In an attempt to improve diabetes outcomes, some employers and insurers have adopted Preventive Drug Lists (PDLs) that reduce out-of-pocket costs for antidiabetic and cardioprotective medications to $0. We sought to determine whether shifts to PDL coverage reduce acute diabetes complications and high-acuity outcomes among commercially insured patients with diabetes. Our study design was a natural experiment comparing changes in outcomes 1 year before and after the PDL switch in matched study groups. The Intervention group included 16,174 commercially-insured diabetes patients age 12-64 switched by their employers to PDL coverage; the Control group included 711,085 coarsened exact-matched contemporaneous patients whose employers offered no PDL. We conducted similar analyses in a subset of low-income members switched to PDL plans and their matched controls. Outcomes were acute diabetes complication visits, high-severity emergency department visits, and hospitalization days. Transition to the PDL was associated with a relative pre-post change of 1.6% (95% confidence interval, -7.2% to 10.3%) in acute diabetes complication visits, -3.2% (-14.4% to 8.1%) in high-severity emergency department visits, and 2.2% (-9.8% to 14.1%) in hospitalization days. Findings were similar in the low-income subgroup. We did not find detectable changes in acute diabetes complication visits and high-acuity outcomes among diabetes patients switched to low drug cost sharing health plans. Further research should assess longer-term outcomes and examine effects of reducing financial barriers to outpatient and emergency department care.


J. Wharam: None. M. Lakoma: None. F. Zhang: None. J. Wallace: None. L.F. Garabedian: None. S.B. Soumerai: None. D. Ross-Degnan: None.


National Institute of Diabetes and Digestive and Kidney Diseases; Centers for Disease Control and Prevention (5U18DP006122-05)

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