Nurture by Nature Feasibility Study

1. Background A newly published report from 2024 highlights significant socioeconomic, geographical, and seasonal disparities in 1-15 years-old Danish children's access to outdoor environments. While the overall time spent outdoors has remained stable since 2018 (averaging 2 hours and 41 minutes on weekdays and 3 hours and 24 minutes on weekends), the distribution of this time has changed. Most children spend their weekdays outdoor time in structured settings such as schoolyards and playgrounds, whereas weekend visits to natural areas have increased, particularly among families from higher socioeconomic status (SES) and in the summer months.

   The report reveals persistent socioeconomic and regional differences in how children engage with nature as also shown in other studies. Children in rural areas and smaller towns tend to spend more time outdoors overall, benefiting from the closer proximity to nature. In contrast, children in urban areas, particularly in the Capital Region and Region Zealand, use schoolyards, playgrounds, and urban parks, with fewer opportunities for spontaneous nature experiences. On weekends, however, urban families, particularly those from higher educational backgrounds, are more likely to travel to forests and beaches. Meanwhile, those parents with lower educational levels face greater barriers to nature access, including transportation limitations and fewer nearby green spaces. While their total outdoor time is comparable to other groups, they are significantly less likely to visit public natural areas, especially on weekdays.

   Seasonal differences further impact children's outdoor activity, with outdoor activities more prevalent in summer months and higher engagement with nature compared to winter. It is important to highlight a crucial distinction between general outdoor activities which includes playgrounds, yards and streets, and direct engagement with natural environments, emphasising that while children may spend considerable time outdoors, they do not necessarily interact with nature. The Danish Outdoor Council [Friluftsrådet] stresses the unique benefits of nature exposure, extending beyond conventional outdoor play at playgrounds. The outdoor environment can be categorized into two groups, the green outdoor environment which includes nature, and the grey outdoor environment which includes streets and other outdoor environments which are not nature.

   A recent Danish health report indicated that 5.2% of children with a mean age of 6.6 years assessed their overall well-being as low. Another Danish report among children aged 0-9 years stated that at least 16% of young children experience mental health issues or psychiatric diseases.

   Exposure to green outdoor environments might promote emotional well-being, reduce stress, fostering social connectedness, support cognitive development and better sleep quality among children, all of which are crucial for learning abilities and daily functioning. Furthermore, regular outdoor activities in nature have been shown to reduce ADHD symptoms, improve concentration, and enhance executive functioning. Additionally, it is speculated that nature-connectedness, e.g. the feeling of being emotionally and psychologically part of the natural world, fosters stronger social bonds and greater emotional regulation, all of which contribute to children's psychological well-being. However, the evidence for these benefits among young children is still limited as only few studies have been conducted among this age group.

   Findings from our previous qualitative study in rotating kindergartens (the same children were biweekly changing their kindergarten setting from rural more green outdoor to an urban with much indoor or grey outdoor time) showed that preschool children, while in nature in the rural setting, gained self-confidence by engaging in risky play (line climbing threes) and overcoming physical obstacles in the changing natural environment, opposite to the stationary environment presented by formal playgrounds in conventional kindergartens (urban setting). Further, the preschool teachers also stressed that those children that were more imaginative, engaged in fewer conflicts, were less interrupted during play, and used other motor skills while in nature as compared to when at the conventional playground. Similar results were found in a cluster randomized intervention study promoting more physical activity in the intervention kindergartens where significant improvement was seen in endurance performance. The investigators also showed previously that during the time the children spent in the outdoor kindergarten, they were more physically active as compared to when they were in the conventional kindergarten setting. In our stratified analysis of motor skills by level of maternal education, the investigators showed a tendency towards a lower risk of motor difficulties among children from outdoor- compared to children from conventional kindergartens, particularly for those children who had less educated mothers. This suggests that attending an outdoor kindergarten may improve motor abilities, in particularly among children from low SES families. However, other studies have shown better endurance performance only among children from high or medium SES families. These discrepant findings highlight the need for more studies especially targeted interventions.

