Strategies to Prevent Type 2 Diabetes Mellitus among School Children: A Systematic Review

Introduction: The prevalence and socioeconomic burden of type 2 diabetes mellitus (T2DM) and associated co-morbidities are rising worldwide among school children thereby raising a public health concern. Aim: The aim of the review was to explore global literature concerning the various strategies utilised in prevention of type 2 diabetes mellitus among school children and their efficacy. Methodology: A retrospective search of articles published from 2009 to 2019 was done. The following electronic databases; Cochrane, Embase, ERIC, Google Scholar, MEDLINE, PEDRO, PubMed and Science Direct were individually searched using specifically developed search strategies. Methodological quality was evaluated using the Critical Appraisal Skills Programme (CASP) tool and by two independent reviewers. Results: Eleven studies of sound quality were included. The studies show that primary prevention of type 2 diabetes among school children is cardinal as children will grow up knowing about the disease and its consequences. The prevention of type 2 diabetes mellitus requires various combinations of interventional program elements including dietary education/counselling, physical activity, diabetes knowledge, competence building, school, social and community support being considered concurrently. None of the studies identified was done in Africa. Conclusion: Findings concretise that healthy diets and exercise outcomes coupled with explicit programs are key to type 2 diabetes mellitus prevention among school children. www.scholink.org/ojs/index.php/rhs Research in Health Science Vol. 5, No. 2, 2020 65 Published by SCHOLINK INC.


