**1. Introduction**

Self-management [1] is of key importance in the successful treatment of patients with chronic conditions, such as Type 1 diabetes (T1D), a condition in which the patient needs daily insulin treatment because their body fails to produce this hormone. In contrast to Type 2 diabetes, T1D is typically diagnosed at a young age when patients are still dependent on their parents who are responsible for managing their child's health condition [2]. Children are supposed to gain more responsibility for their T1D care when they become adolescents. Goals for the management of T1D include achieving optimal glycemic control, avoiding acute complications, and minimizing the risk of long-term microvascular

and macrovascular complications. Self-monitoring of blood glucose (BGM), either by using a blood glucose meter or using a system for continuous blood glucose monitoring [3] is one of the most important activities in managing diabetes. Research repeatedly shows that adherence to BGM is linked to glycemic control in pediatric T1D [4–7]. That is, the more frequently the patient measures their blood glucose (BG) using reliable, certified blood glucose meters [8], the more their BG will be within acceptable and appropriate levels. International studies show that metabolic control is unsatisfactory in many adolescents with T1D [7,9]. Despite advances in technologies that support BGM, frequent measuring is still a burden for many children and adolescents [10–12]. Adherence, i.e., the degree to which the person's behavior corresponds with the agreed recommendations from a health-care provider, is a key factor in the successful treatment of chronic conditions. Even when patients have good knowledge about treatment adherence, their actual practice of adherence is often less than ideal [13]. One of the factors that is often underestimated in T1D management is the burden of the disease in everyday life. The patient is constantly required to perform actions and make decisions in their daily diabetes routine. Examples are: finger pricks for glucose measurements, insulin injections, replacing needles for insulin pumps or subcutaneous glucose sensors, carbohydrate counting, and regime adjustments for physical activities or sports, for sick days, for parties, etc. These requirements interfere with normal life, especially for adolescents who want to be perceived as "normal". Aversion to these compelling actions often means that children and adolescents do not achieve a good metabolic control. Research on the motivations for and causes of non-adherence to diabetes care regimens among adolescent diabetes patients points to the contrasting views on adherence between patients and providers. Where providers typically view adherence in pursuing optimal glycemic control and health outcomes, patients have other perspectives [11]. Hence, one of the adherence challenges with T1D is motivating and helping these patients measure their BG at regular times every day in such a way that it is least invasive using methods and tools popular among this target group. Digital coaching systems that monitor the users' BGM send reminders and motivating messages to support the patient adhere to a personalized and clinically appropriate medical regimen. However, to function properly these systems need regular data from the user, which often requires additional actions on the part of the user; e.g., upload glucose data. The challenge is then to motivate the patient to keep using these tools on an ongoing regular basis. How can technology help these patients to make it a bit easier to learn to live with their condition and to adhere to a medical regimen as long as there is no cure?

The pervasive gamification and coaching platform presented here is the product of the EU Horizon 2020 PERGAMON project (No. 644385) in which a number of developments came together that exploit opportunities offered by the availability and acceptance of new technologies in e/m-health: reliable wearable sensors, mobile apps that support self-management and lifestyle behaviour change, digital coaching, serious games and gamification to enhance healthcare education, and Patient Web Portals connected to Personal Health Records, that allow patients to upload personal data and receive personalised guidance from caregivers. The platform integrates the complementary potential offered by the widespread use of wearable sensors and mobile devices and the popularity of games and social networks delivered on a secure and authorized portal that supports patients and their caregivers in self-management of their chronic condition. Reviews of studies in the development and evaluation of the use of each of the above mentioned component technologies show besides (potential) positive impact on diabetes care and opportunities, that there are also challenges that demand a more integrated solution [14].

The management of diabetes is complex and patients need personalized advice and medical control by a pediatrician or diabetes nurse. The growing number of diabetes patients worldwide place a heavy burden on medical budgets. Patient web portals are increasingly set up and maintained by hospitals to support self-management and improve communication between patients and their medical caregivers, as one of the most important predictors of adherence [13]. A review by Osborne et al. showed that they have a positive impact on management for diabetes care [15]. The communication

between health provider and patient could benefit from integration of these web portals with the mobile technology and "real-time" sensoring available on smartphones.

