Institute of General Practice and Health Services Research, TUM School of Medicine, Technical University of Munich, Orleansstraße 47, 81667, Munich, Germany.
Vilua Healthcare GmbH, Berlin, Germany.
Appl Health Econ Health Policy. 2023 May;21(3):477-487. doi: 10.1007/s40258-023-00797-6. Epub 2023 Mar 18.
Despite the importance of medication adherence for chronically ill patients and the vast literature on its relationship to costs, this field suffers from methodological limitations. These are caused, amongst others, by the lack of generalizability of data sources, varying definitions of adherence, costs, and model specification. We aim to address this with different modeling approaches and to contribute evidence on the research question.
We extracted large cohorts of nine chronic diseases (n = 6747-402,898) from German claims data of stationary health insurances between 2012 and 2015 (t0-t3). Defined as the proportion of days covered by medication, we examined the relationship of adherence using several multiple regression models at baseline year t0 with annual total healthcare costs and four sub-categories. Models with concurrent, and differently time-lagged measurements of adherence and costs were compared. Exploratively, we applied non-linear models.
Overall, we found a positive association between the proportion of days covered by medication and total costs, a weak association with outpatient costs, positive with pharmacy costs, and frequently negative with inpatient costs. There were major differences by disease and its severity but little between years, provided adherence and costs were not measured concurrently. The fit of linear models was mainly not inferior to that of non-linear models.
The estimated effect on total costs differed from most other studies, which highlights concerns about generalizability, although effect estimates in sub-categories were as expected. Comparison of time lags indicates the importance of avoiding concurrent measurement. A non-linear relationship should be considered. These methodological approaches are valuable in future research on adherence and its consequences.
尽管药物依从性对慢性病患者至关重要，并且有大量关于其与成本关系的文献，但该领域存在方法学限制。这些限制是由数据来源的普遍性不足、依从性、成本和模型规范的定义不同等原因造成的。我们旨在通过不同的建模方法来解决这些问题，并为研究问题提供证据。
我们从 2012 年至 2015 年（t0-t3）德国固定健康保险的索赔数据中提取了九种慢性病的大型队列（n=6747-402898）。我们使用几种多元回归模型，在基线年 t0 时根据药物覆盖率的比例来检查依从性与年度总医疗成本和四个子类别之间的关系。比较了同时和不同时间滞后测量依从性和成本的模型。探索性地，我们应用了非线性模型。
总体而言，我们发现药物覆盖率与总费用之间存在正相关，与门诊费用之间存在弱相关，与药房费用之间存在正相关，与住院费用之间经常存在负相关。疾病及其严重程度之间存在重大差异，但如果不同时测量依从性和成本，则年份之间差异很小。线性模型的拟合度主要不劣于非线性模型。
对总费用的估计影响与大多数其他研究不同，这突出了对普遍性的关注，尽管子类别中的效应估计是预期的。时间滞后的比较表明避免同时测量的重要性。应考虑非线性关系。这些方法在未来的依从性及其后果研究中具有价值。