Introduction
Type 2 diabetes mellitus (T2DM) is one of the fastest growing and largest global health burdens with high levels of morbidity and mortality (Wichit et al., 2016). Due to its chronic nature, which demands lifelong maintenance, T2DM is also a tremendous economic burden on the individual, family and the entire health care system (Meetoo, 2014;Wang et al., 2009). The combined global prevalence of diabetes and prediabetes among youths has increased from 9% to 23% (May et al., 2012) with a rising in overall prevalence diagnosed cases in the past decade (Yeow et al., 2019). Prediabetes prevalence is related to weight and is present amongst 12% with normal weight, 18% who are overweight and 30% in obese adolescents (Vangeepuram et al., 2015). If prediabetes incidence remains constant, the proportion of youth with type 2 diabetes is projected to increase by 49% by 2050 globally with the mean age at diagnosis of type 2 diabetes being 12-14 years and initial diagnosis being as young as 5 years (Imperatore et al., 2012). According to Smart et al. (2018), the changing disease rates are almost certainly attributed to changes in several dietary factors such as changes in the quality, quantity and source of food, over-consumption of cheap fatty and energy dense foods as well as changes in lifestyle.
A reduction in physical activity and an increase in sedentary lifestyles including spending long hours playing games on the computer, iPads and tablets, play station and watching TV has also contributed significantly to the increase in prevalence rates (Temneanu et al., 2016;Gulati et al., 2014;WHO, 2014).
Diabetes has classically been defined as a group of metabolic diseases characterized by hyperglycemia which is increased concentration of blood glucose due to disturbances in glucose metabolism as a result of: (i) peripheral insulin resistance in muscle and adipose tissue; (ii) excessive hepatic glucose production (iii) impaired insulin secretion from the pancreas, (iv) or a combination of all three (ADA, 2019; Yeow et al., 2019;Meetoo, 2014;Polikandrioti & Dokoutsidou, 2009). Symptoms of marked hyperglycemia include polyuria, polydipsia, weight loss, sometimes with polyphagia, and blurred vision, impairment of growth and susceptibility to certain infections may also accompany chronic hyperglycemia especially in children (ADA, 2019). The American Diabetes Association (ADA, 2019;2018), indicated that type 2 diabetes is diagnosed based on a fasting plasma glucose (FPG ≥126 mg/DL [7 mmol/L]) or the two hour plasma glucose value following a 75 g oral glucose tolerance test (>200 mg/DL [11.0 mmol/L]) or having an HbA1c of 6.5%. Glycosylated haemoglobin (HbA1c) to which glucose is bound, is tested to determine average blood glucose levels over the past two to three months (ADA, 2018;IDF, 2017;, as this is widely regarded as an accurate measurement for diabetes assessment. Type 2 diabetes mellitus, once considered a rare condition among the young population, now accounts for about 15% to 45% of all newly diagnosed cases of diabetes in children and teenagers drastically surpassing type 1 diabetes in some regions (Cara, 2019). www.scholink.org/ojs/index.php/rhs Research in Health Science Vol. 5, No. 2, 2020 66 Published by SCHOLINK INC.
Children in whom T2DM develops are at risk of complications from the disease, including retinopathy, neuropathy, cardiovascular, renal disease and early mortality (Foster et al., 2010). The longer individuals have these conditions, the greater the risk of complications, resulting in discomfort, ill health and absenteeism from school, they also suffer psychosocial consequences including; social alienation, low self-esteem, discrimination and decreased mental acuity such as lower grade point averages, standardized test scores and perceived academic performance (Totura et al., 2015;Contento et al., 2010). Type 2 diabetes mellitus also imposes a substantial burden on the economy worldwide in the form of increased medical costs (ADA, 2013). The US national health expenditure to treat T2DM and its complications is estimated to be around US$210 billion among adults and US$14 billion among children per year and this has drastically increased in recent years (Totura et al., 2015). The direct costs of T2DM consume from 2.5% to 15.0% of annual healthcare budgets depending on available treatments and local prevalence worldwide. Hence interventions aimed at preventing childhood T2DM and the associated risks are increasingly important at primary level (Totura et al., 2015;Wang et al., 2009).
Schools offer an ideal setting for lifestyle interventions because the obesogenic lifestyle behaviours are less well developed in children and are therefore amenable to change (Pansier & Schulz, 2015).
Schools present opportunities for reducing the risk of diabetes since no other institution has as much contact time with children, moreover, schools can implement environmental changes that affect available foods, physical activity/education, class curricula, policies and the acceptability of healthy behaviours (Chinnici et al., 2019;Manios et al., 2018;Hall et al., 2014;Muzaffar et al., 2014;DeBar et al., 2011;Singhal et al., 2011;Foster et al., 2010). Furthermore, schools are uniquely positioned to promote healthful interventions that can provide an unparalleled opportunity to reach many children including the ones with the highest risk of developing type 2 diabetes (Chinnici et al., 2019;Manios et al., 2018;Hall et al., 2014;Muzaffar et al., 2014;DeBar et al., 2011). It is also conjectured that children will adhere to health attitudes and habits into adulthood (Totura et al., 2015). Due to the recent emergence of type 2 diabetes among children, prevention or delayed onset of the disease is vital.
Various programs have therefore been designed and launched to address T2DM among school-attending children (DeBar et al., 2011).
According to the literature, the evaluation of health interventions is essential for two main reasons: i) improving programmes; and ii) improving policy (Glasgow & Linnan, 2008; as cited in Pansier & Schulz, 2015). Evaluation may help improve programmes and their outcomes by adjusting programme content, identifying the best strategies for increasing participation and adherence, addressing problems and identifying the most effective methods. Evaluation may also help advocate for the programme and mobilize health authorities' support to implement policies and trigger action (Pansier & Schulz, 2015).
When designing effective preventive interventions among school children, it is important to identify modifiable risk factors such as diet, physical activity and physical inactivity as well as theories of behaviour change, the setting and ecology, and policies and organisational factors surrounding the school children. Pansier and Schulz (2015) in their systematic review highlight that most school T2DM intervention programs had inadequate methodologies and had mixed results. The review concluded that further research was needed to define effective diabetes interventions for schools. This was in line with this review as most of the studies have failed to give a clear description of the programs behind the intervention design. The current review observed that locally available resources such as indigenous foods are underutilised especially in Africa as a preventive strategy for T2DM, as no study showed their utilisation despite the fact that food types differ from region to region. Thus, a diet adopted from one region for example may not be effective in another. The current review also identified a dearth in programs and literature on the prevention of T2DM, especially in Africa. These were identified as a gaps that needed to be explored further. Therefore, the aim of this review was to explore global literature concerning the various strategies utilised in the prevention of type 2 diabetes mellitus among school children and their effectiveness.

