Association between drug insurance cost sharing strategies and outcomes in patients with chronic diseases: a systematic review

PLoS One. 2014 Mar 25;9(3):e89168. doi: 10.1371/journal.pone.0089168. eCollection 2014.


Background: Prescription drugs are used in people with hypertension, diabetes, and cardiovascular disease to manage their illness. Patient cost sharing strategies such as copayments and deductibles are often employed to lower expenditures for prescription drug insurance plans, but the impact on health outcomes in these patients is unclear.

Objective: To determine the association between drug insurance and patient cost sharing strategies on medication adherence, clinical and economic outcomes in those with chronic diseases (defined herein as diabetes, hypertension, hypercholesterolemia, coronary artery disease, and cerebrovascular disease).

Methods: Studies were included if they examined various cost sharing strategies including copayments, coinsurance, fixed copayments, deductibles and maximum out-of-pocket expenditures. Value-based insurance design and reference based pricing studies were excluded. Two reviewers independently identified original intervention studies (randomized controlled trials, interrupted time series, and controlled before-after designs). MEDLINE, EMBASE, Cochrane Library, CINAHL, and relevant reference lists were searched until March 2013. Two reviewers independently assessed studies for inclusion, quality, and extracted data. Eleven studies, assessing the impact of seven policy changes, were included: 2 separate reports of one randomized controlled trial, 4 interrupted time series, and 5 controlled before-after studies.

Findings: Outcomes included medication adherence, clinical events (myocardial infarction, stroke, death), quality of life, healthcare utilization, or cost. The heterogeneity among the studies precluded meta-analysis. Few studies reported the impact of cost sharing strategies on mortality, clinical and economic outcomes. The association between patient copayments and medication adherence varied across studies, ranging from no difference to significantly lower adherence, depending on the amount of the copayment.

Conclusion: Lowering cost sharing in patients with chronic diseases may improve adherence, but the impact on clinical and economic outcomes is uncertain.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review
  • Systematic Review

MeSH terms

  • Chronic Disease / drug therapy
  • Chronic Disease / economics*
  • Cost Sharing*
  • Health Expenditures / trends*
  • Humans
  • Insurance, Pharmaceutical Services*
  • Medication Adherence*
  • Outcome Assessment, Health Care*
  • Quality of Life

Grant support

Dr. Campbell is supported by an Alberta Innovates - Health Solutions (AI-HS) Clinician Fellowship award. Dr. Barnieh is supported by an Alberta Innovates - Health Solutions Trainee award. Drs. Manns and Hemmelgarn are supported by career salary support awards from Alberta Innovates - Health Solutions. Dr. Hemmelgarn is also supported by the Roy and Vi Baay Chair in Kidney Research. Dr. Tonelli is supported by a Government of Canada Research Chair. Drs. Manns, Hemmelgarn, and Tonelli are also supported by an alternative funding plan from the Government of Alberta and the Universities of Calgary and Alberta. Primary Funding Source: This study was funded by a team grant from Alberta Innovates – Health Solutions to the Interdisciplinary Chronic Disease Collaboration. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.