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Kaufman DW, Kelly JP, Rosenberg L, Anderson TE, Mitchell AA. Recent Patterns of Medication Use in the Ambulatory Adult Population of the United States: The Slone Survey. JAMA. 2002;287(3):337–344. doi:10.1001/jama.287.3.337
Author Affiliations: Slone Epidemiology Unit, Boston University School of Public Health, Boston, Mass.
Context Data on the range of prescription and over-the-counter drug use in the
United States are not available.
Objective To provide recent population-based information on use of all medications,
including prescription and over-the-counter drugs, vitamins and minerals,
and herbal preparations/natural supplements in the United States.
Design, Setting, and Participants Ongoing telephone survey of a random sample of the noninstitutionalized
US population in the 48 continental states and the District of Columbia; data
analyzed here were collected from February 1998 through December 1999.
Main Outcome Measure Use of medications, by type, during the preceding week, compared by
Results Among 2590 participants aged at least 18 years, 81% used at least 1
medication in the preceding week; 50% took at least 1 prescription drug; and
7% took 5 or more. The highest overall prevalence of medication use was among
women aged at least 65 years, of whom 12% took at least 10 medications and
23% took at least 5 prescription drugs. Herbals/supplements were taken by
14% of the population. Among prescription drug users, 16% also took an herbal/supplement;
the rate of concurrent use was highest for fluoxetine users, at 22%. Reasons
for drug use varied widely, with hypertension and headache mentioned most
often (9% for each). Vitamins/minerals were frequently used for nonspecific
reasons such as "health" (35%); herbals/supplements were also most commonly
used for "health" (16%).
Conclusions In any given week, most US adults take at least 1 medication, and many
take multiple agents. The substantial overlap between use of prescription
medications and herbals/supplements raises concern about unintended interactions.
Documentation of usage patterns can provide a basis for improving the safety
of medication use.
A large number and wide variety of medications approved for use by the
US Food and Drug Administration (FDA) are available to the US population,
and expenditures on drugs have increased dramatically in recent years.1-3 New prescription drugs
are continually introduced, and older drugs are increasingly available over
the counter (OTC), making self-medication commonplace. Adverse reactions to
drugs are among the leading causes of hospitalization and death in this country.4,5 At the same time, there has been a
considerable increase in the use of herbal products and other natural supplements6,7 (henceforth referred to as "herbals/supplements"),
which by law are not subject to FDA regulation. Although these products may
be taken concurrently with regulated medications, health care professionals
are often not informed of such use by their patients.7
Evidence is growing that many herbals/supplements have pharmacologic activity
that can lead to clinically serious adverse interactions when they are taken
together with regulated drugs,8 but there is
little information available to estimate the potential magnitude of this problem.
More generally, despite the substantial commitment of resources from
government, industry, and others to evaluate drug effects, no ongoing information
exists on the degree to which the US population is using the broad range of
medications, including prescription and OTC drugs, vitamins/minerals, and
herbals/supplements. To help meet this need, the Slone Epidemiology Unit of
Boston University is conducting an ongoing telephone survey of a random sample
of the noninstitutionalized continental US population. In this first report,
we focus on general patterns of medication use in the ambulatory US adult
population in 1998 and 1999.
Residents of households in the 48 contiguous states and the District
of Columbia are eligible for inclusion in the survey. Not eligible are those
without telephones; individuals residing in vacation homes for less than 3
consecutive months, nursing homes, rehabilitation hospitals, or "group homes"
(eg, halfway houses); and individuals in prisons, military barracks, or college/university
dormitories without telephones in individual rooms.
Subjects are identified by random digit dialing (RDD); a 2-stage sampling
procedure9 is used to generate the telephone
numbers to be called. At least 20 attempts are made to contact the targeted
numbers over a 1- to 2-month period before a number is considered unreachable.
At each contacted number, 1 individual in the household is selected for interview
by a computer-generated random number procedure. Persons 14 to 17 years old
are interviewed only with the permission of a parent or guardian; for children
younger than 14 years and subjects incapable of responding to the questions
because of conditions such as Alzheimer disease, a surrogate (parent, spouse,
or caretaker) who has knowledge of all the subject's medications is interviewed.
Currently, interviews are conducted in English or Spanish. For subjects who
only speak another language, the interview is conducted in English if someone
is present who can act as an interpreter. In the future, the use of an interpreter
service is planned.