   Given that up to 97% of preschool children attend kindergartens up to 40 hours per week, a nature-based intervention in kindergartens presents a practical, low-cost, and scalable solution to promoting child well-being by providing an optimal and equitable platform for fostering structured outdoor activities and nature engagement. By integrating nature-based interventions into early childhood education, municipalities can proactively support children's physical and mental health, while also addressing disparities in access to green spaces. Furthermore, recognizing that the need for outdoor activity is highest during winter, the intervention will be designed to operate year-round, ensuring that children remain active, engaged, and exposed to nature even during the colder months.

   Given the complexity of implementing structured nature-based interventions in kindergartens, conducting a feasibility study is a critical first step before progressing to a large-scale cluster randomized controlled trial (CRCT). Kindergartens vary in organizational structures, educational priorities, and staff capacity, all of which can impact the success of an intervention. A feasibility study will help assess recruitment potential among kindergartens, parental willingness to enroll children, and outcome response rates. Additionally, the feasibility study will identify logistical barriers, ensure ethical considerations are addressed, and inform necessary adjustments to enhance feasibility, compliance, and data quality before committing to a full-scale trial.

2. Aim and objectives The Nurture by Nature feasibility trial aims to assess the feasibility of conducting a future large-scale pragmatic cluster randomized controlled trial (CRCT) to evaluate the impact of a nature-based intervention on children's mental and physical health. The intervention will be implemented in kindergartens located in areas with a large proportion of social housing and compared with standard kindergarten activities in similar areas.

Specifically, the objectives of the present feasibility study are to investigate

1. completion rate in follow-up assessment of the Strengths and Difficulties Questionnaire (primary outcome),
2. recruitment rate and intervention fidelity (secondary outcomes),
3. completion rate in clinical exploratory outcomes (motor development, physical activity levels, sleep, and long-term stress of the children; sickness absence of both children and kindergarten personnel, and stress among kindergarten personnel and parents) and
4. safety of the intervention

Additionally, it will explore participants' (e.g. kindergarten personnel and parents) experiences and the acceptability of the intervention in a process evaluation.

The findings will inform the feasibility of the larger CRCT and contribute to the design and power calculations necessary for a future trial.

2.1. Hypothesis The investigators hypothesise that the Nurture by Nature feasibility trial is feasible (e.g. that the participants are willing to participate in the trial, complete assessments, and the intervention is accepted by the participants).

3. Study design 3.1. Trial design and framework The trial is a cluster randomised controlled trial (CRCT): a parallel group, cluster randomised controlled trial, where clusters are randomised to one of two study arms. After randomisation the participants in each cluster will stay in their assigned treatment arm during the entire trial. Primary endpoint will be inferred 17-18 weeks from baseline.

3.2. Clusters, Participants and setting The feasibility CRCT will be carried out in 5 kindergartens, as defined by the power calculation. The kindergarten management together with the staff responsible for the daily operations of the kindergarten will decide whether the kindergarten will participate in the CRCT in one of their kindergarten groups. Although the management team of the kindergarten decides whether or not to participate in the CRCT, it is up to the eligible participants (the kindergarten personnel, and the parents and children) if they give consent and contribute data to the trial.

Each kindergarten can contribute with one pre-existing group of children, which the investigators refer to as a cluster. Each cluster should include at least 11 eligible children consenting to participate.

The 5 clusters will be randomised; 3 will be allocated to receive the nature-based intervention, and 2 will be allocated to usual activities. Since the clusters are pre-existing groups within the kindergartens, they will include children not eligible, hence under the age of 4, and those who do not consent to contribute data or withdraw their consent. However, although some children in the clusters do not contribute data, all children in the cluster will receive the intervention if randomised to the intervention group.

Kindergarten personnel working in the included clusters, will be asked if they want to consent to contribute data, expectedly n=15.

Participants (children and parents or kindergarten personnel) who withdraw during the trial will not be replaced. Children who join the kindergarten group during the intervention period will not be enrolled in the trial nor contribute with data, but will receive the intervention if they are int the intervention group.

The overall number of participating children, parents and kindergarten personnel will be respectively n=56, n=56 and n=15.

From now on in the protocol, the term 'participant' will include children, parents and kindergarten personnel unless other is stated.

The trial will take place in the kindergartens and nearby nature settings.

