Introduction
Bariatric surgery has been shown to be effective for long-term weight loss and as a treatment for obesity-related comorbidities, but it is associated with various micronutrient deficiencies [
1]. Hypovitaminosis D is one of the most common deficiencies experienced after bariatric surgery, and the deficiency is multifactorial, with some factors related to obesity and others to nutrient malabsorption [
2]. Little is known about nutritional deficiencies in adolescents, but nutritional risks have previously been described as higher among adolescents undergoing bariatric surgery than among adults. These differences may be explained by adults having better adherence to post-surgery supplementation [
3‐
5]. Supplements are routinely recommended to minimize the possible risk of nutritional deficiencies [
6], and daily supplementation of multivitamins including calcium and vitamin D is believed to be a long-term requirement for post-bariatric surgery [
7]. However, there is some disagreement about supplementation due to the high variability in the response to vitamin D supplementation in patients who have undergone bariatric surgery. This may be explained by individual body fat levels and degrees of malabsorption [
2].
Behaviour that dictates adherence to medication recommendations is complex, and since the 2003 World Health Organization’s report on adherence, little has improved with adherence levels, which are estimated to be 50% [
8].
Barriers for adherence to supplementation recommendations after bariatric surgery have been reported before, and “difficult to remember” and “trouble taking all the tablets” were identified as two important barriers [
9]. Some researchers have compared adherence with vitamin supplements in adolescent and adult bariatric populations [
10,
11], and rates of vitamin adherence have been as low as 30% 6-month post-surgery in adolescents [
10]. In adults, self-reported non-adherence was associated with lower vitamin levels [
11]. In a recently published study, 38% of adolescents had low levels of vitamin D compared with 24% of adults, with the difference being explained by the younger patients’ lack of adherence to vitamin supplementation recommendations after surgery [
4].
It has been suggested that adolescents adhere better to recommendations that have immediate consequences if they are not followed than those that have less obvious benefits or that are intrusive to their lifestyle [
12]. However, rates of adherence in adolescents vary widely, and a lack of consistency in measurements may contribute to this variation [
13]. Non-adherence to recommendations after bariatric surgery has been linked with poorer outcomes, and adherence may be a key to a successful outcome [
14]. Preoperative predictors of adherence to dietary and physical activity recommendations have been studied, and this research has highlighted the importance of preoperative psychosocial preparatory work [
15].
The long-term risks of bariatric surgery are not well identified, especially the skeletal risk where vitamin D deficiency may play a part in increased bone mineral density loss after bariatric surgery [
16], and a detailed understanding of the long-term nutritional effects of the surgery in this age group is limited. Therefore, it is of clinical importance to acquire coherent knowledge on whether adolescents do what they say they do and barriers and facilitators to following prescribed recommendations, in order to be able to provide support to these individuals.
The purpose of this study was first to measure the accuracy of self-reported adherence to supplementation recommendations by using objective measures of vitamin D levels in blood and thereafter to explore perceptions on barriers and facilitators to adherence to supplementation recommendations.
Discussion
Our study was based on two different methods to describe adherence to supplementation recommendations after bariatric surgery to determine the convergence between self-reported adherence and vitamin D status and explore the reasons behind insufficient adherence.
The results in our study show convergence of self-reported adherence and levels of vitamin D. Two categories emerged in the analysis: awareness and personal capability and external factors. It was clear that it was crucial if you had insight into why the supplements were prescribed and for what reason. Most of the participants stated that they did not take their supplements because the tablets were large and there were so many. A clear facilitator was whether there were people or social circumstances that motivated them.
Some previous studies have reported blood levels of vitamin D as a proxy for adherence but did not report the relationship between blood analyses and self-reported adherence [
13]. Our results indicate that self-reported adherence is concordant with blood analysis, indicating that the participants who stated that they followed the supplement recommendations answered truthfully.
Some studies have shown that self-reported adherence can be a predictor of clinical outcomes in patients with other diagnoses [
25], while other studies have reported no correlation between self-reported adherence and objective measurements of adherence [
10]. However, a high proportion of participants in our study, approximately 50%, were non-adherent patients, which is in line with a previous observational and intervention study, especially in adolescents as younger age groups are linked to lower adherence levels [
7]. A previous study of adults reported adherence to vitamin D supplementation to be good just after surgery (90%) with regular follow-ups and nutritional advice, but this rate dropped to approximately 50% 1 year after surgery [
26].
Our qualitative evaluation resulted in an overarching theme to describe facilitators and barriers: Capacity is crucial for adherence in youth who have undergone bariatric surgery.
