provided - to ensure external validity. Specifically, to ensure complete scalability we will utilize a pragmatic approach where minimal additional resources are provided (no support beyond that of the intervention package), thereby evaluating whether the routine resources disposable to Swedish preschools are sufficient for the implementation of the intervention. The implementation of the policy package will be examined in detail following the process evaluation framework by Moore et al (36). To which extent the policy package is implemented (dose and fidelity) is followed up weekly by web-based questionnaires. More details of process evaluation are illustrated in the process outcomes section.
Preschools randomized to the control condition are not provided with the intervention package and are encouraged to keep their usual practice and routines during the intervention period. However, in this pragmatic trial, control preschools are also under the influence of financial steering document and they are free to implement any PA policy. In addition, communication between teachers from intervention and control groups and the study website may contribute to contamination. Therefore, PA policies in control preschools will be monitored at baseline, mid-point (3 months) and endpoint (6 months) to capture possible contamination effects and understand the possible change in their PA policy throughout the intervention.
Outcomes and measures
In the present study, several instruments are used to assess outcomes in children and teachers. An additional file provides an illustration of all the instruments used, corresponding to the measured outcome variable, time point of measurement and group relevance (i.e measurement in both intervention and control groups or intervention group only) in detail (See Additional file 7). Questionnaires will be distributed via email to each respondent through Webropool 3.0. All questionnaires used can be found in Supplementary material 3 questionnaires. Questionnaires answered by preschool personnel are distributed only in Swedish. The questionnaires distributed to parents are available in Swedish, English, Arabic, Turkish, Somali, Tigrinya and Swahili to cater to the need of parents with language barriers as an effort to retain a study sample containing individuals from different countries of origins. The questinnaires included as additional files (see Additional file 8-15) are only available in english and questionnairs in other languages can be made available upon reasonable request. How the data will be managed after collection and plan for result dissemination can be found in Additional file 3.
Physical activity levels (primary outcome) and sedentary time (secondary outcome) in children
PA levels in children such as total PA, MVPA, light PA (LPA), ST and steps will be measured objectively using triaxial GT3X+ accelerometers, which have been tested extensively for reliability and validity in both pediatric and adult populations (37). Children will be instructed to wear the accelerometer, on the non-dominant wrist, for 24 hours during 7 consecutive days except during water activities (e.g. when showering and swimming) at both baseline and 6 months follow-up. The non-dominant hand will be predetermined by parents (information collected together with informed consent). Set-up and analysis of accelerometer data will follow validated age-specific criteria and recommendations (37). The accelerometer data sampling frequency is 30 Hz and data will be analyzed at 1-s epochs which suits the sporadic movement pattern of preschool children (37). Raw accelerometer data will be downloaded through Actilife and analyzed using the GGIR package (38). The classification of PA intensities and ST will follow the cut-offs developed for children with wrist-worn Actigraph GT3X+ by Hildebrand et al (39, 40). Steps will be determined using the Verisense step algorithm, which is integrated in GGIR to determine steps for wrist-worn accelerometry (41). Accelerometer data consisting of ≥ 10 hours/day wear time with > 3 days of measurement days will be considered valid (42). However, participants with less valid days will be included in sensitivity analysis.
Results will be reported in categories of PA during the preschool time, PA outside preschool time and PA during the entire day. This is to explore how the preschool policy affects PA during the preschool time frame and to assess potential extended effect beyond the preschool time frame and compensatory behavior (43). Change in MVPA will be emphasized since PA in higher intensity is suggested to have greater benefits for health outcomes (3).
Musculoskeletal fitness in children (secondary outcome)
Musculoskeletal fitness, in terms of handgrip strength, will be measured by an analogue dynamometer (TKK 5825, Grip-A, Takei, Tokyo, Japan) validated in preschool-aged children (44). Measurement of handgrip strength will be conducted at baseline and at 6 months follow-up by trained field workers to the nearest 0.1 kg on both dominant and non-dominant hands.
Psychosocial functioning of children (secondary outcome)
The psychosocial functioning of children will be assessed by a parental report of the Strength and Difficulty Questionnaire (SDQ) which has been used extensively worldwide and validated also in Swedish settings (45). Parents will be asked to fill in the SDQ and sleep questionnaire at both baseline and 6 months follow-up. The SDQ questionnaire uses a 3-point Likert scale to measure the children’s psychosocial strength and problems summarized into an emotional symptoms scale, conduct problems scale, hyperactivity scale, peer problem scale and prosocial scale. All scales except for the prosocial scale are then summarized into a total difficulties score. The result for psychosocial functioning will be reported as the total difficulties score as well as separate scores on each of the scales mentioned above.