Information is recorded on prescription and nonprescription drugs, vitamins/minerals,
and herbals/supplements. The last group includes plant extracts except those
marketed in regulated drugs (eg, senna laxatives), amino acids, animal extracts,
enzymes, and other unclassified agents (eg, glucosamine).
The interviewer explains that information is being sought on any amount
of use of all medications taken during the preceding 7 days and asks the subject
to gather the relevant bottles or packages. A list of reasons for use (eg,
pain/headache/backache, depression/tension/emotional disorders) is then read
to elicit recall of medications not covered by the bottles. In addition, a
short list of trade names of selected drugs is read. After the names of all
reported medications have been recorded, the following information is obtained
for each: reason for use, route of administration, number of days taken in
the week before the interview, and total duration of the current episode of
use. For products containing aspirin, acetaminophen, ibuprofen, or conjugated
estrogens, the dose and number of pills per day are also obtained.
Other information elicited includes age, sex, race (using the 1990 US
Census categories10), Hispanic origin, years
of education, income (in ranges), whether the subject has prescription coverage
through health insurance, ZIP code of residence, and for women aged 18 to
50 years, pregnancy status (including due date or last menstrual period).
Medication names are coded for analysis using a dictionary developed
and maintained by the Slone Epidemiology Unit. The dictionary is a computerized
linkage system composed of individual agents and multicomponent products,
including herbals/supplements, each assigned specific code numbers. All combination
products are linked to their individual components. Thus, groupings of drugs
that contain a particular entity (eg, aspirin-containing products) can be
The survey was initiated in February 1998; this article covers data
collection through the end of December 1999. During that time, we attempted
to contact 10 354 telephone numbers, of which 5279 were clearly not eligible
residential numbers, and 562 could not be contacted; we assumed that 10% of
the latter (ie, 56 numbers) were residences, leaving 4569 eligible numbers.
From these, there were 783 refusals, 207 unsuccessful attempts to interview
for reasons other than refusal (eg, hearing problems or unable to interview
within the specified time limit), the 56 not-contacted numbers assumed to
be eligible, 318 with unresolved status when the data file was closed for
analysis, and 3205 interviews. Some information was available about the characteristics
of the 990 refusals and "unsuccessful interviews" in terms of age (known for
10%), sex (27%), number in household (32%), and region (100%). These nonparticipating
subjects were somewhat more likely to be men than the participating subjects
(54% vs 46%), but the distributions according to the other factors were similar.
A total of 71 interviews were eventually conducted from the group of 318 with
unresolved status, but are not included in this report. Thus, the overall
participation rate was 72% of the eligible subjects (3276/4569).
From the 3205 interviews in the analytical file, we excluded 22 that
were conducted early in the project because the random selection within the
household was not done properly, and 3 in which the subject's age or sex was
not recorded. Thus, 3180 interviews were available for analysis, of which
370 were completed in 1998 when the survey was conducted on a smaller (but
still national) scale, and 2810 in 1999. Among 2590 subjects at least 18 years
of age, 183 interviews were conducted with surrogates. Among 590 younger subjects,
493 interviews were conducted with parents.
We compared demographic information on all 3180 interviews to data from
US Census projections for 1998 and 2000.11-15
For the comparison of the racial/ethnic distribution, the 1990 Census data10 were used because the categories were defined differently
in the 1998 and 2000 projections. The probability of selection within each
household, which is inversely related to household size, was allowed for by
weighting the survey data according to that factor. The subjects included
in the Slone Survey generally reflected the US population. The distribution
according to race was similar (white: 77% in the survey with 60 refusing to
answer, 80% in the United States) and the proportion living within each of
4 broad regions (Northeast, Midwest, South, and West) was within 2% of the
US Census figures. The age and sex distributions of study participants were
similar to the United States (median age, 34 years; 35 years in the United
States; 53% women, 51% in the United States). The Slone Survey included somewhat
fewer single-person households (22% vs 26%) and fewer individuals of Hispanic
origin (9% vs 12%). The only material differences were that survey subjects
had more education (30% college graduate vs 21%) and higher annual household
incomes (58% with at least $35 000 vs 55%). Thirteen percent of study
participants refused to answer the income questions.
Our results are based on the 2590 subjects who were at least 18 years
of age. One-week prevalence is reported, ie, any use during the 1-week period
preceding the interview. We elected not to include topical vitamins/minerals
and topical herbals/supplements in this analysis because of the likelihood
of incomplete reporting of the use of such products. Topical drugs and eyedrops
were included. All percentages are adjusted for household size. As examples
of the precision of the results, in the full sample of 2590, estimates of
1% are accurate to ±0.4%, estimates of 10% to ±1.2%, estimates
of 20% to ±1.5%, and estimates of 50% to ±2%. In the smaller
subgroups (eg, women aged 45-64 years), the accuracy is lower.
