Effect of cost sharing on screening mammography in Medicare health plans.

BACKGROUND: Policies that increase patients' share of health care expenses decrease the use of discretionary health services but also may reduce the use of important preventive care such as mammography. METHODS: We reviewed coverage for mammography within 174 Medicare managed-care plans from 2001 through 2004. Among 550,082 individual-level observations for 366,475 women between the ages of 65 and 69 years, we compared rates of biennial breast-cancer screening in plans requiring cost sharing for mammography with screening rates in plans with full coverage. We also performed a longitudinal analysis of screening rates in plans that changed from full coverage to cost sharing for mammography as compared with rates in matched control plans that did not institute cost sharing. RESULTS: The number of plans with cost sharing for mammography, which we defined as requiring a copayment of more than $10 or coinsurance of more than 10% for screening mammography, increased from 3 in 2001 (representing 0.5% of women) to 21 in 2004 (11.4% of women). Biennial screening rates were 8.3 percentage points lower in cost-sharing plans than in plans with full coverage, a difference that persisted in adjusted analyses (P