Medication utilization and adherence in a health savings account-eligible plan

To evaluate the impact of a consumerdirected health plan with a health savings account (CDHP-HSA) on utilization of and adherence to medications among individuals with chronic disease.

Pre-post comparison study with matched control group (difference-in-differences analysis).

Data on workers and dependents with 1 or more of 5 chronic conditions--hypertension, dyslipidemia, diabetes, asthma/chronic obstructive pulmonary disease (COPD), and depression--were obtained from an employer that fully replaced its preferred provider organizations (PPOs) with a CDHP-HSA in 2007. A control group of participants from an employer that maintained its PPO throughout the 3-year study period (2006-2008) was created by matching on preperiod (2006) individual characteristics. Difference-in-differences estimates of the impact of the CDHP-HSA were derived by chronic condition for number of prescriptions, proportion of days covered (PDC), and an indicator for a PDC of 0.80 or higher.

During the first year after implementation, enrollees with hypertension, dyslipidemia, and diabetes had significantly less medication utilization (by 1-2 prescriptions) and lower adherence rates (by 0.05-0.09 in PDC; 0.04-0.13 in the proportion adherent). These reductions abated, yet remained, after 2 years among hypertension and dyslipidemia patients. The PDC was significantly lower in patients with depression by 0.07 and 0.05 after 1 and 2 years under the new plan, respectively. No statistically significant impacts were detected on enrollees with asthma/COPD.

A CDHP-HSA full replacement was associated with reduced adherence for 4 of 5 conditions. If this reduced adherence is sustained, it could adversely impact productivity and medical costs.