Interactive electronic devices (IEDs) have become a common part of young children's lives, yet research on this topic remains limited. Most studies utilise cross-sectional designs and present inconsistent evidence regarding the benefits and harms of IED use. Some findings suggest that IEDs may negatively impact sleep quality, be linked to visual impairment, and lead to reduced and more negative interactions between parents and children. However, it might also have a positive effect in helping language learning in young children when IEDs are co-viewed with parents and improving literacy, mathematics and science skills.

Due to this conflicting evidence, health guidelines for young children do not provide specific recommendations on using these devices, leading policymakers to request more information in this area. In conversation with parents and nursery practitioners, they told us they were confused about the benefits and hams of using these devices and wanted further guidance.

The primary aim of this study is to investigate the long-term association between IED use (duration and mode) and development outcomes in 3-to-5-year-old children. The researchers will also explore the longitudinal association between IED use (duration) and other outcomes, including BMI z-score, movement behaviour, motor skills, parent-child interaction and school readiness.

Children and their parents or caregivers from both low, mid and high-income areas in England will be invited to take part. Children can participate if they are between 3 and 4 years old when they join the study, have received consent from their parent or caregiver, and have provided verbal agreement to participate. However, children will not be eligible if their parents or caregivers do not speak or understand English or if the child has been diagnosed with a developmental disorder by a medical professional before the baseline or follow-up measurements.

Data collection will occur at the start of the study and one year later when children are 4 to 5 years old. Parents will be asked to download an app called EARS on the smartphone and/or tablet that the child uses. The app will measure how long they use the device (IED duration) and the specific apps accessed during device usage (IED mode).

Child development will be assessed through the following measures: 1) working memory, including visual-spatial and phonological aspects; 2) ability to control, referred to as inhibition; 3) the ability to control and redirect attention, defined as shifting; 4) self-regulation; 5) social development; 6) numeracy skills; and 7) expressive vocabulary. Child development will be measured using the Early Years Toolbox app and recorded on an iPad.

The researchers will also measure a set of secondary outcomes, including 1) BMI z-score; 2) 24-hour movement behaviour (i.e. physical activity, sedentary behaviour and sleep); 3) motor development (i.e., gross motor skills and fine motor skills); 4) parent-child interaction; 5) school readiness.

The researchers will also measure other things that might influence IED use or emerging abilities, such as participants' demographics (i.e., sex, age, ethnicity and caregiver education), parenting styles, parents' smartphone addiction, the presence of screen viewing policy at the early year's settings.

To thank the early years settings for participating, each will receive £100 for every data collection session. Parents will receive a £30 high street e-voucher for each data collection session in which they participate. There are no risks of physical injury or harm involved in this study. All researchers entering the nursery will have been subject to an enhanced Disclosure and Barring Service (DBS) check and are permitted to engage in controlled activity. If the research team observes a significant developmental delay in the child while conducting the health and development measures, they will notify the nursery staff, who will then communicate this information to the parents. Parents may feel uncomfortable downloading the app (EARS) onto their electronic devices to track how long the device is being used and the type of apps in use. The app has been designed for research purposes and approved by Sheffield Hallam University Digital Technology Services. Participants will download the app through the official Apple or Google Stores, which offers additional security and convenience. Participants will be advised to delete the app after each data collection point.

The investigators will have regular group meetings throughout the project with parents, carers, nursery teachers and policymakers to gather ideas and opinions and share our findings. These discussions will help researchers improve the project.

The findings will help inform public health guidance on children's device usage. The researchers will share the knowledge gained from this study with all participants, write policy briefs and scientific papers, and present the findings at conferences.

Quality assurance Researchers undertaking the measurements are highly experienced in the procedures and analysis. The investigators are utilising only validated tools that are well-established in the literature. The exposure and use of interactive electronic devices (e.g., tablets and smartphones) will be measured by an app that will access information directly from the participant's devices (Android or iOS) using mobile sensing software to capture screen time and app usage (Lind et al. 2023). The app has been successfully used to measure smartphone use in children (Bagot et al., 2022; Wade et al., 2021).

The measurement of emerging abilities, our primary outcome measure, has been validated and widely used in the literature (Howard et al. 2017). The investigators will use an administration fidelity checklist to assess practice across researchers before the start of data collection. A range of secondary outcomes will be recorded (i.e. BMI (calibrated scales and repeated measures), movement behaviour (accelerometry Cliff et al. 2024), motor development (NIH toolbox, Reuben et al., 2013), parent and child interaction (StimQ2, Cates et al. 2023). These measurements have been used in the SUNRISE study, which is collecting data on children at this age in 63 countries around the world (https://sunrise-study.com/) and published in a protocol (Okely et al., 2021).