4. Study investigation The intervention is a 14-week structured program during the winter months aimed at increasing nature-based activities to enhance well-being and health for children during kindergarten hours.

The usual activities clusters (the control comparator group) will follow usual practices which may include trips outside the kindergarten area as well as indoor and playground activities.

4.1. Adherence to the intervention Adherence to the Nurture by Nature intervention will be monitored and recorded during the trial. Adherence is defined as the number of outdoor sessions and activities done will be registered by kindergarten personnel.

5. Outcomes All outcomes will be measured at baseline and again at end-of-trial (after 14 weeks). In addition, physical activity and sleep will be measured at mid-trial. The three most important feasibility outcomes are categorised as primary or secondary, reflecting their significance and importance into the decision to progress to a larger cluster randomised trial.

The investigators will assess qualitative and quantitative outcomes in an exploratory manner.

5.1. Feasibility outcomes The feasibility outcomes will be assessed with the 'traffic light' system, where a set of progression criteria are categorized into red, amber, and green, each reflecting different levels of success (green = go, amber = modify, red = stop). The current nature-based intervention will be deemed feasible if most indicators are above the thresholds denoted in the 'green' column and no indicator below the threshold denoted in the 'red' column. The thresholds for red, amber, and green were decided by the project management group.

5.2. Qualitative outcomes and process evaluation To qualify the primary feasibility outcomes (quantitative assessments of recruitment and fidelity rates) the investigators will investigate the acceptability of the intervention among the kindergarten personnel and parents in a process evaluation which is in line with the Medical Research Council's recommendations for evaluating complex interventions, thus providing in-depth insight into experiences, challenges, and suggestions for improvement.

The main research objectives of the process evaluation are: To assess the fidelity of implementation (i.e., delivery of the intervention according to the trial protocol). To explore how kindergarten personnel and parents respond to and experience the intervention. To identify the key enablers and barriers to implementation.

The process evaluation will be based on qualitative interviews with up to 10 parents and up to 10 staff members and supplemented by quantitative measures of implementation fidelity. Fidelity will primarily be assessed as adherence to the intervention protocol. Implementation fidelity will be operationalized as the proportion of intervention weeks in which each intervention cluster delivers at least three planned nature-based activities or outings. This information will be collected through weekly structured checklists completed by kindergarten personnel, documenting frequency and duration of nature-based activities. Qualitative interviews will be used to explore contextual factors, participant engagement, and organizational conditions influencing fidelity, and to understand variations in implementation across clusters. Interviews with kindergarten personnel will explore how they implement the intervention, and how they experience the intervention in terms of meaning, workability, and compatibility with existing practices and roles. Implementation will be investigated in relation to a) the specific intervention activities (i.e., nature-based games) and b) the organizational structure (i.e., being outdoors in all weather in the winter season) that supports the delivery of the intervention. Interviews will be audiotaped and transcribed. The data material will be analyzed using implementation theory.

Results based on the process evaluation will tailor the nature-based intervention for a future full-scale CRCT in kindergartens.

6. Participant safety 6.1. Safety considerations

The intervention is generally considered safe, and the investigators do not anticipate an increased risk of adverse events or reactions in the study. Participants will be informed about the following potential risks associated with the intervention:

• emotional reaction to having hair cut for cortisol sampling Participants will be encouraged to communicate any discomfort or distress to the investigator immediately.

6. Trial procedures 6.2.1. Recruitment of kindergartens (clusters)

The recruitment of kindergartens will be done using three recruitment ways in denoted order:

1. Child and Youth Departments of municipalities with larger housing areas in Denmark and representatives of social housing areas will be contacted and informed about the project. This will be done by e-mail or phone. If the management accepts, the investigators will contact kindergartens in or near housing areas appointed by these municipalities, via email and phone. If interested, they will receive detailed project information by email and phone.
2. The investigators will contact the management in kindergartens directly by e-mail or phone with detailed project information.
3. The investigators will recruit kindergartens directly by social media, newsletters or advertisements in local papers. The management of the kindergartens will then be able to contact us if interested in more information about the trial.

