Robin A. Cohen, Whitney K. Kirzinger and Renee M. Gindi of the National Center for Health Statistics, part of the Centers for Disease Control and Prevention, said the study found nearly 12 percent of U.S. adults ages 18-64 didn't take prescribed medication to save money while nearly 6 percent of those age 65 and older didn't take medication due to the expense.
Adults ages 18-64 and those age 65 and older were equally likely -- about 20 percent -- to have asked a doctor for a lower-cost medication to save money on prescription drugs.
The researchers used data from the National Health Interview Survey, 2011.
Among adults aged 18-64, 23 percent of uninsured adults, 13.6 percent on Medicaid and 8.8 with private coverage, said they did not take medication as prescribed to save money.
Twenty-five percent of U.S. adults age 65 and older with only Medicare coverage asked doctors for lower-cost medication to save money while 20 percent with private coverage and 15 percent of those with Medicare and Medicaid coverage did, the study said.
Previous studies found more than 48 percent of Americans took at least one prescription drug in the past month, but some do not take medication as prescribed.
Adults who do not take prescription medication as prescribed have been shown to have poorer health and increased emergency room use, hospitalizations and cardiovascular events.
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