Self-Determination Theory and Quality of Life of Adults with Diabetes: A Scoping Review

Background Diabetes is one of the leading causes of sickness, death, and decreased quality of life globally. The prevalence of diabetes keeps rising globally due to lifestyle changes and urbanization. Therefore, improved quality of life (QoL) and appropriate diabetes self-management practices, including treatment adherence, are crucial to improving and sustaining the health of diabetic patients. Some studies have adopted the self-determination theory (SDT) to study diabetes interventions, but less is known about its effectiveness in improving QoL, treatment adherence, and diabetes self-management. Aim/Objective. This review assessed the effectiveness of SDT in improving self-management practices, treatment adherence, and QoL among adult diabetic patients. Method We followed the six-stage framework by Arksey and O'Malley in conducting the review. PubMed, JSTOR, Central, and ScienceDirect databases were searched for published articles from January 2011 to October 2021 using keywords and Boolean logic. Furthermore, we screened a reference list of related articles. Also, Google Scholar, Z-library, and web-based searches were carried out to retrieve other relevant evidence that applied SDT in improving QoL, diabetes self-management, and treatment adherence. Findings. Fifteen studies met the inclusion criteria, from which data were extracted as findings. SDT effectively improved QoL, diabetes treatment adherence, and diabetes self-management among diabetic patients. Of these studies, 11 provided data on SDT and diabetes self-management and affirmed the effectiveness of the theory in improving appropriate diabetes self-management practices. Two studies confirmed the effectiveness of SDT in improving treatment adherence. SDT and QoL were assessed in 4 of the studies, which demonstrated the effectiveness of SDT in enhancing the QoL of diabetic patients. Conclusion SDT effectively improved QoL, diabetes treatment adherence, and diabetes self-management. The application of SDT in diabetes management will improve the health and QoL of diabetic patients. Hence, diabetes management interventions could adopt SDT to guide treatment.


Introduction
Diabetes is one of the leading causes of sickness, decreased quality of life (QoL), and deaths worldwide [1]. It is also among the top 10 causes of death globally [2,3]. Besides, diabetes is a chronic noncommunicable disease (NCD) that occurs when the pancreas produces insufficient insulin (the hormone that regulates the body's blood sugar level) or the body cannot effectively utilize the insulin produced [4]. Thus, diabetic patients usually take insulin daily to help absorb food nutrients into their system [5]. Globally, there were about 476 million diabetes cases, of which the incidence was about 22.9 million in 2017 [6]. Accordingly, over 1.37 million people died from the disease and its complications, with over 67.9 million disability-adjusted life years (DALYs) in 2017 [6]. The presence of diabetes exposes an individual to a 2-3-fold risk of all causes of death among adults [4]. Moreover, diabetes and cardiovascular diseases (CVD), respiratory diseases, and cancers account for over 80% of premature deaths from NCDs globally [7,8]. Unfortunately, research shows that the condition will rise to over 693 million cases by 2045 if adequate measures, including efforts to ensure adequate self-management practices and medication adherence, are not implemented [9].
Patients with diabetes experience worse QoL than those without chronic diseases [10][11][12]. The QoL (physical and social functioning and perceived physical and mental wellbeing) of diabetic patients are mostly affected due to the management process and the need to adjust to diabetes management demands [7,13,14]. Thus, diabetic patients must consciously balance insulin intake and other management interventions [15]. Moreover, the psychosocial burden of living with diabetes usually affects the self-care behaviour, medication adherence, and QoL of diabetic patients [16]. The main target in diabetes care is maintaining blood glucose levels in a healthy range to avoid long-term diabetes complications through adhering to medications and appropriate self-management [17]. However, studies show low levels of medication adherence [18], poor self-management practices [19], and poor quality of life among diabetic patients [20]. Moreover, it seems there is a dearth of information on the most effective method of improving medication adherence, appropriate self-management practices, and QoL among diabetes patients [16].
Studies employed self-determination theory-(SDT-) based interventions to improve medication adherence, selfmanagement practices, and QoL of diabetic patients [21][22][23][24]. The theory consists of three psychological needs, relatedness, competence, and autonomy, for optimal functioning [25]. Autonomy consists of diabetic patients' experiences and perceptions of control and self-initiation in line with their idea of self [26]. Additionally, competence develops from the need to be effective in diabetes management practices and the praise or appreciation of such excellence. Also, relatedness involves the need to "experience love and care as well as to express love and care towards others" [27].
Besides, the SDT improved the quality of life of diabetes patients in Norway [28]. Also, Raaijmakers et al. [29] found that self-determination regarding type 2 diabetes care contributed to improved QoL. Moreover, the SDT improved physical activities among diabetic patients in France [30] and Uganda [31]. Although studies have linked some constructs of the SDT and QoL of adults with diabetes, the effectiveness of SDT in improving the QoL and self-management practices of adult diabetic patients is not pronounced in the literature. This scoping review examined available evidence on the link between SDT and QoL of adults with diabetes.