As shown in Figure 1, 81%
of the subjects had taken at least 1 medication (prescription or OTC drug,
vitamin/mineral, or herbal/supplement) during the preceding week. Rates of
use increased with age and were greater in women than men in every age group,
with the exception that among persons 65 years or older, the proportions who
took at least 10 medications were the same. The highest overall prevalence
was among older women, of whom 94% had taken at least 1 medication, 57% took
5 or more, and 12% took 10 or more. The lowest prevalence was among 18- to
44-year-old men, of whom 68% took at least 1, 7% took at least 5, and fewer
than 1% took 10 or more drugs in the preceding week. The overall prevalence
of medication use varied somewhat by race/ethnicity: 84% among both whites
and Native Americans, 76% among those who identified their race as black or
African American, 75% among those of Hispanic origin, and 57% among Asian/Pacific
After adjustment for sex and household size, the overall prevalences
for use of any medications, at least 5 medications, and 10 or more medications
were within 2% of the results in Figure 1. The corresponding figures adjusting for education in addition
to household size were within 1%. The exclusion of 183 surrogate interviews
did not change the estimates.
Prescription drug use (excluding drugs that are available both by prescription
and OTC, such as naproxen) is shown in Figure
2. Fifty percent of subjects reported taking at least 1 prescription
drug during the previous week and 7% took 5 or more. Prescription drugs were
used more frequently by women than men, and by older than younger persons.
Among older women, 23% took 5 or more prescription drugs during the preceding
week; among older men, 19% used at least 5 prescription drugs.
The 40 most commonly used prescription and OTC drug entities, taken
either as single- or multiple-component products, are listed in Table 1. Although almost two thirds (27) are available only by prescription,
6 of the 10 most frequently used drugs, including the top 4, are available
OTC. The most frequently used entities were acetaminophen, ibuprofen, and
aspirin. Multiple-ingredient preparations accounted for 45% of acetaminophen
and 26% of aspirin use. By contrast, only 2% of ibuprofen products were combination
products. The most frequently used prescription-only drugs were conjugated
estrogens (fifth overall), thyroid supplement (seventh), an estrogen contained
in oral contraceptives (eighth), and a diuretic (10th).
Some of the drugs had strong sex- or age-specific patterns of use. For
example, aspirin was most commonly taken by older men, among whom 58% of the
users took it for cardiovascular prophylaxis. Aspirin use was also quite common
among older women: 51% of those users took it for cardiovascular prophylaxis.
Among middle-aged women who reported taking conjugated estrogens, 45% used
medroxyprogesterone concomitantly. Atorvastatin, furosemide, warfarin, and
digoxin were most frequently used by older men; levothyroxine, amlodipine,
hydrochlorothiazide, triamterene, and diltiazem were most frequently taken
by older women; diuretics and antihypertensives were more commonly used in
the older age groups; ibuprofen and caffeine (not including caffeine in beverages
or food) were more frequently used by younger subjects.
Vitamins/minerals were taken in the week before interview by 40% of
the population. Table 2 presents
rates for the 10 most commonly used entities. Multivitamins, defined as products
containing at least 4 different vitamins (B vitamins are counted only once),
were the most common, taken by about one fourth of the individuals. The listed
specific vitamins and minerals reflect the prevalence reported for products
other than multivitamins. The most common of these were vitamin E, vitamin
C, and calcium, either alone or in combination with 2 or fewer other components.
The total prevalence of use of specific compounds contained in multivitamins
is the sum of the use of the individual agent and the use of multivitamins.
Thus, for example, the total usage of vitamin E was approximately 36% (26%
multivitamin plus 10% other vitamin E use), and of folic acid, 28%. The prevalence
of vitamin and mineral use was higher among middle-aged and older subjects
of both sexes, and generally higher among women than among men.
Fourteen percent of the population had taken at least 1 herbal/supplement
in the preceding week. As shown in Table
3, overall use for each of the 10 most common entities ranged between
0.9% and 3.3%. Among both men and women, the most frequent users of these
preparations tended to be middle-aged. Exceptions include creatine, which
was most commonly taken by younger men; glucosamine and Serenoa repens, taken by older men; and Ginkgo biloba, taken by older women.
