Prevalence and characteristics of opioid use in the US... : PAIN (original) (raw)
1. Introduction
Opioids are commonly administered for the treatment of moderate to severe pain and are among the most widely prescribed drugs in the United States [11]. Health policy makers, health professionals, and the general public have an interest in the provision of better pain therapies. In response to that interest, a strategy for more effective treatment of chronic pain was adopted in the 1990s [2,3], and weaker opioids such as codeine were largely replaced by more potent drugs, including oxycodone and methadone. While these drugs have an essential role in pain management, there are concerns about potential misuse. Recent reports have noted a linear relationship between opioid analgesic sales and the drug-poisoning mortality rate across the United States [18]; the acquisition of opioids through means such as theft, “doctor-shopping”, and the Internet has increased [8].
Despite these concerns, characteristics of opioid use within the non-institutionalized US population are not well-described in the literature, particularly in recent years. We therefore examined opioid use among US adults using data from a large, nationally-representative telephone survey.
2. Methods
From February 1998 through April 2007, the Slone Epidemiology Center of Boston University conducted a telephone survey of a random sample of residents of households in the 48 contiguous states and the District of Columbia [9]. Individuals not eligible for the survey included those without a land-line telephone, and those who resided in vacation homes for less than three consecutive months or in institutional settings, including nursing homes, group homes, military barracks, and prisons.
Subjects were identified by random-digit dialing (RDD) from a commercial source of telephone numbers prescreened to eliminate business exchanges [4]. At least 20 attempts were made to contact the targeted numbers before the number was considered unreachable. At each contacted number, one individual in the household was selected for interview by a computer-generated random number procedure.
Information was recorded on all prescription and non-prescription medications, vitamins/minerals, and herbals/supplements taken during the preceding 7 days. The subject was first asked to gather all relevant bottles or packages. Then, a list of reasons for use, including “pain/headache/backache” and “arthritis/joint pain”, was read to identify use of other medications that may not have been covered by the available bottles. Finally, the subject was asked if he/she had taken anything else not already mentioned. For each reported medication, information was obtained on 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.
Demographic information included age, sex, race, Hispanic origin, years of education, and income (in ranges); state of residence was provided with the sample of telephone numbers. Beginning in August 2005, a brief series of medical history questions was asked of all study subjects.
A comparison of the Survey population with the US population from Census 2000 [1] shows similarity with regard to race, region, Hispanic ethnicity, and age. As is typical of telephone-based RDD surveys, the Slone Survey population included more females (55% vs. 51%) and more college graduates (35% vs. 25%).
In this descriptive cross-sectional study, results are presented as prevalence of use in a one-week period. As used here, the term opioids includes both natural opiates and synthetic opioids, and both single ingredient and combination products. Regular opioid use is defined as use on at least 5 days per week for a duration of at least four continuous weeks. Age, sex, years of education, race, year of interview, and geographic region were examined as predictors of regular opioid use, using logistic regression to control all factors simultaneously. Prevalence estimates were weighted according to household size, a factor that is inversely related to the probability of selection within each household. In order to facilitate generalization of our results to the general population of non-institutionalized US adults, it was necessary to account for demographic differences between the survey sample and the US population. Therefore, prevalence estimates were further adjusted using age/sex/education weights derived from the US Census.
The analysis is based on 19,150 individuals aged 18 years or older interviewed from February 1998 through September 2006. The participation rate (AAPOR RR3) [23] during the course of the survey was 62%.
3. Results
As shown in Table 1, there were 926 subjects who used opioids during the previous week (adjusted prevalence, 4.9%); 406 subjects used opioids regularly (adjusted prevalence, 2.0%). Among the subjects who were classified as “other” opioid users (i.e., not regular), 142 had use of at least 4 weeks’ duration but fewer than 5 days per week, 104 had use on five or more days per week but of less than 4 weeks’ duration, and 274 satisfied neither condition. Among the regular users, 71 individuals (17%) took two opioids (47 of these used both drugs regularly) and seven took three opioids.
Opioid usea among 19,150 subjects, 1998–2006
Table 2 displays regular use of opioids according to strata of age, sex, education, and race. Multivariate analysis revealed differences in use for each of the factors: regular opioid use increased significantly with age and was higher in females than males; there was a significant inverse association with years of education; African Americans were significantly less likely to use opioids regularly than non-Hispanic whites. Prevalence estimates were then adjusted using weights derived from the US population. Opioids were used regularly by 0.7% of those younger than 40 and 3.4% in subjects aged 70 or older. The adjusted prevalence was 4.0% among subjects who had not completed a high school education; the estimate was 1.0% in college graduates. With respect to race/ethnicity, the estimates were 2.3%, 2.1%, and 1.5% in non-Hispanic whites, African Americans, and Hispanics, respectively. Regarding the four major US Census regions, the adjusted prevalence of regular opioid use was higher in the South Central region (2.4%) than in the Northeast and North Central census areas (Table 3). Regular opioid use generally increased over time, with an adjusted prevalence of 2.7% in 2005; the estimate was lower during the last 9 months of 2006, but the confidence interval overlapped the estimate for the previous year. Although the prevalence was 2.6% in 2000, the estimates ranged from 1.3% to 1.6% in the years before and after.