Sleep of children (secondary outcome)
Sleep will be measured using a combination of 24h accelerometry, a sleep time diary during periods of accelerometer measurements and a parental questionnaire to reflect sleep quality during the past 6 months. All measurements for sleep will be conducted at baseline and 6 months follow-up. Sleep onset, sleep duration and waking up will be determined by algorithms integrated in GGIR (46). Appropriate algorithms for detection of sleep in children will be used. The sleep time diary included in the parental measurement week questionnaire consists of two questions regarding children’s wake up time and bedtime. In addition, parents will answer questions in SDQ and sleep questionnaire about children’s sleep duration and quality during the past 6 months and these questions are adapted from the validated Ages and Stages Questionnaire (47). To minimize the burden of answering different questionnaires, the sleep quality questions were added to the SDQ questionnaire; therefore, the questionnaire is named SDQ and sleep questionnaire.
Screen time in children (secondary outcome)
Children’s screen time, in minutes of screen time per day, will be reported by parents at baseline and end-point during periods of accelerometer measurements in the parental measurement week questionnaire.
Sick leave of children (secondary outcome)
Sick leave frequency and duration from 12 months prior to the intervention baseline and during the 6-months intervention period (18 months in total) will be collected from the the City of Stockholm central preschool absence database. A database to which all parents of preschool children in Stockholm report all sick leave.
Adiposity of children (secondary outcome)
Weight, height and waist circumference will be measured, by trained field workers, at baseline and 6 months follow-up. All measurements will be conducted twice and each measurement result will be recorded to the nearest 0.1 of the respective unit. Weight will be measured by validated scales (calibrated scale: VB2-200-EC, Vetek AB, Väddö, Sweden) and height will be measured by stadiometers (portable stadiometer: Seca 213, Seca, Chino, CA, USA). Weight and height will then be used to calculate body mass index (kg/m2) and children will be classified as normal weight, overweight or obese based on body mass index criteria developed by Cole et al (48). Waist circumference will be measured at the level of the navel directly on the skin (49). Due to the COVID-19 pandemic field researchers are required to conduct the measurements outdoors; thus, the waist circumference measurement may be conducted over thin clothing in cold weather.
Demographic information, children and parents (descriptive)
Information on the age and sex of parents of the participating children will be derived from the personal registry number provided upon the consent of participation. Parents will also, at baseline, be asked to complete a descriptive information questionnaire including questions regarding their education level, occupation, country of birth, height and weight.
Children’s PA opportunities outside preschool time (process outcome)
Children’s PA opportunities including participation in organized sports and active transport to/from preschool will be assessed via parental measurement week questionnaire (during the weeks of accelerometer measures at baseline and 6 months follow-up). Parents will be asked about the time, duration and type of organized sports, and mode of transportation to/from preschool. In addition, parents will also answer an active transport questionnaire at baseline and 6 months follow-up regarding children’s general frequency of active transport, mode of transport, parental perception of the distance and condition of transportation route during the past 6 months. Moreover, several parental practices (outdoor time during the weekend, parental perception of PA, parental PA levels, and active play with parents) which could potentially influence children’s daily PA levels will also be assessed by questions included in the parental questionnaire.
Parental evaluation of the project and interview (process outcome)
A parental evaluation questionnaire will be distributed to parents of all participating children at 6 months follow-up. This evaluation questionnaire includes the parental rating (5 score scale) and open-ended questions on information quality, communication and perception study influence and experiences of study participation. Parents have the opportunity to report any unintended adverse effects of the intervention in this instrument. These questions will be used in qualitative analysis of potential facilitators and barriers of the study. At the end of this questionnaire, parents will be asked whether they want to participate in an interview to further explore the experience, influence and potential of the study.
Physical activity levels, sedentary time and sleep in preschool teachers (secondary outcome)
Similar to children’s PA levels, ST and sleep, these variables in teachers will also be measured objectively using triaxial GT3X+ accelerometers (37). Preschool teachers will wear the accelerometer, on the non-dominant wrist, for 24 hours during 7 consecutive days at baseline and 6 months follow-up. Minutes in total PA, MVPA, LPA, ST and total steps during the preschool time, outside preschool time and during the whole day will be reported for teachers. Sleep in preschool teachers will also be analyzed using 24 h accelerometry. Set-up and analysis of accelerometer data will be performed following validated age-specific criteria and recommendations (37).
