Prevalence and economic consequences of medication adherence in diabetes: a systematic literature review.

A systematic literature review was conducted using a comprehensive list of relevant search terms (1990-2005) to identify studies on adherence among patients with diabetes, and its economic effect. A lack of adequate treatment adherence (36%-87%) among patients with diabetes was confirmed, primarily measured by medication possession ratio (MPR). Adherence varied among oral agent-only (36%-87%) versus concomitant or insulin-only (54%-81%) regimens. Economic consequences of adherence were a decrease in health care costs, ranging from 8.6% to 28.9%, with an approximate 10% increase in MPR, mostly in the form of a 4.1% to 31.0% decrease in hospitalization. Increased cost sharing was associated with a 9% to 23% decline in medication use.