When a study published last month showed the proportion of Americans taking prescription drugs rose from 51% in 2000 to 59% in 2012, everyone asked (more or less), “Why?” and researchers answered (more or less), “It’s complicated.”
Lead author Elizabeth D. Kantor, an epidemiologist at Memorial Sloan Kettering Cancer Center in New York, told Managed Care that “a number of factors acting together likely explain the increase, and these factors likely vary by class of drug or individual drug.”
The aging population is not an explanation, Kantor and her coauthors said in the paper, which was published in the November 3 issue of JAMA. Medicare Part D might be, although Kantor and her colleagues proposed and then knocked down that possibility as a straw man, noting that the increase in prescription drug use has occurred among those younger than 65 and, what’s more, the trend lines started heading northward prior to 2006, the year that Part D went into effect.
|Most prescribed prescription drug classes, 2011–2012|
|Drug class||Prevalence of use||Prevalence ratio, 2011–2012/1999–2000|
|Anxiolytics, sedatives, hyponotics||6.1%||1.5|
|*Analysis limited to women.
Source: Kantor ED et al., JAMA, Nov. 3, 2015
Another contributing factor suggested by Kantor and her colleagues may be the best overall explanation: bulging American waistlines and the many drugs developed to treat the consequences. Kantor’s research shows that 8 out of the 10 most commonly used drugs in 2011–2012 (the years of the most recent data) were for conditions associated with being too heavy, including hypertension, diabetes, and dyslipidemia.
Kantor and coauthors analyzed data from seven cycles of the National Health and Nutrition Examination Survey (NHANES).
In addition to finding an increase in overall use, their analysis of the NHANES data shows that polypharmacy (the use of five or more drugs) is also trending upward. In fact, they found that it almost doubled, from 8.2% of the respondents in 1999–2000, to 15% in 2011–2012.
The most commonly prescribed drug class in 2011–2012 was antihypertensives (see table). The top 10 most prescribed individual drugs were simvastatin, lisinopril, levothyroxine, metoprolol, metformin, hydrochlorothiazide, omeprazole, amlodipine, atorvastatin, and albuterol. The study noted that, “all of the top 10 most commonly used drugs increased over the study period except atorvastatin.”
The “it’s complicated” idea is a theme of the paper. Prescription drugs are manufactured and sold in a “dynamic climate,” wrote Kantor and her coauthors, adding that “practice patterns are continually evolving to reflect the changing health needs of the population, advances in treatment, new clinical guidelines, the entrance or exit of drugs from the market, and shifts in policies regarding drug marketing and promotion.”
Simvastatin and atorvastatin are an example of the crosscurrents. The use of both increased in the early 2000s, but use of atorvastatin began to fall off after 2006, partly because simvastatin came off patent that year.
The guidelines tend to influence prescribing practices, so when the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure recommended that the thiazide diuretics be used as first-line agents in 2003, you’d expect prescriptions to go up then. But Kantor and her colleagues found an increase prior to 2003. In some cases, guidelines may be catching up with prescribing practices rather than determining them.