Diabetes is a major public health problem. The number of people with diabetes is estimated to reach 330 million by 2030 [1
]. There is a high clinical and economic burden from the disease [2
]: people with diabetes have a two-to-four fold increased risk of cardiovascular disease compared to the general population and increased incidence of retinopathy, peripheral nerve damage and renal problems.
Evidence supports the use of multiple medications to control blood glucose and cardiovascular risk among patients with type 2 diabetes [3
], and, this may lead to prescriptions of eight or more medications a day. Up to half of this medication may not be taken as prescribed [4
], with adherence to medication falling as dosage frequency rises [6
]. Failure to take medication has important consequences. It not only reduces efficacy of the treatment, but wastes healthcare resources in prescribed pills not taken, extra consultations, referrals, investigations and hospital admissions [7
]. The availability of an effective intervention to support patients with type 2 diabetes in taking their medication regularly would make a major contribution to human health.
A variety of interventions to support adherence to medication have been tested for efficacy [9
], and their clinical application assessed [10
]. Although some interventions are effective in improving adherence, the results are inconsistent. These studies have used complex packages of care, targeting multiple self-care activities and therefore limiting identification of factors that lead to and might modify non-adherence. Approaches to supporting behaviour change are now informed by evidence about the psychological determinants of behaviour, and techniques to alter them, and there is potential to apply these techniques in the field of medication adherence [11
Adherence to medication can be defined in many ways. Our definition is the extent to which medicines are taken regularly as prescribed. We argue that to understand the determinants of adherence better and optimise the impact of different intervention components upon them, we need to design interventions based on clear conceptual frameworks. We also need to test whether targeting determinants of medication adherence (e.g., patient's beliefs) results in greater levels of adherence [11
People may not take their medication because of ambivalence about pros and cons of adherence (intentional lapse). Others, who intend to take their medications regularly, may still forget to do so (non-intentional lapse). Intentional and non-intentional lapses in adherence have been identified as two important elements contributing to overall non-adherence [14
]. Drawing on psychological theory and evidence [15
], we have developed approaches to address these two elements: to increase patients' motivation to take their tablets regularly by targeting underlying beliefs; and to help patients define specific action plans to facilitate the translation of intentions into action and habit formation. The two components can be defined as motivational – targeting the cognitive determinants of intention – and volitional – defining action plans to implement the target behaviour [15
The motivational component of the intervention is based on the Theory of Planned Behaviour (TPB) [16
]. This theory specifies beliefs which may be targeted to strengthen intention. In particular techniques include reinforcement of positive beliefs and problem solving approaches to negative beliefs. The theory's constructs account for 35 to 50% of variance in intention and 26 to 35% of variance in behaviour [17
]. This illustrates a gap between intention and behaviour. The use of action planning, also called implementation intentions[15
], is a promising approach to bridge this gap. A range of studies has demonstrated that explicit consideration of the circumstances under which a behaviour will be enacted (action plans), promotes clinically important change in specific health related behaviours including consumption of vitamin C tablets, attendance for cervical cytology screening and breast self-examination [18
In clinical trials evaluating medication taking, adherence in the control group is often high. This may be because patients willing to participate in trials are likely to be adherent, because self-report measures may overestimate true adherence, or because more objective measurement focuses attention, on this target behaviour [7
]. To interpret the effects of interventions better, future trials need to characterise the population from which participants have been recruited by collecting data about non-responders, encouraging respondents who do not wish to take part in the trial to complete baseline questionnaires, and investigating the effect of measurement itself on adherence and clinical risk.
In previous pilot work we have developed measures and interventions [19
] using the approach defined by the Medical Research Council Framework for development of interventions for evaluation in randomised trials [20
]. We therefore intend to estimate the efficacy of support for medication adherence on medication taking behaviour using motivational and action planning techniques; and estimate the effect of monitoring medication-taking itself on self-reported adherence and glycaemic control in a randomised trial. The trial addresses important limitations in the literature by recruitment from a well-characterised population, definition of a feasible intervention to support medication taking, and careful measurement to estimate and interpret efficacy.