The cost and effectiveness of adherence-improving interventions for antihypertensive and lipid-lowering drugs

Aims: Adherence to cardiovascular medications is poor. Accordingly, interventions have been proposed to improve adherence. However, as intervention-associated costs are rarely considered in full, we sought to review the effectiveness and costs associated with different adherence-improving interventions for cardiovascular disease therapies. Methods: We reviewed MEDLINE to update a prior review of interventions to improve adherence with antihypertensive and/or lipid-lowering therapy covering January 1972 to June 2002, to add studies published from July 2002 to October 2007. Eligible studies evaluated 1 intervention compared with a control, used measures other than self-report, reported significant improvement in adherence and followed patients for 6 months. Effectiveness was measured as relative improvement (RI), the ratio of adherence in the intervention group to the control group. Costs were calculated based on those reported in the analysis, if available or estimated based on resource use described. All costs were truncated to 6 months and adjusted to 2007 US$. Results: Of 755 new articles, five met all eligibility criteria. Combining with the prior review gave 23 interventions from 18 studies. RI in adherence ranged from 1.11 to 4.65. Six-month intervention costs ranged from $10 to $142 per patient. Reminders had the lowest effectiveness (RI: 1.11-1.14), but were least costly ($10/6 months). Case management was most effective (RI: 1.23-4.65), but the most costly ($90-$130/6 months). Conclusions: Generally, we found a positive association between intervention costs and effectiveness. Therefore, consideration of intervention costs, along with the benefits afforded to adherence, may help guide the design and implementation of adherence-improving programs.