Methods
This scoping review was conducted following the six-stage framework by Arksey and O'Malley [32]. The framework was adopted because it helps to assess the literature to examine what has been done and identify the gaps in knowledge that need attention [33]. Arksey and O'Malley [32] suggest that the following stages should be followed in conducting a scoping review: (1) identifying and stating the research questions; (2) identifying relevant studies; (3) study selection; (4) data collection; (5) data summary and synthesis of results; and (6) consultation.
In the first stage, we identified and drafted the research questions to guide the study: (1) How effective is SDT in improving diabetes self-management? (2) How effective is SDT in improving treatment adherence? and (3) How effective is SDT in improving the QoL of adult diabetic patients?

Identification and Selection of Studies
3.1. Search Strategy. Two authors (PO and HKK) conducted a preliminary literature search on the topic to set the inclusion and exclusion criteria. Furthermore, we expanded and refined our search strategy with expert help (an academic librarian at the University of Cape Coast). In addition, we conducted a vigorous literature review of published articles in four electronic databases (PubMed, JSTOR, Central, and ScienceDirect). We expanded the search via hand search to include other unpublished sources. The search strategy included literature from January 2011 to October 2021 using key search words and Boolean logic. Also, a free web-based search was conducted to retrieve other relevant materials. Also, Google Scholar and Z-library were searched for additional records. Furthermore, reference lists of eligible records were checked for other relevant articles.
The final search was completed on October 28, 2021. Titles and abstracts of studies retrieved were read, and only studies relevant to the study were considered. Six keywords were used in the search strategy: ("Self-determination Theory" OR "diabetes" OR "Application of Self-determination Theory" OR "QoL" OR "Diabetes self-management" OR "Diabetes medication adherence) AND ("Adults" OR "grownups" OR "people aged 18-75 years" OR "grown people").

Eligibility
Criteria. Studies were included if conducted among adult diabetic patients (type 1, type 2, and gestational diabetes), aged 18-75 years, measured at least one SDTbased motivational construct, and published online between January 2011 and October 2021 (with no limit concerning the start date). Also, the authors must have explicitly mentioned SDT as the framework for a study to be included.

Exclusion Criteria.
We excluded studies that did not specify the study population and those that were not published in English. Additionally, nonprimary studies (systematic reviews and scoping reviews) and studies that used SDT-based measures but employed motivational interviewing as their guiding framework with no reference to SDT were excluded.
3.4. Procedure. We used the eligibility criteria of the current study to scan the titles and appraise the abstracts of the identified literature for full-text review. We further scanned and manually screened the references of all included literature to add relevant studies to our review. Two of the current study's authors (PO and HKK) did the full-text review independently. The authors later met, reconciled the differences, and agreed on the included studies. We then developed a data extraction sheet with the following categories: author, year of publication, study title, country, population, study design, sample size, sampling strategy, and summary of findings (see Table 1 in the Appendix). Three of the study's     authors (PO, HKK, and JOS) extracted the data independently. They later settled the differences to obtain a final result for the study. We involved third (EWA) and fourth (PYAA) reviewers to settle differences where there was disagreement in the findings of the three authors. One of the authors (PO) drafted the final extracted table (Results). All the authors read through the final draft results and ensured the findings reflected the agreed results. We finally carried out a thematic analysis and synthesis and presented the results. Additional consultations were made with subject experts to enhance the review. We used the PRISMA flow diagram to keep records and also screen the identified records (see Figure 1).

