Effects of using a text message intervention on psychological constructs and the association between changes to psychological constructs and medication adherence in people with type 2 diabetes: Results from a randomised controlled feasibility study

Background:
Poor adherence to oral medications is common in people with type 2 diabetes and can lead to an increased chance of health complications. Text messages may provide an effective delivery method for an intervention, however thus far, the majority of these interventions do not specify either a theoretical basis or propose specific mechanisms of action. This makes it hard to determine how an intervention is having an effect, or not. The text messages included in this intervention have been developed to deliver specific behaviour change techniques. These techniques are the ‘active ingredients’ of the intervention and were selected to target psychological constructs identified as predictors of medication adherence.

Objective:
(1) to assess whether a text message intervention with specified behaviour change techniques can change constructs that predict medication adherence behaviours in people with type 2 diabetes, and (2) to assess whether changes to psychological constructs are associated with changes in medication adherence.

Methods:
A randomised controlled 6-month feasibility trial. Adults prescribed oral medication for type 2 diabetes (n=209) were recruited from general practice and randomised to either receive a text message-based intervention or care as usual. Data were analysed with repeated measures ANCOVA and Spearman’s Rho correlation coefficients.

Results:
For eight of the 14 constructs that were measured a significant time by condition interaction was found: necessity beliefs, intention, maintenance self-efficacy, recovery self-efficacy, action control, prompts and cues, social support and satisfaction with experienced consequences all increased in the intervention group compared to the control group. Changes in action self-efficacy, intention, automaticity, maintenance self-efficacy and satisfaction with experienced consequences were positively associated with changes in medication adherence.

Conclusions:
A relatively low-cost, scalable text message-only intervention targeting medication adherence using behaviour change techniques can influence psychological constructs that predict adherence. These constructs not only predict medication adherence, but changes in these constructs are correlated with changes in medication adherence. These findings support the promise of text message-based interventions for medication adherence in this population and suggest likely mechanisms of action. Clinical Trial: ISRCTN13404264