6.2.2. Recruitment of children, parents and kindergarten personnel (participants) Upon acceptance by the kindergarten management, they will distribute project information to kindergarten personnel and parents by e-mail/communication platform like Aula, and place letters in the children's locker area, posters in the kindergarten. The written information will highlight the randomized nature of the trial that it is voluntary to participate, and that children, parents and kindergarten personnel not eligible or who do not consent to contribute data will still receive the intervention. Kindergarten management or personnel will further ask parents for permission to share contact information with the investigators. The investigators will then contact the parents and kindergarten personnel to arrange an individual oral information meeting by phone, online or on-site. The participants will be made aware of the possibility of bringing a support person (e.g., relative or friend) to the information meeting.

6.3. Individual oral information meeting The oral information meeting is planned individually , with the possibility of bringing a support person, by phone, online or on-site in the kindergarten The investigator delivering the oral information will be suitably qualified and experienced and will be authorised to do so by the principal investigator.

The oral information will include that:

• Participation in the trial is voluntary
• Participants have the right to minimum 24 hours reflection time before deciding to sign the informed consent or not
• Participants can at any time and without giving any reason, withdraw from the trial without affecting the potential participant's usual activity in the kindergarten

Further, the oral information will include: project aim, procedures, potential benefits and risks when participating in the trial, procedures for random findings during the project, procedures for securing the participants privacy and data protection, information on the trial organization, funding, as well as contact information on the primary investigator and other key investigators.

Children who participate in the trial will receive oral information and will be included in the conversations with the parents about the trial to the extent that the child in question can understand the trial situation. The child's own statements will-where relevant-be taken into account.

The investigator will make sure that participants have received and understood the information given to them.

To be enrolled in the trial inclusion criteria must be fulfilled, thus participants will be screened accordingly. Participants not eligible will not be asked to consider signing consent but will be informed that the children and kindergarten personnel are still part of the kindergarten cluster but will not give data.

Potential participants which fit the inclusion criteria wishing to consider participation further will be contacted by investigators after a few days (min. 24 hours). If they wish to participate in the study, a consent form will be sent to them by email or given directly to them in the kindergarten.

Participants who wish to sign the consent form right away, can do so and proceed to baseline assessments (questionnaires). Hair sampling, motor test and accelerometer assessment will be done later but before randomisation.

For each participant, the source documentation and eCRFs will document that informed consent was obtained before participation in the study. The signed informed consent form will remain in each participant's study file and will always be available.

6.4. Assessments and assessment timings Both assessment visits (baseline and end-of-trial assessments) will be conducted at the included kindergartens where the children feel safe.

6.4.1. Baseline assessment The baseline assessment visit will be carried out in the three-week period (termed 'week 0') before the randomization and the intervention begin.

At baseline the following procedures will be performed in the denoted order:

1. Assessment of child medical history and parental sociodemographic information entered in RedCAP
2. The parents fill in the outcome questionnaires in RedCAP
3. Activity tracker is given, and instructions for returning the devise are given
4. Scheduling plan with dates for the mid-trial (physical activity and sleep measure) and end-of-trial assessments
5. Sampling of child hair (investigator assessment)
6. Motor test (investigator assessment) The baseline hair sampling and motor test will be held in the kindergartens by trained investigators. Parents can be present, but it is not a demand.

Kindergarten personnel will fill out baseline questionnaire during kindergarten hours or at home via e-boks.

6.4.2. Mid-trial assessment The mid-trial assessment will be caried out in the two-week period (termed 'week 7').

At week seven of intervention the child will again wear the activity tracer to measure physical activity and sleep for four consecutive days. This will be given at the kindergarten by the investigators. The parents are welcome to be present, but it is not a must.

6.4.3. During the trial Text messages by mobile phone will be send weekly to the parents including a question related to child absence the last week.

Information on kindergartens personnel's sickness absence will be collected by the investigators from kindergarten personnel monthly.

Kindergarten personnel report daily activities performed related to the intervention (nature trips and activities carts used).

6.4.4. End-of-trial assessment The end-of-trial assessment visit will be carried out in the two-week period (termed 'week 15-16') after the intervention has ended and no later than 3 weeks after the last intervention week.