Results
The initial search in JSTOR, PubMed, Central, ScienceDirect, Google Scholar, Google, and Z-library produced 28,909 records (JSTOR = 30, PubMed = 83, Central = 7,031, ScienceDirect = 4,353, Z − library = 12, and Google Scholar = 17,400). Additional 16 records were identified through other sources. After removing duplicates using the Mendeley software, 15,058 records were available for screening. Furthermore, 185 pieces of literature qualified for full-text anal-ysis for eligibility. We finally used 15 full-text studies in our thematic analysis and synthesis ( Figure 1 details the screening process).

Characteristics of Included Studies.
The included literature includes studies conducted among diabetic patients 18-75 years old using SDT to determine or improve QoL, diabetes self-management practices, and diabetes medication adherence. Out of the 15 included studies, five were experimental studies, one was a descriptive explorative qualitative study, five were cross-sectional studies, and one was a longitudinal study ( Table 1 in the Appendix). Four studies addressed SDT and QoL among patients with diabetes, two explored SDT and treatment adherence, and 11 focused on SDT and diabetes self-management practices. Based on the research questions, three main themes were derived from the reviewed studies: (1) SDT and diabetes self-management; (2) SDT and diabetes treatment adherence; and (3) SDT and QoL among diabetic patients.

SDT and Diabetes
Self-Management. Eleven [34] studies applied SDT to improving diabetes self-management. Lack of autonomy hindered diabetes self-management [35]. Also, autonomous motivation, perceived competence, and  Journal of Diabetes Research relatedness influenced the higher frequency of vigorous PA among people [31]. The application of SDT was effective in improving PA among diabetic patients in five studies ( [11,30,[36][37][38]). Besides, SDT was also influential in improving dietary self-care among diabetic patients [39] (see Table 1 [Appendix]).

SDT and Treatment
Adherence. The adoption of an SDT-based intervention effectively motivated diabetic patients to comply with lifestyle recommendations and avoided noncompliance behaviours in one study [40]. Also, SDT-based intervention predicted that patients with less intrinsic motivation and a low relatedness score report a higher rate of nonadherence to diabetes treatment [41].

SDT and QoL of Patients with Diabetes.
We summarized the findings on the effectiveness of SDT in determining or improving the QoL of diabetic patients. A study revealed that diabetic patients who did not receive autonomy support from their healthcare providers experienced anxiety about their health status and frustration with the care quality [35]. Also, patients who engaged in SDT interventions experienced new life possibilities and accepted their condition [28]. Further, diabetic patients who participated in the SDT intervention reported relatively dominant control motivation to comply with lifestyle recommendations and experienced improved health and QoL [40]. Also, diabetic patients who participated in the SDT intervention developed increased self-esteem. and vice versa [42] (see Table 1 in the Appendix).

Discussion
This scoping review determined the effectiveness of SDT in improving the QoL of diabetic patients. Our paper also explored the effectiveness of SDT in improving treatment adherence and appropriate self-management practices among diabetic patients. We highlighted several findings. Firstly, we found that a lack of autonomy support impedes diabetes self-management, whereas the autonomy support component of the SDT effectively improved PA among them. Secondly, SDT effectively increased appropriate dietary self-care practices among diabetic patients. Thirdly, SDT interventions effectively guided diabetic patients to develop the willingness, mastery, and connection to comply with prescribed medication and treatment methods. Fourthly, diabetic patients in SDT interventions developed the dominant controlled motivation to comply with their recommended medications. Lastly, SDT was effective in improving the QoL of diabetic patients.

