Overall, adherence to multivitamin therapy for adolescents early in their post-operative course following bariatric surgery is remarkably low at approximately 30%, based on rigorous, longitudinal, objective measurement methodology. Adolescents appeared to take their multivitamins preoperatively and immediately following surgery, but demonstrated declining adherence over the first six post-operative months. Furthermore, they took no multivitamins on 66% of days over this time period. There may be several reasons these adherence data are significantly lower than adherence to medications in other pediatric conditions (e.g., asthma, cystic fibrosis, rheumatoid arthritis), which averages 50% (14
). First, despite education regarding the need for daily multivitamin therapy, this may be perceived as a minor treatment recommendation relative to the significant dietary and physical activity changes prescribed after bariatric surgery. This paradigm is in sharp contrast to the role medications play in other diseases (e.g., epilepsy, diabetes, asthma, and rheumatoid arthritis) for which most patients and parents would not question the primary role of pharmacotherapy. Second, unlike the above mentioned conditions, there are no immediate or overt consequences to multivitamin non-adherence, leading adolescents to believe missed doses are of no consequence. Finally, as discussed below, the barriers to multivitamin therapy following bariatric surgery may be unique. For example, the inability to eat solid foods for several weeks after operation may hinder an adolescent's ability to swallow a large multivitamin pill, and even a chewable vitamin may not be as palatable postoperatively as it was preoperatively.
This is the first study to systematically examine barriers to multivitamin adherence in adolescents who have undergone bariatric surgery. The primary barrier prior to surgery was forgetting, the most commonly reported barrier across most pediatric conditions (17
). Interestingly, difficulty swallowing multivitamins became more prominent one-month after surgery. This finding could be due to changes in taste and deglutition (i.e., swallowing), as more than 80% of bariatric patients report changes in taste sensations as well as certain food aversions (23
). Dramatic changes in the production of numerous gut-derived peptides after RYGB have been documented and implicated in the alterations in gustatory pathways (24
). Such alterations could conceivably play a role in taste sensations, particularly associated with vitamins with a residual aftertaste. By six-months following surgery, forgetting resumed as the primary barrier, surpassing difficulty swallowing multivitamins. It is possible that if adolescents initially have difficulty swallowing multivitamins, they never re-initiate this behavior, leading to declines in adherence over time.
The clinical implications of reduced multivitamin adherence are significant. Even prior to surgery, many severely obese children and adults have a variety of nutritional deficiencies primarily felt to be secondary to nutrient poor diets (25
). However bariatric surgery, whether the procedure is purely restrictive or malabsorptive-restrictive, can increase the risk of both short term and long-term nutritional deficiencies. Risk factors for nutritional deficiency specific to bariatric surgery include diminished oral intake, especially in the first few months after surgery, as well as an additive risk of micronutrient maldigestion/malabsorption if a large portion of stomach or intestine is bypassed. Risk of acute nutritional deficiencies can also be worsened if significant post-operative nausea and vomiting occurs in the early-postoperative period.
Though generally mild for most patients, deficiencies of iron, vitamins B12, D and thiamine can lead to clinically significant anemia, osteopenia and neurological dysfunction in some patients (11
). Severe cases of iron deficiency anemia refractory to oral therapy may also require serial parenteral iron infusions (31
). In women of child-bearing age, it is also critically important to screen and treat nutritional deficiencies before and during pregnancies, to avoid serious complications in both mother and infant (32
). Deficiencies in fat soluble vitamins, vitamin C, zinc, selenium and copper are far less common and more likely to occur after more malabsorptive procedures such as biliopancreatic diversion, but some cases have been reported to occur even after gastric bypass (25
). Therefore, lifelong multivitamin supplementation is considered the standard of care in bariatric practice (11
), which is true of our clinical practice as well.
