Less is known about the magnitude or types of underuse than of overuse, because it is difficult to measure an event that should have occurred but did not. Underuse of services has two principal sources: (1) underuse by virtue of lack of access to services and (2) underuse because patients are not offered (or do not accept) available services that are likely to be beneficial to them.
Access barriers are most often viewed in financial terms. They include the obstacles posed by lack of insurance coverage and by copayments and deductibles that deter use.10 For the Medicare beneficiary, lack of coverage for needed services (e.g., preventive services, dentures, glasses, or special shoes for diabetics) is an access barrier. The most often cited category of underuse of services is for ambulatory care, specifically preventive care (e.g., cancer screening, vaccination, and immunization). The value of preventive care for elderly is supported by a study conducted by Hermanson et al. (1988) showing that elderly smokers with coronary artery disease who ceased smoking had a lower risk of myocardial infarction and death than did continuing smokers. Home care and preventive care (virtually none of the latter being covered services) are widely regarded as underused elderly services.
Barriers to care may also be geographical, physical, or psychological. Beneficiary frailty and lack of transportation can preclude travel, even in urban or suburban areas. Unavailability of needed expertise and services in remote rural areas are equally obvious access barriers. Other possible obstacles to care are more directly related to Medicare. For instance, decisions by physicians not to accept Medicare patients may create an access barrier for patients; decisions not to accept assignment may impose the same obstacle for at least some Medicare beneficiaries. The complexity of the Medicare program itself may be an access barrier if patients (or their physicians) do not understand what services are covered or how to obtain care through Medicare. Beneficiaries for whom English is not the primary language are at particular risk from this access barrier.
Rules governing the frequency with which services covered by Medicare will be reimbursed in an ambulatory or institutional setting can also affect access, and there has been concern that the prospective payment system (PPS) for hospitals may lead to premature discharge and that capitation payment for HMOs may lead to undercare. Finally, differing decisions by fiscal intermediaries (FIs), carriers, and Medicare PROs concerning covered benefits or pre-admission and pre-procedure approvals can cause confusion and, perhaps, underuse of services for beneficiaries in some parts of the