Method
A comprehensive search of global literature was performed in international scientific databases. The search considered any full-text peer-reviewed research studies around the world relevant to the topic.
The PICO (Population, Intervention, Comparison and Outcomes) was used as the searchable format for the clinical question and to review the titles and the abstracts relevant to the study. Reference lists of included studies and key reviews in the area were also manually searched for additional articles. In order to exhaust the search databases among those selected, those which made provision for related articles were also explored. To determine the eligibility of the article for inclusion in the study, all identified literature was screened using the Sackett's level of evidence hierarchy system (Sackett, 1989) and only randomised controlled trials were considered.

Inclusion Criteria
Only literature published in the English language from 2009 to 2019 was considered. Descriptive studies focusing on the needs of school children with diabetes or identifying the gaps in diabetes care in school were excluded. The study considered only randomised controlled trial (RCTs) with a comparison arm or control group and with or without additional behaviours other than diet and physical activity and had clearly outlined outcome measures. Only studies with preventive/intervention programs and focused on school children aged between 9 to 18 years (grades 5 to 8 in upper primary or middle school) were considered. Studies focusing on other forms of diabetes other than type 2 were excluded. Studies focusing on children with diabetes or prevention programs outside the school, such as summer camps or paediatric centres, were also excluded. However, some of the relevant information of some excluded studies was used in the background of this study. The final review of all the identified literature was conducted by professional independent reviewers to minimize bias.

Models and Type 2 Diabetes Mellitus OR glucose OR HbA1c and Prevention and Schools OR
Schoolchildren OR Paediatrics OR Preadolescents. Boolean operators "and" and "or" were used in some databases. Other databases did not produce any results except the ones given in Table 1.

Search Results
The search generated a total of 26 618 articles of which 17 were removed due to duplication. Of the 26 601 that remained, 22 were found relevant to this topic and were retained for methodological assessment. A total of 26 590 articles were excluded because they did not conform to the objectives and inclusion criteria of this review. Details of the search results are illustrated in Figure 1.

Assessment of Methodological Quality
After selection of the 22 studies presumed to be of acceptable designs, the Critical Appraisal Skills Programme (CASP) tool (CASP, 2018) was used to assess their methodological quality. The CASP for randomised controlled trial was used as only randomised controlled trials were retained. The CASP for randomised controlled trial assesses articles based on 11 questions, hence having scores ranging from 1-11 (Guyatt, Sackett, & Cook, 1994). The scores are classified as good if an article scores between (8-11/11), moderate (5-7/11) and poor (1-4/11). Of the 22 retained articles, 11 had good methodological quality and were finally included in the review ( Table 1). The other 11 that were initially found relevant to the review were later excluded as they did not meet the methodological quality.

Results
The 11 studies included in the review were all randomised controlled trials. Most of the studies included (90%) were carried out in North America (7 from USA and 2 from Canada) with 10% (1) from New Zealand and non from Europe, Asia and Africa. Most European and Asian studies failed to meet the inclusion criteria as they mainly focused on either treatment and not prevention or an older age group (adolescents). Studies found about Africa were mostly about prevalence or prevention of T2DM in the age group above 18 years. All the studies included in this review were carried out among school going children. The sample of the participants in the included studies ranged from 65 to 4603 with the age group ranging from 9 years to 18 years and the sample mean age of 13.5 years.