While the present data suggest concern, an important consideration for this patient population is the relative paucity of data to establish the absolute need, optimal dose, or dosing frequency for multivitamins following bariatric surgery. One prospective trial established the importance of iron supplementation in females after RYGB (34
); however, there are no prospective studies demonstrating the need, optimal dose, or dosing frequency for multivitamins following RYGB. Despite this fact, it is still reasonable and prudent to recommend multivitamin supplementation due to diminished intake and bypass of the duodenum following RYGB. In the context of the current study, it is possible that twice daily dosing of multivitamins is too burdensome for adolescents compared to once daily dosing of 2 multivitamin tablets, which may be equally effective for supplementation.
The clinical implications of our study findings are two-fold. First, it is clear that existing self-report measures of adherence lack the reliability necessary to make meaningful decisions about clinical care. For example, if a patient is experiencing micronutrient deficiencies, the clinician may increase a vitamin dose or change vitamin/mineral supplementation, and not consider the patient's adherence to the medication. While anecdotally, a “don't ask, don't tell” communication style regarding adherence has prevailed, we encourage clinicians to begin a dialogue with adolescents and their families regarding adherence to treatment recommendations. Use of non-judgmental language can help improve patient-provider communication and in turn, the clinical care of patients. Adolescents may be responsive to dialogue that normalizes non-adherence and encourages identification of adherence barriers, for instance: “Taking multivitamins is difficult to do every day. In fact, most patients miss medications occasionally. In the past week, how many doses of your multivitamin did you miss? What makes it difficult to take your multivitamin?” Second, if non-adherence is suspected and the barriers to non-adherence are identified, there are empirically-supported treatments to improve adherence. For example, barriers to adherence, such as forgetting, can easily be addressed through adherence-promotion interventions (35
) focused on problem-solving. For adolescents in particular, technology-based interventions, such as cell-phone text reminders or pill reminder applications on smartphones, may be beneficial and should be pilot-tested. Furthermore, there are several empirically-supported treatments to improve pill-swallowing that may be beneficial to adolescents following bariatric surgery (36
). In addition, for patients struggling with pill-swallowing, healthcare providers may suggest alternative liquid multivitamin formulations instead of pills/tablets. As no pill must be digested, liquid formulations may additionally maximize absorption in surgeries in which portions of the proximal intestinal tract are bypassed (roux-en-y gastric bypass, biliopancreatic diversion) or production of stomach acid is reduced (sleeve gastrectomy, roux-en-y gastric bypass).
Several limitations are noted that have direct implications for future research. First, electronic monitors cannot confirm ingestion of the medication and thus data are considered a proxy. In addition, patients could also remove more than one multivitamin dose for later ingestion when the bottle was opened, yielding an underestimation of adherence. Electronic monitoring data was also missing for several participants at the one and six-month follow-up visits due to loss or discontinued use of the electronic monitors. This is unfortunately an inherent issue and limitation of electronic monitoring of adherence and may be most salient for adolescent populations. Second, it is plausible that adherence behaviors may have been influenced by the monitoring itself (i.e., reactivity). However, adherence research has demonstrated that reactivity is negligent or short-lived with adherence behaviors returning to baseline shortly after monitoring is initiated (38
). Third, we utilized one ad-hoc question representing adherence in the past week instead of a well-validated self-report adherence questionnaire. While this approach is necessarily limited in scope, it does represent how clinicians ask about adherence in clinical practice. As such, our approach may be more generalizable. Fourth, our sample primarily included Caucasian females and thus results may not be generalizable. Finally, the long-term consequences of non-adherence to multivitamin therapy in adolescents who have undergone bariatric surgery remain unknown. Future studies are critically needed and ongoing within the Teen-LABS consortium, which will begin to establish vitamin and mineral requirements following various surgical procedures to inform best practice techniques to encourage optimal adherence.
The current study is the first to examine multivitamin adherence, using an empirically-supported objective measure, over a six-month period in adolescents who have undergone bariatric surgery. These high rates of non-adherence to multivitamin therapy should be taken into account when devising treatment and family education pathways for adolescents considering weight loss surgery.