Does Medication Adherence Lead to Lower Healthcare Expenses for Patients With Diabetes? | Page 4
Published Online: August 13, 2013
Shou-Hsia Cheng, PhD; Chi-Chen Chen, PhD; and Chin-Hsiao Tseng, MD, PhD
Sensitivity Analyses. First, while using the definitions made by Sokol et al (2005)12 and Bethel et al (2007)1, we found the results were similar to those obtained by using the definition of Lau and Nau (2004)18 (eAppendix A Table 1-1 and Table 1-2). Second, while using various cut-off points for MPR (70% and 90% respectively), we found stable results concerning the association between MPR and healthcare outcomes and expenses (eAppendix B Table 2-1 and Table 2-2). Finally, the PSM process yielded a new study sample with similar distribution of the characteristics between the adherent and nonadherent groups, and generated estimates similar to the original regression models (eAppendix C Table 3-1 and Table 3-3). In summary, these sensitivity analyses indicated that the results from the study were robust.
The objectives of this study were to examine the association between medication adherence and healthcare outcomes and expenses using a longitudinal study design. The results indicated that better medication adherence was associated with decreased hospitalizations and ED visits for diabetes or cardiovascular/cerebrovascular-related conditions. We also found that medication adherence was negatively associated with healthcare expenses that were due to diabetes or cardiovascular/cerebrovascular-related hospitalizations and ED visits, but it was positively associated with the patient’s total healthcare expenses. Nevertheless, the adherence-related differences in total healthcare expenses were observed to decrease beginning 5 years after the onset of diabetes.
Our findings support previous studies suggesting that there is a significant association between medication adherence and decreased hospitalizations11,12,18-20,23 and ED visits.11 Medication adherence may lead to better glycemic control,9 which further reduces the need for hospitalizations and ED visits by decreasing the incidences of microvascular and macrovascular complications. Moreover, we found that the relationship between better medication adherence and decreased hospitalizations was stronger a certain number of years after the onset of diabetes. Given the chronic nature of diabetes, the duration of diabetes has been an increased risk of the development of complications, such as microalbuminuria36 and cardiovascular events.37 A longer follow-up study is needed to further explore the relationship between medication adherence and the occurrence of complications.
Consistent with most previous studies, we found that higher medication adherence was associated with increased drug expenses11-13 but was also associated with lower diabetes-related hospitalization or ED visit expenses.11-13 Studies regarding the effects of adherence to oral antihyperglycemic medications on total healthcare expenses are limited, and the results tend to be inconclusive.10,14 Some studies have found that increased medication adherence is associated with lower total healthcare expenses,12,21-23 while others have found the opposite relationship.11,20 Our study found that better medication adherence was associated with increased total healthcare expenses. This result implies that reduced expenses for diabetes-related hospitalizations and ED visits did not offset the higher expenses associated with oral antihyperglycemic medications or physician visits. A potential explanation for this is that because of the high accessibility to healthcare, the low cost-sharing for patients, and the fee-for-service reimbursement for physicians in Taiwan, patients are typically prescribed medications for fewer days than they need and thus are required to make a return visit to the physician. The higher expenses associated with physician visits significantly contributed to the increased total expenses for patients who had better medication adherence. However, the positive relantionship between medication adherence and total healthcare expenses was attenuated after 5 years following the onset of diabetes. Therefore, the effects of medication adherence may be more pronounced with longer duration of diabetes. A longer follow-up study and further exploration are needed.
Previous studies in the United States have found that a higher level of prescription drug cost-sharing was associated with lower medication adherence.24,25 In the present study, the mean value of MPR for patients with newly diagnosed diabetes ranged from 75.21 to 88.87% throughout the study period. An MPR of 80% is frequently considered to indicate good adherence for patients.38 The mean value of MPR in Taiwan was higher than that in some studies conducted in other countries, such as the United States9 and Korea.23 This difference may be due to Taiwan’s universal health insurance, which provides comprehensive medication coverage and involves a low drug cost-sharing requirement. However, we found that variation in MPR values still exists in a setting with low drug costsharing, which is similar to VBID in the United States. We suggest that non-financial barriers to medication adherence might also be important for improving medication adherence for patients with diabetes. Increasing the patients’ health literacy (such as their awareness of the importance of adherence), enhancing the continuity of care between physicians and patients, and the development of a pay-for-performance program to promote medication adherence are some strategies for healthcare policy makers to consider.
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