Regular opioid usea according to age, sex, education, and race
Regular opioid usea according to region and year of interview
Characteristics of use among the 406 regular opioid users are shown in Table 4. Twenty-one percent had taken opioids for less than 6 months, and almost half (47%) had taken them for two or more years. Nearly all use was in an oral form; patches were used by only 4% of regular opioid users. Among the drugs reported, combination products containing hydrocodone plus acetaminophen and propoxyphene plus acetaminophen were the first and third most commonly used. The most commonly used single ingredient products were tramadol and hydrocodone. As expected, pain dominated the reasons reported for opioid use (data not shown): 36% reported pain and did not specify a site, 20% specified back pain, 26% mentioned pain of another specific site or due to a specific cause (e.g., headache, fibromyalgia), 13% reported arthritis, and 5% mentioned a reason for use unrelated to pain (e.g., anxiety).
Characteristics of use among 406 regular opioid users
Concomitant use of non-opioid medications was evaluated according to opioid use The proportion of regular opioid users who took ten or more other medications (including vitamin and herbal supplements) was 21%, compared to 16% in non-regular opioid users and 4.5% in individuals who did not use opioids. The proportions who used five or more prescription drugs were 32%, 22%, and 7.5%, respectively (data not shown).
In order to gain further insight into the issue of polypharmacy, use of specific classes of non-opioid drugs was compared between regular opioid users and subjects who had not used opioids during the previous week; several drug classes are shown in Table 5. Included were other non-opioid drugs used in the treatment of pain (acetaminophen, aspirin, non-selective non-aspirin non-steroidal antiinflammatory drugs (NSAIDs), and COX-2 NSAIDs), drugs that may be used to treat potential side effects of opioid use (laxative/stool softeners, H2 blockers, and proton pump inhibitors), and drugs that may be otherwise associated with opioid use (antidepressants and anticonvulsants). With the exception of acetaminophen and aspirin, each of these drugs/classes was used more commonly by regular opioid users. The largest differences were observed for COX-2 NSAIDs (12% vs. 2.4%), laxatives (12% vs. 2.0%), proton pump inhibitors (21% vs. 5.1%), antidepressants (31% vs. 7.1%), and anticonvulsants (27% vs. 2.6%). When use of broad groupings of other non-opioid drugs was examined (data not shown), the prevalence was also higher in regular opioid users than non-users for many classes of drugs used for chronic conditions, such as ACE inhibitors for cardiovascular disease (16% vs. 7%), and insulin for diabetes (6% vs. 2%).
Concomitant drug use among 406 regular opioid users and 18,224 non-users
4. Discussion
Results from this nationally based telephone survey of medication use show that in any given week during the period February 1998 through September 2006, approximately 5% of US adults took an opioid. The prevalence of regular opioid use (at least 5 days per week for at least 4 weeks) was 2%, which translates to 4.3 million individuals nationwide. Regular opioid use increased with age and decreased with increasing years of education: the highest stratum-specific prevalence was 4.0% among subjects who had not graduated high school. There was a significant increase in use over time. The adjustment using weights derived from the age/sex/education distribution of the US population (Census 2000) generally produced prevalence estimates that were similar to those that were unadjusted. One exception was the prevalence for African Americans, where an under-representation of subjects with fewer years of education resulted in a considerably higher adjusted estimate.
Nearly half of regular opioid users had been taking them for at least 2 years and nearly 20% for 5 years or more. Polypharmacy was also a characteristic of regular opioid users, one-third of whom took at least five non-opioid prescription drugs concurrently, compared with less than one-tenth of non-users. Somewhat surprisingly, a higher prevalence of use of non-narcotic analgesics was not observed; there was, however, more use of non-selective NSAIDs and COX-2 NSAIDs. There was also more use of drugs that may treat side effects associated with regular opioid use, such as constipation and gastrointestinal discomfort. Although we observed a higher prevalence among regular opioid users of two classes of drugs sometimes associated with pain treatment, anticonvulsants and antidepressants, we were not able to determine the temporal sequence. A higher prevalence of use of some drugs for chronic conditions, such as heart disease and diabetes, suggests that regular opioid users have more health problems than non-users.