Outcomes
Six of the studies reported significant improvement in physical activity performance and knowledge in the intervention group compared to the control group with results significant at P<0.05 or less (P<0.01), CI 95% (Cline et al., 2014;Muzaffar et al., 2014;Rush et al., 2014, Contento et al., 2010Slawta & DeNeui, 2010;Grey et al., 2009). Four of the studies reported significant improvements in choice and knowledge of healthy nutrition/diet in the intervention group than the control group with results significant at P<0.05 or less (P<0.01) and CI 95% (Cline et al., 2014;Eskicioglu et al., 2014;Contento et al., 2010;Slawta & DeNeui, 2010). Six studies reported significant changes in BMI between the groups with results significant at P<0.05 or less (P<0.01) and CI 95% (Eskicioglu et al., 2014;Rush et al., 2014;DeBar et al., 2011;Singhal et al., 2011;Foster et al. 2010;Grey et al. 2009). Three studies reported significant changes in waist circumference (WC) at P<0.05 or less (P<0.01) and at a CI of 95% when comparing intervention from control groups (Eskicioglu et al., 2014;Singhal et al., 2011;Foster et al., 2010). A study by Grey et al. (2009) reported significant changes in triglyceride levels with reductions significant in the intervention group at p = 0.012 compared to the control. One study reported a significant reduction of body fat between the intervention and the control group at t (46) = −2.07; P< 0.05; r2 = .08 (Slawta & DeNeui, 2010). A study by Singhal et al. (2011) showed that b-Cell function (HOMA-bCF) and Disposition Index (DI) were significantly higher (P= 0.037); (30.3 73.4; P < 0.037) in intervention group respectively, whereas high sensitivity C-reactive protein (hs-CRP) was significantly lowered (P < 0.001), compared to control group with decrease in homeostasis model

assessment of insulin resistance (HOMA-IR).
These studies measured outcomes associated with the prevention of T2DM and showed significant improvements post intervention. A summary of the findings of the studies included in this review is illustrated in Table 2.
Nutritional education occurred in all the studies as a combination of dietetic counselling and/or basic nutritional knowledge, consumption of high quality to low quality food, such as water, fruits and vegetables instead of sweetened drinks, packaged snacks and fast foods, and change in canteen menu, foods and beverages in the school environment. Four studies involved communication strategies and social marketing (DeBar et al., 2011;Singhal et al., 2011;Foster et al., 2010;Venditti et al., 2009) by utilising peers, posters, banners and branding (Singhal et al., 2011;Foster et al., 2010;Venditti et al., 2009).

Efficacy of Programs
A variety of school based prevention strategies/interventions were implemented in various countries with non-found in Africa, therefore making it difficult to generalise the results especially in the African context. In some studies, sampling and sample sizes were limited as some studies either lacked a contemporaneous comparison group (Rush et al., 2014), had a small sample size (Grey et al., 2009)  these studies failing to adequately address mediator effects. Other studies used tools with low internal consistency to measure food choices & self-efficacy for physical activity therefore making replicability of the study difficult (Grey et al., 2009). Some studies lacked follow-up post intervention (Rush et al., 2014) which provided less evidence of effectiveness of intervention. Intervention in some studies was facilitated by staff and funds provided hence efficacy of such studies cannot assess feasibility, effectiveness or sustainability of an intervention program outside the study setting (Foster et al., 2010).
A study by Singhal et al. (2011) which incorporated ecological and parental support among various intervention facets had more positive outcomes and should hence be considered for developing future T2DM based interventions. Therefore, comprehensive evaluation of school-based diabetes projects will contribute to adjusting and improving the effectiveness of prevention/intervention as well as serve as an advocacy tool for improving school policies on T2DM among school children. A summary of the findings of the studies included in this review is illustrated in Table 2.

Conclusion
This review responds to the call that type 2 diabetes is on the rise among school children and requires attention as shown by the number of preventative/ interventional studies conducted in various parts of the world. In order for preventative approaches to achieve sustained success, the target populations must be empowered to possess a sense of ownership of the process of adopting healthier lifestyle behaviours. Designing a preventative strategy for type 2 diabetes among children requires particular emphasis on theoretical constructs that engage in interactions of personal, social and environmental factors and interactions should promote the adoption of healthful behaviours in a supportive, meaningful and personally enjoyable context. The review shows that it requires various integrations of interventional elements including dietary education/counselling, physical activity, diabetes knowledge, competence building, social marketing, social as well as community support and environmental factors being considered concurrently. The review has shown further that there's still a dearth in research and information on the prevention of type 2 diabetes mellitus among school children, especially in Africa.
Therefore, more studies of sound methodological quality exploring this area need to be done.