Adherence to diabetes medication: a systematic review

Aims: To investigate the extent of and factors associated with adherence to Type 2 diabetes medication.

Methods: The CINAHL, Embase, International Pharmaceutical Abstracts, Medline, PubMed and PsychINFO databases were searched for the period January 2004 to July 2013. Papers were included in the present review if they reported the prevalence of adherence (the percentage of the study population that is classified as adherent) to Type 2 diabetes medication and used validated adherence measures with a defined cut-off point to indicate adherence. Reported factors were classified as potential predictors if the studies that examined that particular variable reported consistent findings.

Results: Of the 27 studies included in the present review, the prevalence of adherence ranged from 38.5 to 93.1%. Only six out of 27 studies (22.2%) reported prevalence of adherence of ≥ 80% among their study population. Depression and medication cost were found to be consistent and potentially modifiable predictors for diabetes medication-taking behaviour. The associations between adherence and other factors were inconsistent among the reviewed studies.

Conclusions: Adherence to diabetes medication remains an ongoing problem. This review has highlighted the urgent need to develop consensus about what constitutes good adherence in diabetes. Further research is needed to clarify modifiable factors, in addition to depression and medication cost, that influence adherence and may provide a focus for targeted interventions to promote adherence, optimize diabetes control and limit the progression of diabetes.