What can we say about quality, engagement and effect in terms of adherence when treatment is supported by mobile diabetes apps? While a wide selection of mobile apps is available for self-management of diabetes, some specifically designed for patients with T1D [12], some with a virtual coach [16,17], current research suggests that most do not meet basic requirements for medical applications [18]. From a medical perspective a main finding from a review by Chomutare et al. [19] is that a critical feature strongly recommended by clinical guidelines, namely, personalized education, is not present in current applications. Although mobile health apps have great potential for improving chronic disease care, they face a number of challenges including lack of evidence of clinical effectiveness and lack of integration with the healthcare delivery system. There is a clear need for formal evaluation and review of potential threats to safety and privacy [20]. Brzan et al. [18] reviewed 65 apps for diabetes and concluded that 56 of these apps "did not meet even minimal requirements or did not work properly". They report on a qualitative study in young adults with the objective to explore their experiences with apps that aim at health behavior change and their willingness to use these apps. Many participants in their study "were not motivated enough to regularly and precisely use the apps in making healthy lifestyle changes", a recurring issue in many studies. Boyle et al. [21], reporting on a survey of patients seen at a hospital diabetes clinic in New Zealand found so many concerning issues that they concluded that there is a need for an app assessment process to raise confidence in the quality and safety of diabetes management apps in diabetes patients as well as in healthcare providers.

Although short term user studies often show promising results in terms of adherence to medical treatment there is no evidence of maintenance of high adherence in the long run. According to self-determination theory, it may take many months before external motivation becomes internalized into daily routine behaviours [22]. Hence there is a need for ways to motivate patients with T1D to manage and adhere to their treatments on an ongoing basis.

Gamification techniques have been introduced as possible means to motivate patients to sustain adherence to medical treatment [23]. Gamification is using elements of game design [24], i.e., points, leader boards, levels, competitions, rewards, achievements, mini games, goals, experience points, rules, narrative, graphics, imagination, role identification, or setting step-wise challenges in pursuit of a goal. Use of games or gamification in health behaviour change programs might thus be a way to intrinsically motivate users to expose themselves to and continually engage with these programs (Baranowski et al. [25], Thompson et al. [26], Cugelman [27]). In serious games, elements of game design [28,29] are used to help the user learn to reach non-game goals. The ultimate goal is to foster intrinsic motivation for learning and maintaining desired behaviours [30].

Educational games in diabetes care dates back to the 90s. Lieberman [31] describes 14 diabetes self-management video games. The games typically involve players in problem-solving and decision-making in simulations of diabetes self-management, usually by asking players to balance food intake and insulin injections to keep a game character's blood glucose within a normal range. An important feature of these games is that they provide practice through rehearsal and show cause and effect, while also providing basic information about diabetes self-management. There are many games that teach the relationship between food (carbohydrates), plasma glucose level, exercise, and insulin dose [32,33], or that focus on learning the number of carbohydrates in drinks, snacks and meals [34]. Several studies using randomized controlled trial designs, e.g., Brown et al. [35] and Fuchslocher et al. [36], showed that diabetes related content explicitly presented in games improves diabetes self-management in T1D. In a study by Lieberman [37] a diabetes game reduced diabetes-related urgent and emergency visits by 77% after young patients had the game at home for six months, compared to no reduction in clinical utilization in a control group of young patients who took home an entertainment video game that had no health content.

In a special issue on Games for Diabetes, Theng et al. [38] provide a review of evidence on the efficacy of video games and gamification in diabetes self-management (not specifically targeting, but including T1D). The duration of most of the ten studies was short with small sample sizes of those that studied patients aged between 8 and 16 years old. All the interventions targeted behavioural changes to promote healthy behaviours among the study participants. Video games were found to be effective tools for education while gamification and virtual environments increased intrinsic motivation and positive reinforcement. Remarkably, their study did not find any research specifically targeting medication adherence as part of the behavioral change process.

