Is the number of prescribing physicians an independent risk factor for adverse drug events in an elderly outpatient population?

BACKGROUND: Studies indicate that adverse drug events (ADEs) are common and costly. It appears that the elderly are at greater risk of ADEs because they use more medications, have less specific presentations, and have more chronic conditions than younger populations.

OBJECTIVE: The goal of this study was to determine if the number of physicians prescribing medications to an elderly patient was associated with that patient's likelihood of reporting an ADE.

METHODS: This cohort study was a secondary analysis of data collected from a previous survey of Medicare managed care enrollees aged > or =65 years at the time of enrollment. A telephone survey of residents in the Philadelphia, Pennsylvania, area was conducted. Data included self-reported information on the number of prescribing physicians, chronic conditions, medications, ADEs, and general health status.

RESULTS: A total of 405 patients (mean [SD] age, 74 [5.1] years) were included in the study. Enrollees had a mean (SD) of 2.9 (1.3) prescribing physicians, and 98 (24%) patients reported having experienced an ADE in the previous 6 months. The mean (SD) number of self-reported chronic medical conditions and number of prescription medications was 4.7 (2.4) and 4.0 (2.8), respectively. In a multivariable logistic regression model, each additional provider prescribing medications increased the odds of reporting an ADE by 29% (odds ratio [OR], 1.3; 95% CI, 1.0-1.6). The number of chronic health conditions was also associated with ADEs. Having 4 or 5 self-reported chronic conditions doubled a person's odds of experiencing an ADE (OR, 2.1; 95% CI, 1.0-4.1) and having > or =6 conditions tripled the likelihood of experiencing an ADE (OR, 3.4; 95% CI, 1.6-6.9). The number of prescription medications or taking a potentially contraindicated medication was not significantly associated with self-reported ADEs.

CONCLUSIONS: In this study population, the number of prescribing physicians was an independent risk factor for patients self-reporting an ADE. More research is needed to confirm and explain this finding. One possibility is poor communication between multiple providers. Physicians should work to ensure more effective coordination of care between providers and communicate information about all medications prescribed to their patients with their colleagues.