Potentially inappropriate medication prescriptions among elderly nursing home residents: their scope and associated resident and facility characteristics

Health Services Research, Oct, 2004 by Denys T. Lau, Judith D. Kasper, D.E.B. Potter, Alan Lyles

With pharmaceuticals being a principal mode of therapy, nursing home (NH) residents, on average, take 5 to 9 different medications daily and over 20 percent use more than 10 medications (Avorn and Guracitz 1995; Bernabei et al. 1999). High medication use poses significant risk to elderly residents for adverse drug reactions because their altered physiological drug metabolism heightens their sensitivity to various drug effects. With more comorbidity and greater medication consumption, elderly patients have increased chances of exposure to potentially inappropriate medication (PIRx), such as drug-disease and drug-drug interactions (Gurwitz et al. 2000; Beers et al. 1992).

Even though PIRx is a major policy concern because of its preventability, and implications for patient safety (Hanlon et al. 2000; Stuart and Briesacher 2002), determining which medications are inappropriate for elderly patients is not straightforward, especially in the absence of widely accepted prescribing guidelines for the elderly. Perhaps the most cited criteria are those developed by Beers and colleagues (1991, 1997), who convened panels of multidisciplinary experts to develop consensus guidelines for PIRx that generally should be avoided among elderly patients. Using only a subset of Beers's criteria, earlier studies in selected populations and geographic areas suggested that a substantial proportion of long-term care residents received PIRx (Aparasu and Mort 2000). The lowest rate of PIRx (25 percent) was reported in a study of elderly residents living in board and care facilities (Spore et al. 1997). Other studies reported higher rates of PIRx among Medicaid patients: 33 percent of NH residents in Kentucky and 49 percent of intermediate care facility residents in Louisiana (Gupta, Rappaport, and Bennett 1996; Piercoro, Browning, and Prince 2000). Using his own criteria, Beers found that 40 percent of residents in skilled nursing facilities near Los Angeles had at least one PIRx (Beers et al. 1992).

Quality of care and patient safety have received renewed attention due to recently published Institute of Medicine reports (Institute of Medicine 2001; Kohn, Corrigan, and Donaldson 1999; Wunderlich and Kohler 2001). This study examines PIRx in the NH setting using both versions of Beers's criteria (1991, 1997), which include three types of PIRx: inappropriate drug choice, excess dosage, and drug-disease interactions. Even though Beers's 1991 criteria were developed for elderly NH residents, and the 1997 criteria for community-dwelling elderly, it is appropriate to use the 1997 criteria to analyze PIRx among NH residents because elderly NH residents generally are more frail and sick, and may be more sensitive to drug effects than their community-dwelling counterparts. Drugs that are identified as PIRx for community-dwelling individuals should pose similar, if not greater, risks of adverse side effects for persons living in NHs.

The present study analyzes data from a nationally representative sample of NHs and residents to determine the scope of PIRx in the United States. Previous studies using national data sources have analyzed PIRx among community-dwelling elderly patients (Zhan et al. 2001), and those receiving care at outpatient departments or physician offices (Aparasu and Fliginger 1997; Goulding 2004; Mort and Aparasu 2000).

In addition to the prevalence, this study investigates the influence of two types of risk factors--resident and facility characteristics--on having PIRx exposure in the nursing home setting. Based on prior studies, we expect that the risk of PIRx exposure will vary across resident characteristics because of differences in health factors (mental health, physical limitations, and behavior and communication problems), the complexity of drug regimens (number of medications), and insurance status. Residents with mental disorders (Schmidt et al. 1998), on greater number of medications (Piercoro, Browning, and Prince 2000; Spore et al. 1997), and on Medicaid (Gupta, Rappaport, and Bennett 1996; Piercoro et al. 2000) have been found to be at higher risk of having PIRx exposure. Because residents are not randomly distributed among nursing homes, it is necessary to control for resident characteristics when examining nursing home characteristics. The variables selected (age, sex, race, marital status, number of living children, education, and poverty status) include both predisposing and enabling characteristics in the conceptual frameworks of healthcare utilization (Andersen 1995). Their role in quality of care is less well understood and they are included here primarily as background variables. Identifying resident characteristics that are associated with PIRx could serve as markers to target quality improvement initiatives, such as care planning and drug regimen reviews.

Furthermore, we are examining facility characteristics that are associated with having PIRx. It is clear that facility-level approaches to quality improvement and patient safety may be among the most effective (Institute of Medicine 2001; Kohn, Corrigan, and Donaldson 1999). We expect that the risk of PIRx will vary across characteristics associated with the organizational structure (ownership, size, and type), nurse staffing levels (ratio of registered nurses to nonregistered nurses, and ratio of nursing staff to patients), regulatory indicators (certification by Medicaid and Medicare, accreditation by the Joint Commission on Accreditation of Healthcare Organizations, and presence of consultant pharmacist onsite), high-level technological services (such as ventilator care, intravenous therapy, dialysis, and tube feeding), and geographical locations (census region, metropolitan versus rural area, and the income-per-capita of the neighborhood). Facilities that had for-profit ownership (Harrington et al. 2001), a greater number of beds (Beers et al. 1992), poor nurse staffing levels (Harrington et al. 2000; Schmidt et al. 1998), as well as facilities that did not offer high-level technological services and were situated in poorer neighborhoods (Cohen and Spector 1996), were found to be associated with having either PIRx exposure or poor overall quality of patient care. Findings of this study will help us better understand the roles of resident and facility characteristics in PIRx exposure and can help inform the process of developing strategies to improve pharmaceutical services in nursing homes.