Training videos and support have been provided by the SUNRISE team and have been used to inform our study protocol. Since child development is influenced by a number of covariates, the investigators have selected the most commonly reported in the literature and suggested by our PPI group (i.e. sex, age, ethnicity, maternal education, parenting style (PSDQ- SV. Robinson et al. 2001), attendance to childcare, parental addiction to smartphones (SAS-SV, Kwon et al., 2013) and screen viewing policy.

Data processing Data capture forms have been created for applicable measures to standardise data input and aid with data entry. In terms of data processing and analysis. The investigators will conduct preliminary data cleaning, exploring whether values of continuous variables are within range, plausibility of means and standard deviations, and validity of coded categories. The investigators will assess data distributions and identify any univariate outliers from graphical methods and from cases with very large, standardised scores disconnected from other scores and multivariate outliers by graphical methods and inspection of leverage/Mahalanobis distances, discrepancy and influence statistics. Any possible errors will be investigated on an individual basis. The investigators will also investigate the extent, pattern and nature of missing data. If the proportion of missing data is small (below 5%), they will consider complete case analyses. If the amount or pattern of missing data precludes complete case analysis, the investigators will consider data imputation. Multiple imputations will be used due to their robustness to the type of data missingness. If imputation is conducted, sensitivity studies will be conducted by comparing results derived from data with and without imputation.

Data analysis Descriptive analysis The sample will be summarised descriptively. The investigators will report the number of children in each educational unit and primary and secondary outcomes by time point (baseline and follow-up). For continuous outcomes, summary information will be presented as means (standard deviations (SD); ranges). For categorical outcomes, summary information will be presented as frequencies (percentages). The need for variable transformations to stabilise variance or achieve Normality will be assessed.

Inferential analysis The following test variables will be considered for the analysis: 1) IED duration; 2a) IED mode educational; 2b) IED mode age-appropriate.

1. Multilevel regression modelling of primary outcome The investigators conceptualised a 2-level random intercepts multilevel model, with children clustered within educational units. This model will consider EA at the follow-up to be the outcome measure designed to answer the primary research questions: How is IED duration (hours per day) and mode (educational vs. non-educational; age-appropriate vs. non-age-appropriate) at baseline, controlling for child-level covariates (including EA baseline scores) and educational unit-level covariates, associated with EA at follow-up in a multilevel model in which children are clustered within educational units? The variance partition coefficient (VPC; the proportion of residual variance associated with each level of the model) will be assessed via a null model before proceeding to a covariate model. The investigators will consider merging the levels in the model if VPC statistics reveal negligible clustering effects (negligible residual variance at the level of the educational unit). A non-linear multiple regression modelling will be conducted if there is evidence for a non-linear relationship between the level of IED usage at baseline and EA at follow-up, allowing for a single maximum (corresponding to optimum levels of baseline IED usage) or plateau; otherwise, linear regression models will be conducted. If data indicates an optimum IED level of usage associated with a specific maximum value of EA score at follow-up, alternative non-linear functional forms will be considered with maxima or plateauing features, including polynomial (e.g. quadratic) and logarithmic forms, and piecewise functions. The investigators will compare the fit of multiple distributions in the vicinity of any turning point and select the best-fitting model in this region to maximise the accuracy with which the maximum value of EA may be obtained. Confidence intervals will be fitted around the function to derive a range of values for the maximum value.

   The investigators will conduct both non-fully adjusted and adjusted models, with adjusted models adjusted for all covariates at each level of the model. Non-adjusted models will include (i) the single determinant of the level of IED usage (duration) at baseline, (ii) the determinants of IED predominant mode at baseline (as defined above), and (iii) determinants of IED duration and mode. These determinants will all be added in at the child level of the model. First-order interactions will be included within unadjusted models to capture any differential effects in assessing levels of IED usage with differing predominant modes of use. Any interaction revealed to be of substantive importance will be retained in a re-cast model alongside all main effects. Adjusted models will be based on the included variables of both IED duration and IED predominant mode, any interactions of substantive importance and all controlling covariates at the appropriate level of the model. The investigators will not use automated modelling strategies for variable selection and will retain all main effects in the adjusted model. However, collinearity will be assessed in adjusted models and consider deletion of controlling covariates if excessive collinearity is apparent (variance inflation factor >=5 for any variable).

