Prescription Drug Use Climbs Over 10 Years, but Cause Unclear

Tara Haelle

November 04, 2015

The use of prescription drugs and the prevalence of polypharmacy among US adults increased over the course of a decade, according to a study published November 3 in JAMA. Among the 11 drug classes that saw a jump were antidepressants, analgesics, prescription proton-pump inhibitors, muscle relaxants, antidiabetic drugs, and antihyperlipidemic agents.

"The increases in any prescription drug use and polypharmacy are not explained by changes in the age distribution of the population," write Elizabeth D. Kantor, PhD, MPH, from the Department of Epidemiology and Biostatistics at Memorial Sloan Kettering Cancer Center in New York City, and colleagues. "An alternative explanation for the observed increase in prescription drug use might be large-scale policy changes, including the implementation of Medicare Part D."

Yet Medicare Part D went into effect in 2006, which is after many of the biggest increases had already occurred, and prescription use climbed among adults younger than 65 years as well. Another potential driver is the increased prevalence of obesity, the authors suggest, which would lead to more treatment of weight-related health conditions.

"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," the authors write. "Another is a proton-pump inhibitor used for gastroesophageal reflux, a condition more prevalent among individuals who are overweight or obese."

The researchers compared results among the 37,959 adults aged 20 years and older who responded to the seven National Health and Nutrition Examination Surveys from 1999-2000 through 2011-2012. The respondents provided information on their use of prescription drugs in the previous 30 days.

Between the 1999-2000 survey and the 2011-2012 survey, the proportion of adults reporting any use of prescription drugs increased from an estimated 51% to an estimated 59% (P for trend < .001). Similarly, the proportion of adults reporting use of at least five prescription drugs increased from an estimate of 8.2% in 1999-2000 to 15% in 2011-2012 (difference, 6.6%; 95% confidence interval, 4.4% - 8.2%; P for trend < .001). Simvastatin was the most commonly used drug in 2011-2012, with 7.9% of all US adults taking it, up from 2% of adults in 1999-2000.

Although most, but not all, drug classes showed an increase, the authors discussed a few notable increases in particular: Increased prescriptions for statins primarily drove the climb in antihyperlipidemic use, particularly before 2005-2006, even though the American College of Cardiology and American Heart Association did not release their recommendations expanding guidelines for statin use until 2013.

Meanwhile, changing attitudes in society most likely played a role in the increase in antidepressant use, mostly selective serotonin reuptake inhibitors (SSRIs) and serotonin-norepinephrine reuptake inhibitors. "Even so, SSRIs remain much more commonly used than the other antidepressant drugs, and the continued popularity of the SSRIs may reflect the availability of several generic options with a wide range of indications and a favorable profile regarding adverse effects," the authors write.

Although overall analgesic trends remained stable, use of narcotic analgesics particularly increased, with some stabilizing after 2003-2004. "This flattening trend may reflect increased awareness of prescription opioid drug misuse or abuse, although underreporting of these drugs may have increased with awareness regarding their potential for abuse," the authors write.

Women's use of sex hormones decreased, even though conjugated estrogens were previously among the most commonly used drugs. Antidiabetic drugs, especially insulin and biguanides, have increased with the prevalence of diabetes, and metformin is now the fifth most commonly used drug.

With one exception, few differences showed up among different groups based on age, sex, and race/ethnicity for most drugs and drug classes. The exception, a lower use of prescription drugs among Mexican Americans, remained after adjustments for age and insurance status. A possible explanation for this, the authors note, is "the Hispanic paradox, which is that despite lower socioeconomic status, individuals of Hispanic descent have better-than-expected health status, which would likely result in less use of prescription medications."

The research was funded by the National Cancer Institute and the National Institute of Diabetes and Digestive and Kidney Diseases with additional support from Harvard Catalyst–The Harvard Clinical and Translational Science Center and financial contributions from Harvard University and its affiliated academic healthcare centers. One coauthor reported he has consulted for Pfizer Inc, Bayer Healthcare and Pozen Inc. The other authors have disclosed no relevant financial relationships.

JAMA. 2015;314:1818-1831. Full text

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