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Rise in obesity seen as a driver in Americans' increasing use of prescriptions

Prescription drug use has risen significantly in the United States during the past 15 years, and an increasing number of people are taking more than one prescription drug, according to a study published this week in JAMA, the journal of the American Medical Association.

Much of that increase appears linked to the growing obesity epidemic, the study’s authors say.

Specifically, the study found that 59 percent of American adults were on at least one prescription drug in 2011 and 2012, up from 51 percent in 1999 and 2000. During that same dozen years, the proportion of people taking five or more prescription drugs almost doubled, to 15 percent from 8.2 percent.

Let’s absorb that last statistic for a minute: About 1 in 7 Americans are taking five or more medications.

The new study used data from a nationally representative sample of about 38,000 American adults aged 20 and older who participated in the ongoing National Health and Nutritional Examination Survey (NHANES) between 1999 and 2012. Participants were asked during interviews in their homes if they had taken prescriptions drugs within the previous 30 days, and, if so, what those drugs were.
Possible explanations

The study’s authors — led by epidemiologist Elizabeth Kantor of the Memorial Sloan Kettering Cancer Center in New York City — note that the increase in prescription drug use is not explained by an aging population alone. For even after adjusting the findings for age, prescription drug use was significantly higher in 2011 and 2012 than in 1999 and 2000.

Nor does the implementation of Medicare Part D in 2006 have much to do with the increase. As Kantor and her colleagues point out, many of the biggest increases in prescription drug use observed in the study had already occurred before 2006. Furthermore, such drug use has risen among people in all age groups, not just those aged 65 or older.

For example, the proportion of people aged 65 and older taking five or more prescription drugs rose about 60 percent between 1999-2000 and 2011-2012, from 24 percent to 39 percent. But among people aged 20 to 39, the proportion more than quadrupled, jumping from 0.7 percent to 3.1 percent.

A stronger driver behind the rise in prescription drug use appears to be the rise of obesity with all of its related health problems.

"Eight of the 10 most commonly used drugs in 2011-2012 are used to treat components of the cardiometabolic syndrome, including hypertension, diabetes, and dyslipidemia," Kantor and her colleagues write. "Another is a proton-pump inhibitor used for gastroesophageal reflux, a condition more prevalent among individuals who are overweight or obese."

The use of drugs used to treat high blood pressure increased from 20 percent to 27 percent during the period of the study, for example, while the use of statins and other cholesterol lower drugs increased from 8 percent to 18 percent.

Indeed, the most commonly prescribed drugs in 2011-2012 were the cholesterol-lowering drug simvastatin (used by 7.9 percent of adults) and the blood-pressure-lowering drug lisinopril (used by 7.1 percent of adults).

In addition, drugs to treat type 2 diabetes have become more common. The anti-diabetic drug metformin was used by 4.9 percent of American adults in 2011-2012, making it the fifth most commonly prescribed drug in the United States.

Other findings

Another class of drugs that saw a significant increase in use was antidepressants. Almost twice as many Americans were taking these drugs in 2011-2012 (13 percent) than in 1999-2000 (7 percent).

One type of prescription drug actually fell out of favor during the 12 years of the study — hormonal medications used to “treat” menopause. The proportion of women taking such drugs fell from 19 percent in 1999-2000 to 11 percent in 2011-2012. This drop is almost certainly due to research linking the use of these drugs to an increased risk of stroke, cancer and other serious illnesses.

You can read the study in full on the JAMA website.