Our review of interventions to improve adherence to cardiovascular and diabetes medications yielded a highly diverse group of interventions. Several themes arose regarding the effectiveness of different approaches that may inform future intervention development.
Among person-independent interventions, those that used electronic interventions showed promise. Effective electronic interventions included those that were designed to be individualized using either computer-generated algorithms or hierarchically structured messages, and one study effectively combined hierarchical phone messages and targeted phone follow-up by a nurse. Home automatic blood pressure monitoring and programmable pill caps with reminder cues also demonstrated promising results. Adherence interventions delivered via paper or video showed minimal effectiveness unless targeted at a group (in this case hospitalized patients post-myocardial infarct) that was especially likely to be sensitive to the message.
Among person-dependent interventions, the results of phone call interventions were not encouraging. Only a minority were effective. These interventions targeted groups at a time in their lives when they should have been particularly sensitive to the message (e.g., immediately post bypass surgery, percutaneous intervention or hospitalization for congestive heart failure, or after a new diagnosis of hypertension).
In-person interventions yielded some interesting patterns. Home visits, an expensive intervention, were only effective in half the studies identified; both of the effective studies sought to target a family member as support person, while neither of the ineffective studies did so. The data on worksite interventions were limited and no recent studies were identified. Interventions carried out in the pharmacy (all by pharmacists) were almost uniformly effective and were a fairly homogenous group in both the nature of the services rendered and in duration of follow-up. Interestingly, when we looked at the group of interventions carried out in the clinic by pharmacists, only three out of eight were effective. All three of these were carried out in clinics that also had dispensing abilities and therefore may have been more similar to the group of in-person pharmacy interventions. Interventions that targeted patients at the point of hospital discharge were more effective than those that focused on clinic patients, though the lower number of in-person hospital studies should be noted (6 compared to 15 clinic studies).
Person-dependent administration of an adherence intervention can be costly, whether carried out by a lay person, nurse, pharmacist or physician. We found the success rate of person-dependent interventions comparable or lower than that of person-independent interventions. We interpret this result cautiously, given the presence of fewer person-independent interventions overall.
The wide heterogeneity of the adherence intervention studies we identified should prompt us to interpret all comparisons with caution. We included studies with differing populations (patients from different countries and with different cardiovascular diseases; nonadherent vs. all patients; hospitalized vs. outpatient) and we encountered a wide variety of study designs, including some with idiosyncracies that limited their generalizability. In addition, while a detailed discussion of comparative adherence measurement methods is outside the scope of this paper, we found inconsistencies in methods of adherence measurement across the studies reviewed, demonstrated most clearly in our tables. Direct comparison of the magnitude of intervention effect is complicated by this heterogeneity. While we were able to consider some aspects of healthcare setting in our analysis, stratification by health care facility size was not possible due to inconsistencies in reporting. Finally, although over 40% of studies identified showed no significant improvement, publication bias may also be playing a role in our findings.
We suggest that future research focus on (1) the life-events causing increased patient receptiveness to the adherence message (i.e. hospital stays, particularly after a serious cardiac event); (2) the psychological factors present during an acute illness and hospital stay as they relate to a patient’s willingness to modify adherence behavior; (3) in-person pharmacist counsel delivered at the site of medication dispensing (so that arriving for an appointment to discuss adherence can be combined with retrieving the medication); (4) new and innovative ways to take advantage of electronic technologies.
We saw few interventions that capitalized on lay-person social networks, either electronic or in-person. Research on adherence to other medically recommended behaviors including cancer screening has indicated that this may be a promising direction57
, and the same may be true for medication adherence interventions.
In conclusion, among interventions to improve adherence to cardiovascular medications, electronic interventions, in-person pharmacist interventions held at a site of medication dispensing, and in-person interventions targeted to patients at the point of hospital discharge showed the highest rates of success. Future studies should explore new electronic approaches and in-person interventions at the site of medication distribution. A focus on identifying times of increased patient receptivity to the adherence message will also be important.