Medication Adherence and Healthcare Costs in Chronically Ill Patients Using German Claims Data

Area of Science:

• Health economics
• Pharmacoeconomics
• Chronic disease management

Background:

• Medication adherence is critical for chronically ill patients, yet research is limited by methodological issues like data generalizability and inconsistent definitions.
• Existing studies on medication adherence and healthcare costs face challenges in data sources, adherence/cost definitions, and model specification.

Purpose of the Study:

• To address methodological limitations in studying medication adherence and healthcare costs using diverse modeling approaches.
• To investigate the relationship between medication adherence (proportion of days covered) and total healthcare costs, including outpatient, pharmacy, and inpatient costs, across nine chronic diseases.

Main Methods:

• Analysis of large German health insurance claims data (2012-2015) for nine chronic diseases.
• Utilized multiple regression models to assess adherence's association with annual costs, comparing concurrent and time-lagged measurements.
• Exploratively applied non-linear models to examine adherence-cost relationships.

Main Results:

• A positive association was observed between medication adherence and total healthcare costs, with variations across cost sub-categories (weak for outpatient, positive for pharmacy, negative for inpatient).
• Significant differences in associations were noted by disease and severity, with minimal year-to-year variation when adherence and costs were not concurrently measured.
• Linear models generally performed comparably to non-linear models in terms of fit.

Conclusions:

• Findings on total costs differ from previous studies, emphasizing generalizability concerns, though sub-category estimates align with expectations.
• Concurrent measurement of adherence and costs should be avoided; non-linear relationships warrant consideration in future research.
• The employed methodological approaches offer valuable insights for future studies on medication adherence and its economic consequences.