Rise in prescription copays puts different patients at risk for nonadherence to medications
Research Activities, July 2012, No. 383
As employers and insurance companies look to cut costs, consumers must face rising copays for prescription drugs. As a result, some individuals may start rationing their medications and either taking them less frequently or in smaller doses than recommended (nonadherence). Evaluation of copayment increase impacts commonly focus on average effects across a population, but a new study reveals that the effects of greater cost-sharing differs across patient subpopulations. Among veterans with diabetes or hypertension, those with lower comorbidity burden were more responsive to a $5 medication copayment increase than veterans with higher comborbidity burden (greater number of medical problems).
The researchers compared medication adherence among veterans with hypertension or diabetes at four Veterans Affairs (VA) medical centers after a rise in the copay for prescription drugs from $2 to $7 in 2002. Medication adherence among veterans required to pay copayments were compared to veterans exempt from drug copayment. There were propensity-score matched copaying and non-copaying groups for patients with hypertension (3,545 copay, 3,545 exempt) and for diabetes (1,069 copay, 1,069 exempt).
The results found that the pooled adherence change was largely driven by the two-thirds of the sample that had below average comorbidity burden. Medication adherence among diabetic veterans with low comorbidity burden was lower after the VA increased medication copayments (9.5% lower in the first 12 months after copayment increase and 4.9% in the subsequent 11 months thereafter). In hypertensive patients, veterans with low comorbidity burden were 3.7% less adherent to medications in the 13-23 months after copayment increases. Medication adherence rates did not change for diabetic and hypertensive veterans with high comorbidity burden.
These results suggest that presenting population-average effects may lead to incorrect policy inferences about the effectiveness of copayment increases on medication adherence. Due to heterogeneity in response to costsharing, a one-size-fits-all approach may not align patient and health system goals as effectively as intended. High-risk patients incur greater out-of-pocket costs from continued adherence, while low-risk patients put themselves at increased risk for adverse health events due to nonadherence induced by policy changes. The study was supported in part by the Agency for Healthcare Research and Quality (HS19479).
See "Does medication adherence following a copayment increase differ by disease burden?" by Virginia Wang, Ph.D., Chuan-Fen Liu, Ph.D., Chrisopher L. Bryson, M.D., M.S., and others in the December 2011 Health Services Research 46(6,pt1), pp. 1963-1985.