PHILADELPHIA -- High prescription drug co-payments are associated with lower medication adherence and higher total healthcare costs, according to a new study published this month in the Journal of Occupational and Environmental Medicine.

The study, funded by GlaxoSmithKline, investigated the effects of varied co-payment levels on oral diabetes medication adherence, health resource utilization, and total health costs for PPG Industries employees, retirees, and dependents.

In comparing medication adherence and healthcare costs for patients with diabetes, PPG Industries, a global manufacturer and provider of coatings, glass and chemical products, noted that those with lower co-payments had better adherence to oral diabetes medicines, and averaged $3116 less per year in total health care costs than those in the highest co-payment group.

Poor medication adherence can be attributed to several factors. The effects of high prescription drug co-payments have been studied extensively since they have often been used by employers and insurers in an attempt to contain spiraling drug costs for chronic diseases, such as diabetes, and to prevent individuals from seeking unnecessary medical care. Increasing co-payments has been shown to decrease use of medications for chronic conditions. Until recently, few studies have investigated the relationship between co-payment level, adherence, and use of subsequent health resources.

The Effects of Health Plan Co-payments on Adherence to Oral Diabetes Medication and Health Resources Utilization was a 2-year retrospective study. In it, PPG Industries analyzed the eligibility, medical, and pharmacy claims data from 2052 employees, retirees, and dependents with type 2 diabetes to determine the impact of different co-payment levels.