Predictors of Medication Adherence in Inflammatory Bowel Disease

Jason P. Ediger, Ph.D.; John R. Walker, Ph.D.; Lesley Graff, Ph.D.; Lisa Lix, Ph.D.; Ian Clara, Ph.D.; Patricia Rawsthorne, R.N.; Linda Rogala, R.N.; Norine Miller, R.N.; Cory McPhail, B.A.; Kathleen Deering, B.A.; Charles N. Bernstein, M.D.

Disclosures

Am J Gastroenterol. 2007;102(7):1417-1426. 

In This Article

Abstract and Introduction

Abstract

Background and Aims: This study reports cross-sectional medication adherence data from year 1 of the Manitoba Inflammatory Bowel Disease (IBD) Cohort Study, a longitudinal, population-based study of multiple determinants of health outcomes in IBD in those diagnosed within 7 yr.
Methods: A total of 326 participants completed a validated multi-item self-report measure of adherence, which assesses a range of adherence behaviors. Demographic, clinical, and psycho-social characteristics were also assessed by survey. Adherence was initially considered as a continuous variable and then categorized as high or low adherence for logistic regression analysis to determine predictors of adherence behavior.
Results: Using the cutoff score of 20/25 on the Medication Adherence Report Scale, high adherence was reported by 73% of men and 63% of women. For men, predictors of low adherence included diagnosis (UC: OR 4.42, 95% CI 1.66-11.75) and employment status (employed: OR 11.27, 95% CI 2.05-62.08). For women, predictors of low adherence included younger age (under 30 versus over 50 OR 3.64, 95% CI 1.41-9.43; under 30 vs. 40-49 yr: OR 2.62, 95% CI 1.07-6.42). High scores on the Obstacles to Medication Use Scale strongly related to low adherence for both men (OR 4.05, 95% CI 1.40-11.70) and women (OR 3.89, 95% CI 1.90-7.99). 5-ASA use (oral or rectal) was not related to adherence. For women, immunosuppressant use versus no use was associated with high adherence (OR 4.49, 95% CI 1.58-12.76). Low trait agreeableness was associated with low adherence (OR 2.03, 95% CI 1.12-3.66).
Conclusions: Approximately one-third of IBD patients were low adherers. Predictors of adherence differed markedly between genders, although obstacles such as medication cost were relevant for both men and women.

Introduction

Medication represents a cornerstone of modern treatment strategies for inflammatory bowel disease (IBD). Appropriate use can help patients to induce remission and maintain those gains over time.[1,2,3,4] Nevertheless, the medication can be costly and difficult to take with unpleasant side effects, all of which may result in less than optimal adherence to the treatment regimen and poorer outcomes for disease management. In this context, treatment adherence has significant implications for patient well-being and treatment outcome. Given that physicians typically have limited control over this facet of treatment, adherence also represents the greatest point of vulnerability in this intervention. This is particularly salient in the treatment of chronic disease when patients may be asked to adhere to a specific regimen for several years at a time. Poor medication adherence has been well established in this context when assessing hypertension and diabetes with rates varying between 50% and 65%.[5,6] Hence, it is important to identify factors related to poor treatment adherence in IBD.

IBD has previously been identified as a particularly high-risk illness for poor adherence.[7,8] Individuals are often diagnosed relatively young and must cope with the disease for many years. Treatments can be inconvenient and difficult to follow. Furthermore, the disease has an unpredictable course with potentially long periods of inactivity. IBD patients must have a strong belief in their doctor's plan and strong convictions about the necessity of the treatment to optimally follow through with the treatment plan.[8] Nonadherence rates for short-term therapy have been described as varying from 20% to 40% and rise as high as 72% for longer-term therapies.[8,9,10]

Low medication adherence for those with IBD has been linked to male gender, younger age, a higher number of prescribed medications, high disease activity, shorter disease duration, and psychiatric comorbidity.[9,10,11] Other research has highlighted the importance of doctor-patient relationships, frequency of medical appointments, and beliefs about medication in predicting medication adherence.[8] Replication of these predictors across studies has been inconsistent, however. As such, there is currently no well-validated profile for IBD patients with low medication adherence. Many of the studies done to date have been hampered by a variety of methodological limitations including small and potentially unrepresentative samples.

It has been challenging to develop valid and inexpensive measures of adherence. Determination of high and low adherence often differs based on methodology and the types of medication under examination. Adherence has been measured in a variety of different ways including pill counts, pharmacy data, assays of blood or urine, electronic medication dispensers, and verbal reports of compliance.[12] The more objective methods of adherence have most often been used in treatment studies where patients have frequent monitoring and contact with treatment staff. This frequent monitoring (designed to improve adherence) is clearly not characteristic of usual treatment and can result in adherence behavior that is not typical. In situations where patients are receiving diverse forms of treatment and have less frequent contact from treatment staff, verbal report has been used most often because it is less costly and allows assessment of a more diverse range of treatment recommendations. However, the degree of agreement among these various forms of assessment for treatment adherence can vary.

Standardized self-report approaches have proven to be an efficient and effective method of determining medication adherence.[12] They have established validity, positively correlating with pill counts,[13] blood pressure control,[14] and virological outcome.[15] However, self-report on treatment adherence has been most often assessed using very brief measures, and a limited scale of responses (yes/no). Commonly used measures, such as the Moriskey,[16] can lead to a fairly arbitrary definition of adherence that is often dependent on the answer to a single question.

An obstacle inherent in adherence research is obtaining data that are representative of the broad spectrum of the patient population regarding their adherence behavior. That is, studies typically rely on patient samples seeking treatment in specialty clinics.[7,8,17] These data, while important, may reflect a sampling bias by assessing patients in specialized follow-up settings. Patients may be more likely to have active disease and/or more positive beliefs about the medical system under these circumstances. Our aim was to study factors related to treatment adherence in a population-based community sample of those with IBD that includes patients across the spectrum of disease activity.

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