More than half of American adults have taken a prescription drug in the past month, according to research released Tuesday. (iStock)

Nearly 3 in 5 American adults take a prescription drug, up markedly since 2000 because of much higher use of almost every type of medication, including antidepressants and treatments for high cholesterol and diabetes.

In a study published Tuesday in the Journal of the American Medical Association, researchers found that the prevalence of prescription drug use among people 20 and older had risen to 59 percent in 2012 from 51 percent just a dozen years earlier. During the same period, the percentage of people taking five or more prescription drugs nearly doubled, to 15 percent from 8 percent.

One likely factor driving the increased use: obesity.

Researchers noted that eight of the 10 most commonly used drugs in the United States are for hypertension, heart failure, diabetes and other elements of the “cardiometabolic syndrome.” In addition, another frequently prescribed drug treats gastroesophageal reflux, a widespread condition among the overweight or obese.

[Why do drug companies charge so much? Because they can.]

Elizabeth Kantor, an epidemi­ologist at Memorial Sloan Kettering Cancer Center and co-author of the JAMA study, cautioned against drawing too many conclusions from the data. Although prescription drug use is increasing across most drug types, the reasons probably vary from drug to drug, she said. New medications hit the market, others lose their patent protection and public health officials revise their recommendations. Major policy changes have occurred, such as the implementation of Medicare Part D in 2006. All those factors can alter prescribing patterns and access to drugs.

“There’s so much going on in each area, it’s hard to draw concrete conclusions,” Kantor said. “Each drug class stands on its own.”

The country’s aging population would seem to be one obvious explanation, she noted. Yet after researchers adjusted for age, the trends toward increased prescription use held true.

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Kantor and her colleagues based their findings on data from the National Health and Nutrition Examination Survey, which involves a sample of about 5,000 people each year who reflect the U.S. population. In the survey, people were asked about their use of prescription drugs in the previous 30 days. The 2012 data was the most recent available.

Some other highlights from the study:

  • Use of sex hormones among women decreased from 19 percent to 11 percent over the period, a change driven largely by the decline in use of hormones to treat menopause.
  • The most commonly used individual drug in 2011-2012 was simvastatin, which is taken by roughly 8 percent of U.S. adults. It is a statin drug, often marketed under the brand name Zocor, which aims to lower cholesterol and reduce the risk of heart attacks and strokes.
  • Non-Hispanic white Americans take prescription drugs at roughly twice the rate of Mexican Americans. Researchers offered no clear explanation but said the disparity "was not entirely attributable" to differences in insurance status.
  • The use of antibiotics decreased from 5.7 percent to 4.2 percent.

The new study largely matches a similar report published two years ago by the Centers for Disease Control and Prevention, which found that from 2007 to 2010, about half of the U.S. population reported having taken at least one prescription drug over the previous month — with 10 percent taking five or more.

The CDC cited numerous factors potentially contributing to the trend, including the growth of third-party insurance and increased drug-marketing to doctors and directly to consumers.

The agency also noted that although the greater role of prescription drugs in U.S. health care had led to better treatment of heart disease, diabetes and other conditions, it also had contributed to serious problems such as the overprescribing of antibiotics and the ongoing overuse and abuse of prescription painkillers.

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