Drug use patterns in severely mentally ill Medicare beneficiaries: impact of discontinuities in drug coverage.

Although implementation of the new Part D drug benefit is beneficial for Medicare beneficiaries previously without drug coverage, there is increasing concern that the benefit's “doughnut hole” design may result in reduced access to prescribed medicines (Stuart, Simoni-Wastila, and Chauncey 2005; Donohue 2006). Such discontinuities in drug coverage may be particularly detrimental to older and disabled individuals with chronic conditions, such as serious mental illnesses, for whom prescription drugs represent a necessary, even life-saving, treatment modality. Indeed, an analysis conducted using the Medicare Current Beneficiary Survey (MCBS) found that discontinuities in prescription drug coverage resulted in sizable reductions in drug use and spending (Stuart, Simoni-Wastila, and Chauncey 2005). Furthermore, these reductions in drug use and spending were disproportionately magnified in those beneficiaries experiencing chronic medical conditions, notably chronic obstructive pulmonary disease, diabetes, and mental illness. A growing body of literature demonstrates that older adults who have no prescription drug coverage utilize fewer drugs (Stuart and Coulson 1993; Adams, Soumerai, and Ross-Degnan 2001; Federman et al. 2001; Poisal and Murray 2001; Steinman, Sands, and Covinsky 2001; Mojtabai and Olfson 2003; Goldman et al. 2004; Piette, Heisler, and Wagner 2004). There also is a body of research documenting that prescription drug use and spending decline as individuals bear greater out-of-pocket expenses in copayments and deductibles (Cox et al. 2001; Cox and Henderson 2002; Saver et al. 2004), although little evidence relates to specific groups of elders or disabled, such as the severely mentally ill, who may be more vulnerable to such cost-sharing provisions. Despite this broad literature base, there is scant empirical evidence on the extent to which discontinuities in drug coverage affect drug use and spending among Medicare beneficiaries. In two survey-based analyses of Medicare HMO enrollees in plans with annual prescription benefit caps between $200 and $1,200, researchers demonstrated that many beneficiaries reduced their medication use after they exceeded the cap (Rector and Venus 2004; Tseng et al. 2004). A third study found aged Medicare beneficiaries suffering from common chronic conditions, including mental health disorders, experienced longer gaps in prescription drug coverage and, subsequently, experienced sizeable reductions in medication use and spending, relative to individuals with full prescription drug coverage (Stuart, Simoni-Wastila, and Chauncey 2005). Other research has established individuals with chronic conditions tend to be price sensitive in their demand for pharmacologic therapy (Soumerai et al. 1994; Blustein 2000; Stuart et al. 2004) and, therefore, may represent the individuals most likely to be affected by discontinuities in drug coverage, such as the Part D benefit “doughnut hole” design. In this study, we examine how discontinuities in drug coverage impact the use of medications used to treat psychiatric conditions by severely mentally ill Medicare beneficiaries. Severe mental illness (SMI) was chosen for several reasons: the importance of pharmacologic treatment modalities in treatment of mental disorders, the detrimental impact of mental illness on patients' quality of life and health, the relatively common prevalence of mental disorders among Medicare beneficiaries, and because prior research has demonstrated individuals with one or more mental conditions are disproportionately impacted by drug coverage gaps (Stuart, Simoni-Wastila, and Chauncey 2005). We have two study objectives: (1) to describe the extent of drug coverage possessed by severely mentally ill Medicare beneficiaries before Part D; and (2) determine whether and to what extent discontinuities in prescription drug coverage influence the use of prescription medications necessary in the treatment of serious mental health conditions.