The end-of-trial assessment will be held in the kindergartens where the children will be present. It is optional for the parents to be present or to answer the questionnaire online. The investigators will ask the parents what they prefer. At end-of trial the following procedures will be done in the denoted order:

1. Information about the assessments

2. The parents fill in questionnaires

3. Questions about adverse events

4. Sampling of child hair (investigator assessment)

5. Motor test (investigator assessment)

6. Activity tracker is given, and instructions for returning the devise are given Kindergarten personnel will fill out end-of-trial questionnaire during kindergarten hours or at home via e-boks.

   Assessments performed outside these time limits will be registered as protocol deviations.

7. Biological material 7.1. Research biobank - hair samples for cortisol measurement Hair samples will be collected to measure cortisol levels, which serve as an indicator of chronic stress over time. Hair samples provide a reliable, non-invasive method to assess cortisol accumulation over several months, as hair grows approximately 1 cm per month, allowing a retrospective assessment of the stress levels. This will inform us whether the nature-base intervention affect chronic stress in the children.

8. Quality assurance and quality control The trial will be conducted in compliance with the study protocol. Detailed instructions and Standard Operating Procedures will be developed for specific tasks, as needed.

9. Statistical considerations 9.1. Determination of Sample Size and Progression Criteria The investigators have approached setting the sample size using Lewis et al.'s procedure to ensure adequate sample sizes for the feasibility study. This method means that should the true observed proportion be at or above the green threshold, then the sample is sufficiently large to be confident that the observed proportion will be at or below the red threshold in only 5% of tests. The sample size is set on the highest number; here, 56 children are divided into 33 in the intervention groups (3 groups) and 23 in the control groups (2 groups), for 90% power. No statistical testing is needed in this feasibility study. In this feasibility study, progression depends upon not having any indicator in the red zone and having all or nearly all green criteria achieved.

   9.2. General statistical approach As this is a feasibility study, the primary outcomes will be reported descriptively as proportions and percentages. The primary focus is on assessing the feasibility parameters (e.g., data completeness, recruitment, and fidelity), not hypothesis testing. Changes from baseline to end-of-trial in secondary and exploratory outcomes will be summarized descriptively and presented with 95% confidence intervals where applicable. Given the small sample size, these findings will be interpreted cautiously, as they are not intended to establish causal relationships. All statistical tests, if performed, will be two-sided and statistical significance will be claimed if the computed p-value is equal to or less than 0.05. However, all exploratory outcomes will be reported as preliminary and exploratory findings, intended to inform the design and analysis plan of future, more definitive trials.

   9.3. Trial conduct The Nurture by Nature intervention is non-invasive and non-medical with components focusing on nature, motor development, peer interactions, physical activity etc., that are commonly used in society and are not generally considered harmful. All participants will, however, be closely monitored for potential adverse reactions, but the investigators anticipate no ethical issues. The intervention is considered justifiable in a health research ethics perspective.

   The trial will be conducted in compliance with the protocol, and The Helsinki Declaration and meets the requirements of the regional ethics committees. The project will be carried out in full compliance with the General Data Protection Regulation (GDPR) and the Danish Data Protection Act, ensuring that all data protection requirements are strictly adhered to throughout the study period. The trial is registered in the Capital Region's research project register (Privacy), and data protection compliance has been reviewed and approved by Forskningsjura in accordance with the Danish Data Protection Act and the GDPR. Any substantial deviation from the protocol will only be implemented after review and approval from relevant regulatory authorities. Any deviation, however minor, will be documented and made available with the protocol.

10. Reimbursement In recognition of the lack of benefit for attending the assessment visits, the children will receive a gift card to Fætter BR of DKK 150, and the kindergarten personnel will receive a cinema gift card for two (valued around DKK 350), for completing the end-of-trial assessment visit. No compensation or transport reimbursement will be paid for attending any visits related to the Nurture by Nature intervention.

If the sponsor or the kindergarten management discontinues a participant from the trial, the children and the kindergarten personnel will receive the reimbursement. Whereas children who withdraws from the trial after baseline assessment but before the end-of-trial assessment will receive a reimbursement gift card to Fætter BR of DKK 75. Kindergarten personnel who withdraw from the trial before end-of-trial assessment will still receive the reimbursement.