Musculoskeletal fitness of preschool teachers (secondary outcome)
The method to assess musculoskeletal fitness in children will be used also for preschool teachers. Musculoskeletal fitness in terms of handgrip strength will be measured by an analogue dynamometer (TKK 5825, Grip-A, Takei, Tokyo, Japan). Measurement of handgrip strength will be conducted at baseline and at 6 months follow-up by trained field workers and recorded to the nearest 0.1 kg on both dominant and non-dominant hands.
Sick leave of preschool teachers (secondary outcome)
Sick leave frequency and duration from 12 months prior to the intervention baseline and during the 6-months intervention period (18 months in total) will be collected from the City of Stockholm central preschool absence database.
Adiposity of preschool teachers (secondary outcome)
Weight and height will be measured by validated scales (calibrated scale: VB2-200-EC, Vetek AB, Väddö, Sweden) and stadiometers (portable stadiometer: Seca 213, Seca, Chino, CA, USA) and waist circumference will be measured at the level of the navel directly on the skin (49). Due to the COVID-19 pandemic field researchers are required to conduct the measurements outdoors; thus, the waist circumference measurement may be conducted over thin clothing in cold weather.
Demography of preschool teachers (descriptive)
The age and sex of the preschool teachers will be derived from their personal registry number provided upon consent to participate in the study.
Preschool policy and environmental characteristics (process outcome)
Preschool environmental/organizational characteristics such as available play equipment, playground characteristics, current policies and working practices will be assessed by the validated Environment and Policy Evaluation and Observation as a Self-Report Instrument (EPAO-SR) (50). The preschool playground characteristics and size will be double-checked and measured objectively via spatial mapping using publicly available satellite imagery (e.g. Google maps). Preschool level routine screen time will be reported by preschool teachers in intervention preschools weekly through the intervention weekly follow-up questionnaire and via the validated EPAO-SR (50). The use of EPAO-SR is important to identify what policies/practices that are in place prior to the intervention, and to assess if any other preschool environmental/organizational changes take place during the intervention period. It is also a crucial tool to measure the extent of any contamination by the intervention to the control preschools.
Implementation of the policy package (process outcome)
Fidelity and dose of the implemented policy package will be documented through a weekly follow-up questionnaire, answered by preschool staff, throughout the intervention period. The extent to which the intervention can be normalized into preschool staff’s regular practice will be assessed through the validated (51) No-MAD questionnaire (an instrument for assessing implementation work based on normalization process theory) (52) at 6 months follow-up.
Preschool teachers’ evaluation of the project (process outcome)
Communication, acceptance, facilitators and barriers for implementation will be assessed through teachers’ evaluation questionnaires provided by all participating preschool teachers. At the end of the teachers’ evaluation questionnaire, preschool teachers will be asked whether they are willing to participate in focus groups and interviews. Focus groups and interviews with preschool personnel will also be undertaken post-intervention to collect more in-depth perspectives regarding the adequacy of the intervention, the feasibility of implementation and suggestions for improvements. These qualitative discussions will generate rich data regarding the logistical challenges and the strengths and weaknesses of the intervention that could be missed in questionnaires. An experienced moderator, using a semi-structured interview guide, will facilitate the discussions. Sample questions will include:
What challenges did you experience when implementing the intervention?
What solutions did you undertake to deal with these challenges?
What characteristics of the intervention do you feel were most appropriate for increasing PA participation among preschoolers?
Focus groups and interviews will be audio-recorded and transcribed verbatim.
The baseline demographic characteristics of the participants will be summarized descriptively. Drop out participants’ characteristics will be explored by comparison to the non-drop-outs. Fidelity and dose of implementation will be summarized as a score (fidelity x number of weeks of compliance). The change in PA levels and secondary outcomes, from pre- to post-intervention, will be analyzed with linear mixed-effect models (to allow both fixed and random effects) nested on preschool level. The linear mixed-effects model can test several aspects of the study effects, e.g. effects over time inside a group, and groups against each other at a given time (e.g. intervention vs. control at 6-months follow-up). Subgroup analyses will be conducted to analyze the effect of the intervention in relation to socioeconomic aspects. Furthermore, we aim to explore if the COVID-19 pandemic has modified any implementation aspects of the intervention (via questionnaires on how various routines including outdoor time, hygiene aspects at preschools, homestay and transportation mode to/from preschool have changed following the COVID-19 pandemic).
Timeplan of the project
Figure 2 illustrates the schedule of enrollment, interventions, and assessments according to SPIRIT guidence.