Table 4 provides the 10
most commonly reported reasons for use of prescription and OTC drugs, vitamins/minerals,
and herbals/supplements. For regulated drugs, these were hypertension, headache,
"heart," allergy, and unspecified pain. Three percent of the reasons for use
were reported as "don't know/no reason specified." By far the most common
reason given for use of vitamins/minerals was "health/good for you"; the next
most common was "diet supplement." Prophylaxis was a frequently cited reason,
most often for osteoporosis and colds/influenza. For 3% of vitamin/mineral
use, the reason was "don't know/no reason specified." For herbals/supplements,
the most frequently reported reasons were "health/good for you," arthritis,
and memory improvement; "don't know/no reason specified" was reported for
2% of the use.
Lacking diagnostic documentation, the survey data do not provide medically
confirmed information about the appropriateness of drug use. Rather, the survey
was designed to reflect respondents' perceived reasons for why they were taking
specific medications. Nonetheless, insights about whether drugs are being
used for their intended purposes can be gained. As one example, 95% of the
drugs taken for hypertension were products approved for that indication (eg,
atenolol, amlodipine). Examined from a different perspective, among individuals
who had used lisinopril (the most frequently reported antihypertensive drug),
78% gave hypertension as the reason, 12% reported indications possibly related
to hypertension but less clearly so (eg, unspecified heart disease), and the
remaining 11% either did not know the reason or stated that their physician
had recommended the drug. Patterns observed for other reported reasons for
use consistently reflected that patients' perceptions generally correlated
with the approved indications for the drugs they were taking.
Overall, 16% of prescription drug users also reported use of 1 or more
herbals/supplements. Among users of the 40 most common prescription and OTC
drugs (Table 1), concomitant use
of herbals/supplements during the same 1-week period ranged from 7% among
paroxetine users to 20% or more for users of simvastatin (20%), conjugated
estrogens (21%), and fluoxetine (22%).
With rapidly increasing medical care costs, concerns are growing about
the benefits and risks of the wide range of prescription and OTC medications.
Dramatic increases in the use of herbals/supplements has prompted similar
concerns about those products, both alone and in combination with FDA-regulated
pharmaceuticals. However, verification and quantification of the clinical,
research, and public health implications of these concerns has been limited
by the absence of comprehensive information on exposures to the full range
of medications in the general population. This survey was developed to provide
Our findings confirm that large numbers of US adults take large quantities
of medications. In 1998-1999, more than 80% of the adult population took at
least 1 medication in the preceding week, and 25% took at least 5. These rates
translate into 169 million and 52 million individuals, respectively. Even
among the group with the lowest rate of use, men 18 to 44 years of age, more
than two thirds took at least 1 medication during a given week. Use of prescription
drugs is also widespread: half of US adults took at least 1 drug and 7% took
at least 5. For the Medicare population, women 65 years or older had the highest
prevalence of medication use in our data: 94% took at least 1, 57% took 5
or more, and 12% took 10 or more, translating to 19, 12, and 1.4 million older
women, respectively. Use of prescription drugs was also highest among this
group, with rates of 81% and 23%, respectively, for at least 1 and at least
5 drugs. Men 65 years or older also reported high prevalence of medication
use, although not quite as high as among older women.
Among FDA-regulated drugs, OTC analgesics were the most frequently used
individual products, taken by 17% to 23% of the population. Prescription drugs
predominated among the remaining commonly used compounds. The most common
prescription drugs among women were conjugated estrogens and thyroid supplements,
while among men they were cardiovascular drugs and diuretics. Antiulcer agents
and cholesterol-lowering drugs were also commonly used prescription drugs.
Among OTC agents, decongestants and antihistamines followed analgesics in
frequency of use.
Forty percent of the population took 1 or more vitamin or mineral supplements
(the same prevalence reported from the National Health and Nutrition Examination
Survey [NHANES] III, a national survey conducted in 1988-199416).
The most commonly used products, by far, were multivitamins (26%).
Herbals/supplements are widely used in the United States: 14% of the
survey respondents had used at least 1 of these products in the preceding
week. The most common individual herb, ginseng, was taken by 3.3% of the population.
In a survey conducted in 1997, Eisenberg et al7
observed a prevalence of 12% for use of any herbal preparation in a 1-year
period. That represented a substantial increase from the 2.5% prevalence reported
by the same investigators from a similar survey conducted in 1990.6 The figures reported by Eisenberg et al are not directly
comparable to those in this survey, since the exposure period was 1 year rather
than 1 week, and the definition of "herbal preparations" may not have included
some of the other natural supplements that we considered. More directly comparable
are the NHANES III data from 1988-1994, in which the 1-month prevalence of
use of any supplement other than vitamins or minerals was 3.6%,17
substantially lower than our current observation of a 14% 1-week prevalence
from a decade later.
