For this study, in-home interviews, including medication logs, were administered to people aged 57 to 85 between (OTC), and dietary supplements used "on a regular schedule, like every day or every week." Concurrent use was defined as the regular use of at least two medications.
Prescription and nonprescription medications were commonly used together, with nearly one in 25 individuals potentially at risk for a major drug-drug interaction, according to results. Research was funded by the National Institutes of Health and the University of Chicago.
Overall, 1 in 25 older adults risked serious drug interactions, the study found. For men ages 75 to 85, it was as high as 1 in 10.
The unweighted survey response rate was 74.8% (weighted response rate, 75.5%). Eighty-one percent (95% confidence interval [CI], 79.4%-83.5%) used at least 1 prescription medication, 42% (95% CI, 39.7%-44.8%) used at least one OTC medication, and 49% (95% CI, 46.2%-52.7%) used a dietary supplement.
Twenty-nine percent (95% CI, 26.6%-30.6%) used at least 5 prescription medications concurrently; this was highest among men (37.1%; 95% CI, 31.7%-42.4%) and women (36.0%; 95% CI, 30.2%-41.9%) aged 75 to 85 years.
Among prescription medication users, concurrent use of OTC medications was 46% (95% CI, 43.4%-49.1%) and concurrent use of dietary supplements was 52% (95% CI, 48.8%-55.5%).
Overall, 4% of individuals were potentially at risk of having a major drug-drug interaction; half of these involved the use of nonprescription medications. These regimens were most prevalent among men in the oldest age group (10%; 95% CI, 6.4%-13.7%) and nearly half involved anticoagulants. No contraindicated concurrent drug use was identified.