Charlier et al. [39] reports a review of randomized controlled trials (RCTs) assessing efficacy of serious games in improving knowledge and self-management in young people with chronic conditions. From 9 studies the general conclusion is that educational video games improve knowledge and self-management. Johnson et al. [40] identify potential advantages of gamification from existing research and conducted a systematic literature review of empirical studies on gamification for health and well-being, assessing quality of evidence, effect type, and application domain. They conclude that due to the relatively small number of studies and a lack of studies that compare gamified interventions to non-gamified versions of the intervention, it is hard to draw general conclusions about the efficacy of gamification in digital health interventions. Deacon and O'Farrell [41] and Sardi et al. [42] come to a similar conclusion: there is still a lack of valid empirical evidence that support the use of gamification strategies employed in e-Health.

Some studies indicate that gamification of BGM has positive effects on BGM in adolescents with T1D [43,44]. In the mobile game, DIAL, a group of children (8–18) were given a mobile device with an integrated motivational game in which the participants could guess a BG level following collection of three earlier readings. In a 4 week experiment, the game group sent significantly more glucose values to the platform than the control group that did not have the game. Use of a motivational game appears to increase the frequency of monitoring, reduce the frequency of hyperglycemia, improve diabetes knowledge and may help to optimize glycemic control. Follow-up research in a RCT among adolescent T1D patients over 12 months showed that app usage diminished over the trial. On average, 35% (16/46) of the participants were classified as moderately or highly engaged (uploaded glucose data 3 or more days a week) over the 12 months. S. et al. [14] suggest exploring the utility of integrating mobile applications for T1D support into routine clinical care to facilitate more frequent feedback.

Does access to video games or the possibility of making progress in a video game work as a reward for regular glucose measuring and control? In a study by Klingensmith et al. [45] acceptance of a system that connects a blood glucose meter with a Nintendo game was assessed in a sample of children, adolescents, and young adults with T1D. Users receive reward points that can be transferred from the meter to the video game, allowing access to new levels of play and mini games. Rewards are based on frequency, timing and results of blood glucose testing. Healthcare providers can also set personalized target ranges in the meter to help patients reach glucose goals. The majority of healthcare providers agreed that the coupled system would solve a problem in diabetes management, and that it would motivate patients to test their blood sugar. They observed an increase of use in the home situation compared to the lab situation because users wanted to have more advanced games [45].

Besides monitoring and feedback, personal coaching and goal-setting and learning how to cope with situations that impact blood glucose level, social support is an important strategy to help young diabetes patients to adopt healthier habits. A rationale for using games for serious purposes like health is their ability to motivate and facilitate social encounters [28]. Children like to play together even when playing single player games. The effect of social support on users' motivation to use mobile apps appears to be mixed. Some are motivated by competition among peers, where others feel that sharing data and results introduces too much competition [46]. The gaming framework of Chomutare et al. [30] focuses on completing self-management tasks, rather than rewards or penalties. They emphasize the value of cooperation, social comparison and a focus on positive achievements as core game elements, limiting the extent of competition. Social media in combination with serious games are suggested as a beneficial platform for self-management of T1D by the younger age groups [47]. Social media are popular among adolescents. They can interact and build communities dedicated to specific games. Social media allow T1D patients to share their game experience with everyone; not only with other patients with diabetes. A disadvantage of such an open community is the lack of a quality control of the content which is mostly provided by the community itself [47]. This is one of the reasons we chose an environment with authorized users where content is moderated by the care institute.

The above review presents a state of the art of existing applications. The PERGAMON platform (introduced in Section 1.1) integrates techniques and design decisions that we find in the applications discussed above. A system that integrates all the diabetes educators by integrating gaming and coaching in a clinical setting through a principled design would overcome many of the shortcomings of the partial solutions in reviewed systems (e.g., no personalization, not specifically focused on medical adherence).
