UCSF

Background and objective

Quality prescribing for older adults involves multiple considerations. We evaluated multiple aspects of prescribing quality in older veterans to develop an integrated view of prescribing problems and to understand how the prevalence of these problems varies across clinically important subgroups of older adults.

Design and participants

Cross-sectional observational study of veterans age 65 years and older who received medications from Department of Veterans Affairs (VA) pharmacies in 2007.

Main measures

Using VA pharmacy data linked with encounter, laboratory and other data, we assessed five types of prescribing problems.

Key results

Among 462,405 patients age 65 and older, mean age was 75 years, 98 % were male, and patients were prescribed a median of five medications. Half of patients (50 %) had one or more prescribing problems, including 12 % taking one or more medications at an inappropriately high dose, 30 % with drug-drug interactions, 3 % with drug-disease interactions, and 26 % taking one or more Beers criteria drugs. In addition, 16 % were taking a high-risk drug (warfarin, insulin, and/or digoxin). On multivariable analysis, age was not strongly associated with four of the five types of prescribing issues assessed (relative risk < 1.3 across age groups), and comorbid burden conferred substantially increased risk only for drug-disease interactions and use of high-risk drugs. In contrast, the number of drugs used was consistently the strongest predictor of prescribing problems. Patients in the highest quartile of medication use had 6.6-fold to12.5-fold greater risk of each type of prescribing problem compared to patients in the lowest quartile (P < 0.001 for each).

Conclusions

The number of medications used is by far the strongest risk factor for each of five types of prescribing problems. Efforts to improve prescribing should especially target patients taking multiple medications.