Adherence to antidiabetic (AD) medication is a multifactorial phenomenon; however, little is known about which factors are the most contributory. Our objective was to conduct a systematic review aiming to quantify the effect of factors associated with medication nonadherence in patients with type 2 diabetes using non-insulin AD (NIAD) drugs. We conducted a systematic literature search of relevant observational studies published from January 1997 through March 2017. Studies were included if they used medication possession ratio (MPR) or proportion of days covered (PDC) to evaluate adherence associated with factors, were published in the last 10 years, and did not include insulin. The factors identified were then grouped based on the dimensions of medication adherence defined by the World Health Organization (WHO). The search yielded 1studies of which 25 met criteria. Socioeconomic factors associated with increased adherence were older age, male gender, and Caucasian race which were supported by 15, 10, and 8 studies, respectively. Health system related-factors associated with increased adherence were a general practitioner as the initial prescriber and mailed prescriptions, which were supported by 2 and 3 studies, respectively. The most prevalent condition-related factors were no hospitalized in the past year, frequent physician visits, and absence of cancer, each of which were supported by 3 studies. In regards to therapy-related factors, patients prescribed metformin, and who have a higher pill burden are more likely to be adherent, which were supported by 5 and 8 studies respectively. Only one study analyzed a WHO defined patient-related factor, which found a negative relationship between patients’ diabetes-related knowledge and adherence.

In conclusion, the major factors reported to be associated with NIAD nonadherence were younger age, female, non-Caucasian race, not using mailed prescriptions, cancer diagnosis, lower number of comorbidities, and a smaller pill burden.


L. Petrenchik: None. F. Loh: None.

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