Costs of Medication Nonadherence in Patients with Diabetes Mellitus: A Systematic Review and Critical Analysis of the Literature

Abstract

Important variation among cost estimates was evident, even within studies of the same population. Readers should be cautious when comparing estimated coefficients from various studies because methodological issues might explain differences in the results of costs of nonadherence in diabetes. This is particularly important when estimates are used as inputs to pharmacoeconomic models.

Descriptive Analysis of Mail Interventions with Physicians and Patients to Improve Adherence with Antihypertensive and Antidiabetic Medications in a Mixed-Model Managed Care Organization of Commercial and Medicare Members

“…7 Most studies of nonadherence use medication possession ratios (MPR), but other measures of adherence include proportion of days covered or the proportion of doses taken as prescribed. [5][6][7] Investigators have found that improving medication adherence is associated with decreases in adverse drug events, hospitalizations, health care What is already known about this subject (continued)…”

“…2 Studies have shown that rates of refilling prescriptions are an accurate measure of overall adherence in a closed pharmacy system, provided that refills are measured at several points in time. [3][4][5] Medication nonadherence is a recognized public health concern, and nonadherence rates vary considerably among studies. For example, nonadherence for diabetic patients receiving oral antidiabetic agents ranged from 36% to 93% in 1 systematic review by Cramer (2004).…”

Still Looking for Health Outcomes in All the Wrong Places? Misinterpreted Observational Evidence, Medication Adherence Promotion, and Value-Based Insurance Design

“…19 Instead of studying the expected physiological outcomes of statin therapy, such as reduced rates of myocardial infarction or lower cardiovascular expenditures, Dormuth et al assessed outcomes that are physiologically highly unlikely to be related to statin use. After statistically adjusting for confounders in a Cox regression analysis, using a method similar in approach to those used in other adherence studies, [20][21][22][23][24][25][26]30,34,35 Dormuth et al found that statin-adherent patients were less likely than nonadherent patients to have motor vehicle accidents (HR = 0.75, 95% CI = 0.72-0.79) or workplace accidents (HR = 0.77, 95% CI = 0.74-0.81) or to develop diseases unlikely to be related to the biological effects of a statin (HR = 0.87, 95% CI = 0.86-0.89). Statin-adherent patients were also more likely than nonadherent patients to use preventive screening services (HR = 1.17, 95% CI = 1.15-1.20).…”

“…[14][15][16][17][18] 19 Such studies of associations between medication adherence and various outcomes-including mortality, hospitalization, and health care expenditures-have become familiar fare to managed care decision makers. [20][21][22][23][24][25][26] Typically consisting of retrospective analyses of administrative claims data, almost always with statistical adjustments for measured confounders, these studies routinely find that higher rates of medication adherence are associated with better outcomes and lower disease-related or all-cause health care cost. [20][21][22][23][24][25][26] These associations between adherence and improved health outcomes are often cited in assessments of various treatments that increase pharmacy benefit spending, such as newer products with less frequent dosing 22,27 or fixed-dose single-pill combinations containing drugs available individually as generic drugs.…”

“…[20][21][22][23][24][25][26] Typically consisting of retrospective analyses of administrative claims data, almost always with statistical adjustments for measured confounders, these studies routinely find that higher rates of medication adherence are associated with better outcomes and lower disease-related or all-cause health care cost. [20][21][22][23][24][25][26] These associations between adherence and improved health outcomes are often cited in assessments of various treatments that increase pharmacy benefit spending, such as newer products with less frequent dosing 22,27 or fixed-dose single-pill combinations containing drugs available individually as generic drugs. 20,21,28 The objective of this type of assessment is, of course, to suggest that if the payer is willing to adopt the new product, the increased prescription drug expense potentially could be partly or fully offset by reductions in total medical cost.…”