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

METHODS

Study Design and Sample

Data were from the 1996 Medical Expenditure Panel Survey Nursing Home Component (MEPS NHC), a survey of a nationally representative sample of NHs and residents. The MEPS NHC was primarily designed to provide national estimates of the use and expenditures for NH health services for all users of NHs at any time during 1996. Using a complex multistage study design, the MEPS NHC sampled NHs in the first stage and persons within selected NHs in the second stage. The sample included persons who were residents in NHs on January 1, 1996, as well as those who were admitted to NHs during the year (Potter 1998).

The MEPS NHC data were primarily collected from NH sources. Data on all medications prescribed for residents were obtained from NH medical charts and recorded for each calendar month that a person was a resident in an NH (including transfer facilities) during the year; however, drug data were not obtained for stays in non-NH facilities, such as acute care wings of hospitals. Information on drug name, form, strength, dosage, and frequency of administration were captured (Potter 1998).

This study included residents, aged 65 or older, who resided in an NH for at least three consecutive months during 1996. The minimum three-month stay allowed residents to have sufficient time to be exposed to the care provided in a given NH. Additional cases were excluded: 20 comatose residents, 5 residents missing all health insurance or drug data, 4 with no drugs administered, and 13 who lived in NHs that served primarily persons with mental illness and those with HIV/AIDS. The final study sample represented 1.6 million residents (n = 3,372), or 51 percent of all NH users in 1996.

Analyses used up to 12 months of drug data for each resident. About 23 percent of the study sample had at least one month of missing drug data, but among these, only 7 percent had drug data missing for more than half of the months of their NH stay. Reasons for missing drug data included refusals by the facility to provide information, inability to locate medical charts, and loss to follow-up (Potter, Lau, and Dominici 2002).

Measures

Potentially Inappropriate Medication (PIRx). Beers's criteria identified three types of PIRx: (1) inappropriate drug choice: medications that generally should be avoided among any elderly patients; (2) excess dosage: medications at a dose or duration that should not be exceeded for any elderly patients; and (3) drug-disease interaction: medications that should be avoided among certain elderly patients with specific comorbid conditions (Beers et al. 1991; Beers 1997). Residents were considered to have a PIRx exposure in a given month if any of the following conditions were met: (1) medication names matched the names of any drugs listed as inappropriate drug choice in Beers's criteria; (2) strengths and average dosages of medications matched the strengths and average dosages defined as excess dosage in Beers's criteria; or (3) residents had active diagnoses and took medications that matched any of the disease and drug combinations indicated as drug-disease interaction in Beers's criteria (Beers et al. 1991; Beers 1997). Residents with any PIRx exposure were those with any of the three types of PIRx exposure in one or more months during their NH stay.