Intentional and unintentional non-adherence in community dwelling people with type 2 diabetes: the effect of varying numbers of medicines

People with type 2 diabetes are often prescribed multi-medicines which can be difficult to manage. Non-adherence to medicines can be intentional (e.g. active decision) or unintentional (e.g. forgetting). The objective of this study was to measure intentional and unintentional non-adherence to differing numbers of medicines prescribed in type 2 diabetes. A cross-sectional survey using the Morisky medication adherence scale (with intentional and unintentional non-adherence subscales) was completed by 480 people prescribed oral antidiabetic drugs (OADs), antihypertensive agents and statins. A within-subject analysis of variance (ANOVA) showed that intentional non-adherence did not vary between OADs, anti-hypertensives and statins. Intentional non-adherence to statins significantly increased when the number of medicines prescribed was included as a between-subjects variable (p<0.05). Another within-subject ANOVA on unintentional non-adherence found a significant difference between OADs, anti-hypertensives and statins; unintentional non-adherence to OADs was significantly higher (p<0.05). When the number of medicines was added as a between-subject variable unintentional non-adherence was associated with higher numbers of medicines. This study shows the difference between intentional and unintentional non-adherence behaviours, and the effect that varying numbers of medicines can have on these behaviours.