2. Multilevel regression modelling of secondary outcomes The investigators will conduct multiple linear regression modelling on all numerical secondary outcomes and multiple logistic regression modelling for the binary secondary outcome measure, using the same model structure as for the main analysis of the primary outcome. If any evidence is revealed for non-linearity between the level of IED duration and the secondary outcomes, The investigators will consider non-linear modelling for the analysis of the primary outcome; else, they will consider linear modelling. In both cases, the same set of covariates and interactions defined for the primary outcome will be adjusted. No adjustment for multiple analyses will be made; hover, all analyses will be planned a priori and reported in full.

3. Multilevel regression modelling: subsidiary analysis To explore the socio-ecological correlates of IED duration at the individual (gender, age and ethnicity), interpersonal (maternal education, parenting style and smartphone addiction), and organisational (childcare policy and attendance) levels, will be conducted as a subsidiary analysis, considering the above set of variables as determinants of IED using the variables that are reported as controlling variables.

   Random intercepts and multiple linear regression modelling on the outcome of IED duration will be conducted at baseline. A 2-level hierarchical structure will be used, with variables designated as Individual or Interpersonal attached at the lower (child) level and variables designated as Organisational attached at the upper (educational unit) level.

   Any relationships revealed during this process will be used in future modelling to generate hypotheses within a wider structural equation modelling framework.

4. Sensitivity analysis and data reporting For the primary outcome, the plan is to conduct sensitivity analyses to assess the sensitivity of the model to certain assumptions, as mentioned above. The investigators will compare parameter estimates of tested variables in unadjusted and adjusted models. For the multilevel modelling of the relationship between IED duration and EA, both random slopes and random intercepts models will be used to assess variation in slopes between higher-level units. If data imputation is viable, models will be run with and without imputed data (see 'Data cleaning and assessment of missing data').

For linear and non-linear regression models of continuous numerical outcomes, in the main and subsidiary analyses, the investigators will report all unstandardised parameter estimates with associated 95% confidence intervals and p-values. For logistic regression models, all odds ratios with associated 95% confidence intervals and p-values will be reported. If evidence is revealed for a non-linear trend, the investigators will report the functional form of the best-fitting curve and identify the location of any maximum or commencement of plateauing effects. All regression modelling assumptions will be checked, including homogeneity of variance and normality of outcome variables for each value of an independent variable, using residual analysis. Statistical analyses will be conducted using MLwiN version 3.06 (Charlton et al., 2022) and Stata version 17 (Stata Corp 2021).

Inclusion Criteria:

• Children between 36 and 48 months old at the time of enrolment, who have received parent/carer consent for participation and provided verbal assent

Exclusion Criteria:

• Parents or child do not speak and/or understand English.
• Child who is clinically diagnosed with a developmental disorder by a medical professional prior to either baseline or follow-up assessments.

Participants will be recruited from diverse areas in the Midlands and the North of England. We will utilise two recruitment approaches: 1) through early years settings and 2) directly, using social media, flyers, and engagement with general practitioners (GPs).

Data will be shared via a repository, and requests can be made directly to the Sheffield Hallam Research Data Archive (SHURDA), email address: library-research-support@shu.ac.uk.

If data is requested during the project period, a data-sharing agreement will be issued between Sheffield Hallam University and the data requester. In this case, data sharing will be restricted to ensure it does not impact the research team's publication plan.

At the outset of analysing the follow-up data in July 2027, the linkage key that connects identifiers to personally identifiable information will be destroyed, ensuring the data is fully anonymised. No additional modifications to the data formatting will be made.

The fully anonymised data will be stored in SHURDA and be retained for 10 years from the last time a third party requested access.

We plan to deposit the data at the Sheffield Hallam Research Data Archive (SHURDA) in September 2027. The data will be securely archived in SHURDA for 10 years, starting from the last time a third party requests access. After this period, all data will be deleted from the Research Store.

Fully anonymised data will also be deposited in an open-access repository (SHRUDA) under a CC-BY license as guided by the research funder NIHR. Requests can be made directly to SHRUDA (library-research-support@shu.ac.uk).

When depositing the data, no further changes to the formatting will be necessary, as all required actions will be carried out as the research progresses. All data will be stored in CSV (comma-separated values) format. CSV files are compatible with many software applications, allowing potential users to easily store and reuse the data.

The Data Management and Access Plan submitted to the funders (NIHR) can be accessed through the URL below. Please note that the data management described in this link pertains to all three work packages of the project: WP1 - Systematic Review, WP2 - Longitudinal Study, and WP3 - Qualitative Study. However, the registration provided here specifically refers only to WP2 - Longitudinal Studies.