While information on indications for drug use is typically derived from
medical sources or inferred from the product name, our data provide the users'
own perceptions of reasons they are taking medications. The distribution of
stated reasons for use varied across type of medication, but our examination
of selected prescription drugs showed that, with few exceptions, patients
report indications that are compatible with the prescribers' likely intent.
For vitamins/minerals, which are commonly self-prescribed, almost half of
all use was accounted for by "health/good for you" and "diet supplement."
"Health/good for you" was also a common reason for taking herbals/supplements,
although the large majority of users were taking these products to achieve
more specific health goals. For all 3 classes of medications, 2% to 3% of
users did not know or could not specify a reason they were taking the product.
As increasing numbers of reports describe clinically serious interactions
between prescription drugs and herbals/supplements and as more is learned
about the pharmacologic actions and metabolic pathways of the latter compounds,
concern has grown that the problem of interactions may be substantial but
unrecognized.8 Our data document that patients
taking prescription drugs frequently take herbals/supplements concurrently,
lending support and direction to those concerns. This finding also emphasizes
the importance of clinicians inquiring about their patients' use of herbals/supplements,
since knowledge of concurrent use can help identify patients at risk for potential
To our knowledge, this is the first population-based survey to provide
comprehensive information on use of the broad range of medications, including
herbals/supplements, in the United States. Until now, most information on
use of regulated drugs has been derived from sales data or reports of dispensed
prescriptions. These sources are typically proprietary and unpublished, and
they do not measure use by individual patients. Overall rankings of specific
drug products by sales are readily available,18,19
but that information does not necessarily reflect actual use of the drugs.
Sales data do not provide information on characteristics of users or details
such as perceived indications or concurrent medications that have direct clinical
relevance to compliance and drug interactions. The product sales rankings
are not directly comparable to our results, which provide information on the
actual use of drug entities that may be contained in multiple products.
In recent years, limited population-based surveys have focused on use
of selected drugs in subpopulations,20-24
and a few have provided a wider range of information on subpopulations, particularly
There have also been intermittent surveys of the general population regarding
specific classes of drugs or supplements, eg, dietary supplements in 19906 and again in 1997.7
The NHANES III16,17,28-30
was a more general survey in which a nationally representative population
was interviewed during 1988-1994, with information obtained on use in the
prior month of all prescription drugs and dietary supplements. However, only
selected OTC drugs were included.16,17,28
The survey population in this report is similar to the US population
based on comparisons with US Census data. Most differences identified were
small. Our study included fewer individuals of Hispanic origin than the general
population, but otherwise the ethnic distribution of the survey population
was similar to the US Census figures. The survey population was generally
representative in terms of household size, except for somewhat fewer single-person
households, which may reflect the greater difficulty in reaching a household
occupied by only 1 person. The largest difference was a deficit of survey
subjects from lower socioeconomic levels. Both this underrepresentation and
the slight excess of women participants are known aspects of RDD surveys.31 The overall results after adjustment for education
and sex were similar to the unadjusted findings.
The possibility of bias due to differences in medication use between
participants and nonparticipants cannot be excluded. However, our participation
rate of 72% is quite high for such studies: participation in academic RDD
surveys has been reported to range from 22% to 70%, with a median of 50%.32 The information that was available on the characteristics
of the nonparticipants indicated that the only material difference was a modest
excess of men. The overall sex-adjusted usage rates were similar to the unadjusted
rates, and most results were provided separately for men and women.
Another potential source of error is differential reporting of the use
of specific products. The interview process was carefully designed to minimize
this problem. All interviewers were rigorously trained to conduct the interviews
in a consistent manner, the exposure interval of interest was brief and recent,
and subjects were asked to confirm the names of as many medications as possible
from containers. Thus, we believe that the data from the Slone Survey provide
an accurate picture of medication use in the US population.
In conclusion, our data document that in any given week, the large majority
of US adults take at least 1 prescription or OTC medication, and substantial
numbers take multiple products. Forty percent take at least 1 vitamin/mineral,
and 1 in 7 adults takes at least 1 herbal/supplement. One in 6 patients taking
prescription drugs is concurrently taking 1 or more herbals/supplements, which
poses potential risks of interactions. Identification of usage patterns for
the full range of medications, including the reasons for use, provides a basis
for improving safety and reducing risks associated with their consumption.