Self-efficacy and social power have been described as central to adherence [
27]; therefore, in order to understand our results, we have used a framework based on this concept [
28,
29]. Self-efficacy is described as one’s feelings and thoughts about one’s capability [
28]. Power in healthcare may be described as “the capacity to participate knowingly in change” and consists of four inseparable dimensions―awareness, choices, freedom to act intentionally, and involvement in creating change [
29, p 48–49]. In this context, social power, including referent power, may be relevant, which is a person with the ability to be a frame of reference, for example, a parent or partner [
27].
Maturity and personality are highlighted as prominent factors in remembering to follow prescribed supplementation. Maturity is a factor that has been shown to influence decision-making in adolescents with type 1 diabetes [
30]. Crucial factors in being able to make decision-making in a medical context are communicating a choice, understanding, reasoning, and appreciation. In favourable environmental circumstances, this may be possible at the onset of adolescence; however, the reward system of the brain develops early, and the development of the control system occurs late, which reduces the capacity for decision competence for adolescents in specific situations [
31]. From this, it can be concluded that even adolescents with high capacity need support in their decision-making, which emerges as favourable in the results. Several of those who described that they have strategies for their supplementation emphasized the importance of relatives or other important people supporting and reminding them. This is in line with earlier findings that have shown that support from parents and partners can have a positive effect on adherence [
32]. Enhanced adherence ought to be achieved if parental and partner involvement (referent power [
27]) is included in care to strengthen external motivation.
A distrust of treatment or healthcare providers is known to lower adherence [
33], which may come from a lack of health literacy [
33,
34] or participants receiving conflicting information from different healthcare providers, the media, or the Internet [
35]. Some participants in this study expressed a distrust of the supplements and suggested that it is more effective and natural to eat a varied diet with a lot of vegetables. However, this highlights the need for healthcare providers who have knowledge of this specific group of patients to provide consistent information [
36]. Due to the high prevalence of non-adherence to supplementation recommendations after bariatric surgery, healthcare providers should take time to discuss adherence with a focus on problem-solving and different predictors for each individual in an effort to improve adherence.
Our participants described knowledge and understanding as being of importance to adherence, which is in line with a recently published review that pointed out the value of providing clear and consistent information to patients about postoperative lifestyle behaviours [
13]. The long-term effectiveness of real-time medication monitoring combined with text message reminders has been shown to improve adherence in adults with type 2 diabetes [
37]; however, several educational interventions have only shown modest success in improving adherence to treatment recommendations across chronic diseases [
38].
Previous research describes two main barriers for adherence to supplementation recommendations after bariatric surgery: difficulty in swallowing pills and forgetting to take supplements. This is consistent with our results [
9,
10]. Taking supplements at a set time each day, keeping them in a visible place, using pill organizers, and/or setting an alarm were some of the factors recommended by participants that helped them to remember to take their supplements. They described better adherence if there is a daily routine which is in line with a recent study [
33]. In summary, they are well aware that they have a choice and can act intentionally.
Cost was mentioned by our participants as a barrier due to participants having to pay for the supplements themselves. Thus, an additional approach could be to balance the financial cost against the cost of nutritional deficiencies and to educate patients about the risk of not taking supplementation. Thus, studies have shown that even when medicine is free or co-pays are decreased, lowering costs has only a small influence on improving adherence [
39].
Barrett describes power as “the capacity to participate knowingly in change” (awareness, choices, freedom to act intentionally, and involvement in creating change) [29, p 48–49], and in our study, most of the participants have an awareness of that they ought to take their supplementation and which barriers they are experiencing, as well as facilitators. Our study clearly shows that participants are aware that it is they themselves who are creating the change.
This study has several potential limitations including the quantitative cross-sectional design with a small sample size that does not permit a casual interpretation of results. The classification of the direct method measuring adherence may be discussed, but our clinical experiences support the different categories of adherence. Uncontrolled factors such as reduced bioavailability related to obesity, impaired absorption after surgery, and preoperative deficiencies may have influenced our results.
In the qualitative analysis, the authors have strived to obtain trustworthiness (credibility, confirmability, dependability, and transferability). The participants and context are described in as much detail as possible, all authors have been involved in the analysis, and the analysis process is described in as much detail as possible. Furthermore, quotations have been used in the results to strengthen trustworthiness [
40]. One strength of the qualitative part of the study is that all participants in the AMOS study from the greater Stockholm area were asked to participate, which resulted in a 50% acceptance rate. For the interview study, nearly 50% of adolescents who had undergone bariatric surgery in the Stockholm region participated in the interview study, which strengthens trustworthiness. However, it is a weakness that they primarily come from urban areas, and this may weaken transferability.
Further studies are needed to understand in more depth the importance of young adults’ awareness and capacity to participate in change. It would be of importance to explore whether the involvement of important people in their lives would affect their ability to adhere to recommendations.
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