SDT and Diabetes
Self-Management. We found that a lack of autonomy support impedes diabetes selfmanagement and that the autonomy support component of the SDT is more effective in improving PA and appropriate dietary self-care practices in diabetic patients. Our findings agree with studies conducted in South Africa [35] and China [34]. The diabetic patients in the South African study who received no adequate autonomy support from healthcare providers experienced more difficulty in effec-tively managing themselves than those who received autonomy support. However, there was an increase in diabetes self-management scores among autonomous support groups in the Chinese study. The similarities could be that when diabetes patients feel more autonomous (are willing to initiate an action without being forced to do so) in their management process, they tend to take control of their management process [38]. Typically, diabetes patients are challenged with the high cost of healthy foods, difficulty in giving up on unhealthy lifestyles, busy work schedules, side effects of medications, and accessibility of diabetic management services [43]. Perhaps autonomy support increases their willingness to continue appropriate management practices despite their challenges. The current findings imply that diabetic patients need a sense of desire to comply with diabetes self-management protocols to improve their health. However, contrary to the present results, Liu et al. [34] found autonomy support insufficient to promote appropriate selfmanagement practices among diabetic patients, but other factors such as self-efficacy, knowledge, skill, family, and peer support. Also, the current finding where autonomy supports improved PA is similar to that of other studies [31,37,38,44] which reported higher PA among people with autonomy support and low PA among those with no or less autonomy support. Perhaps people who receive autonomy support engage in PAs willingly to satisfy their desires [45]. This finding may imply that diabetes self-management interventions that fail to provide autonomy support to their patients could experience a decrease in appropriate self-management practices among their participants.
Furthermore, we found that SDT (competence, relatedness, and autonomy) effectively increased appropriate dietary self-care practices among diabetic patients. Nouwen et al.'s [39] findings affirm those of the current study. They found diabetes patients in SDT intervention adopt healthy dietary practices. Perhaps SDT-guided diabetes management interventions promote patients' autonomy and help develop skills for healthy dietary patterns.

SDT and Medication
Adherence. We found that SDT interventions effectively guided diabetic patients to develop willingness, mastery, and connection to comply with prescribed medication and treatment methods. Our findings are similar to those of other studies [40,46]. This finding could be because SDT-based interventions equip diabetic patients to own their management interventions, feel supported, and help them develop competence in their management programs [44,47]. However, Rajab et al. [41] found otherwise in their study. They found that patients with low autonomy and relatedness scores did not comply with their medication due to poor intrinsic motivation and relatedness [41]. Probably, when diabetic patients satisfy autonomy (free will), develop mastery (competence), and feel love and care from family and healthcare providers, they are more likely to comply with their medications and treatment routine that could improve their health and QoL. Also, contrary to our findings, Aloudah et al. [46] found higher treatment adherence among diabetic patients who observed others adhering 9 Journal of Diabetes Research to their treatment routines than those in SDT intervention. The divergent views call for a combination of therapies, such as SDT and imitation, to achieve treatment adherence and attendant health-improved outcomes in patients.

5.
3. SDT and QoL among Diabetic Patients. We found that SDT effectively improves the QoL of diabetic patients. This finding could be because the theory improves patients' competencies, guides them to take voluntary actions, and makes them feel loved and supported [42]. Our finding implies diabetic patients could develop a high QoL if SDT guides diabetes management interventions. Our finding aligns with other studies [12,35,40,42,48]. These studies reported that diabetic patients in SDT interventions developed new life possibilities and exercised control over their new lives.

Limitations
This scoping review has provided insight into the effectiveness of SDT in improving QoL, diabetes treatment adherence, and diabetes self-management. However, there are a few limitations to the study. We included only open-access articles that were published in English. There is a possibility that we missed some vital literature.

Conclusion
The application of SDT can effectively improve appropriate self-management practices among diabetic patients. This implies that when interventions are implemented to enhance the autonomy, competence, and sense of connectedness (relatedness) among diabetic patients, they are more likely to adhere to the recommended diabetes self-management practices. This means that the economic burden on diabetes management, morbidity, and mortality cases associated with diabetes may be reduced globally. Furthermore, SDT was found to be effective in improving diabetes treatment adherence. Therefore, should SDT be used in daily diabetes care and interventions, more patients with diabetes may comply with diabetes medications and other treatment routines. We theorized that adopting SDT in the diabetes management process may improve patients' mental, social, and physical well-being and enable them to contribute effectively to society.

Data Availability
All papers included in this work are available online and can be accessed based on their Open Access policies.

Ethical Approval
The study was conducted per the established reporting standards for reviews. We also worked following the standards of the Helsinki Declaration of 1975, as revised in 2008.