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

Facility type was defined as hospital-based, multilevel care (including those with continuing care retirement communities and personal care units), or NH-beds only. Certification status indicated whether the NH was certified as a Medicare skilled-nursing facility, or Medicaid nursing facility. Accreditation status refers to accreditation by the Joint Commission on Accreditation of Healthcare Organizations (JCAHO) (Rhoades, Potter, and Krauss 1998). Both RN-to-non-RN and RN-to-resident ratios included only full-time employees, and not part-time or "pooled" staff. Selected technological services included four services: ventilator care, intravenous therapy, dialysis, and tube feeding. The percentage of residents vaccinated for influenza was estimated by NH respondents.

Census region and Metropolitan Statistical Area (MSA) were defined using the U.S. Bureau of the Census criteria (Rhoades and Sommers 2000). Two county-level characteristics were obtained from the 1998 Area Resource File (ARF): NH bed availability and income per capita. The former was defined by the number of empty NH beds per 1,000 people aged 75 and older; the smaller the value, the fewer NH beds available (Cohen and Spector 1996).

Statistical Analysis

All descriptive analyses and logistic regression analyses were performed using weighted data and SUDAAN software to account for the complex design of the MEPS NHC (Shah, Barnwell, and Bieler 1995). Univariate relationships and multivariate regression models were examined to identify resident and facility characteristics that were associated with either (1) any PIRx occurrences or (2) PIRx-severe. Three different specifications of the model were estimated, where the first specification contained only resident characteristics, the second specification contained only facility characteristics, and the final specification contained both resident and facility characteristics. The combined resident-and-facility multivariate models included variables that were statistically significant (p < 0.10) in either the model with resident characteristics or the model with facility characteristics. Key resident characteristics--age, sex, race, admission before 1996, and number of NH days in 1996--were kept in the combined model regardless of statistical significance.

RESULTS

Potentially Inappropriate Medication Prescriptions

Approximately 50 percent of all elderly residents with an NH stay of three months or longer received at least one PIRx in 1996 (Table 1). Among those residents with PIRx, 56 percent involved a single drug, 26 percent involved two different drugs, and 17 percent involved three or more different drugs. (The number refers to the number of different drug names that matched Beers's criteria and not frequency of exposure.) The type of PIRx varied: 40 percent of all NH residents had inappropriate drug choice, 11 percent had excess dosage, and 13 percent had drug-disease interaction. During 1996, PIRx exposure was rarely a single event. When PIRx occurred, a third of the residents (35 percent) had a PIRx for almost their entire NH stay (months with PIRx/ months in NHs [greater than or equal to] 90 percent). Among those residents living in the NH for the full year, more than one in five residents received a PIRx for every month of the entire year.