Previous reports of the prevalence of opioid use vary somewhat, perhaps because of differences in the study populations or how use was measured or defined, but the findings are broadly similar to those reported here. There have been four studies of the general US population. Three studies (National Health and Nutrition Examination Survey III [NHANES], 1988–1994; Health Care for Communities, 1997–1998; Health Care for Communities, 1998 and 2001) measured opioid use by individuals and reported prevalences ranging from 3.0% to 3.5% [17,21,22]. Two of the studies measured opioid use of several times a week for at least a month in the past 12 months [21,22], and the third identified opioid usage in the past month [17]. The somewhat broader exposure definitions may account for the higher prevalence estimates than were observed in the current study. The fourth study, using data from the National Ambulatory Medical Care Survey (NAMCS) [15], reported that opioid prescriptions increased from 4.1% (in 1992 and 1993) to 6.3% (1998 and 1999) of office visits to primary care providers. Among the four studies, predictors for opioid use included: female sex, older age, receiving an NSAID, having a mental health disorder, problem drug use, back problems, and other chronic pain. The most frequently used opioids in the NHANES survey were mild analgesics, including codeine phosphate with acetaminophen (28%), propoxyphene with acetaminophen (24%), hydrocodone bitartrate with acetaminophen (16%), and propoxyphene (9.5%). The observation that codeine is one of the less commonly used opioids in the current study could be explained by the trend toward using stronger opioids in the years since NHANES II. Similar to our findings, the NAMCS study [15] reported that the most common diagnoses for which an opioid was prescribed included back pain (29%), musculoskeletal conditions (18%), and headache (11%).
Our results are also comparable to two population-based studies in Northern Europe. A study of home-dwelling individuals in Helsinki, Finland, from 1989–1999 [19] reported a 2.8% prevalence of at least weekly opioid use, which increased with age. A population-based study from Denmark [7] reported a 3% prevalence of use of opioids “regularly or continuously” in 2000. Predictors of use included older age, less education, and negative perceived health.
Not surprisingly, prevalence estimates for selected subsets of the US population have been higher than for the general population. In a nationwide household survey of the US population with back pain [12], the prevalence of opioid use ranged from 11% to 13% over the years 1996 through 1999. In a study of individuals treated for musculoskeletal pain [5], the proportion of office visits during which an opioid was prescribed ranged from 8% to 11% for acute pain and 8% to 16% for chronic pain in samples from 1980–1981 to 1999–2000. Two small hospital-based studies from the Veterans Affairs health care system reported the highest US prevalence figures. The first, conducted in 1997 in a Minnesota Orthopedic Spine Clinic, found that 66% of patients were prescribed opioids [13]. This study followed the opioid users and found that more than 75% took them for less than 1 year. The other study observed that 44% of patients received opioid prescriptions at the Veterans Affairs Palo Alto Health Care System in 2000 [6].
Most of the prevalence estimates presented here were based on reasonably large numbers of users and had relatively narrow confidence limits. Two potential sources of error in the Slone Survey data are selection bias and information bias. Although the Slone Survey participation rate of 62% is relatively high for an RDD survey [16], the participants could differ from non-participants with regard to medication use. Compared to the US Census, our population had a larger proportion of female subjects and a higher level of education. These disparities are typical of RDD surveys [20] and may reflect both a decreased propensity to participate by certain individuals and a restriction of the survey population to households with a land-line telephone. Individuals who rely on cellular telephones, and are thus not included in our survey, are disproportionately male, young, and living in urban areas [10]. Although we adjusted overall prevalence estimates for differences in age, sex, and education to the distribution of these factors in the US population [1], the possibility of selection bias could not be ruled out.
With regard to information bias, several strategies were employed to minimize error due to differential reporting of the use of specific products. We thoroughly trained the study interviewers to conduct the interviews in a consistent manner, we inquired about a brief and recent exposure period, we employed several methods of inquiry regarding medication use, and we confirmed as many medication names as possible from containers. Some degree of underreporting is likely in studies of opioid use due to the sensitive nature of the topic and the possibility that the drugs are sometimes obtained illegally. The anonymity of an RDD telephone interview may reduce underreporting, but probably does not eliminate it. Thus, it is reasonable to assume that our prevalence estimates provide a conservative approximation of the scope of exposure to opioids in this country. Within these limitations, we believe the Slone Survey data can be extrapolated to the non-institutionalized US population.
In conclusion, this study, conducted on a representative sample of the US adult population, indicates that in a given week, over ten million Americans are taking opioids, and more than four million are taking them regularly (i.e., at least 5 days per week for at least 4 weeks). Among regular users, almost half have been taking opioids for 2 or more years. Polypharmacy is common in opioid users, many of whom are using other analgesics, antidepressants, and drugs used to treat chronic medical conditions. Given the large number of individuals affected, the recent increase in public health concern for safe and effective pain management is appropriate. One in four US adults reported an episode of pain during the last month that persisted for more than 24h, and one in ten reported pain that lasted a year or more [14]; this proportion is likely to increase as the population ages. The National Pain Care Policy Act of 2005, currently under consideration by a US House of Representatives subcommittee, recommends increased research into pain management, development of strategies to advance the quality, appropriateness and effectiveness of pain care, and a national educational campaign to inform the public on responsible pain management. The extent and characteristics of opioid use among US adults reflected in the Slone Survey reinforce the need to strike a rational balance between opioid misuse and effective control of chronic pain.
Acknowledgements
The authors appreciate the contributions of Marie Berarducci and Marilyn Wasti, study supervisors; Gene Sun, information systems; and the interviewing staff. Data collection was supported by internal Slone Epidemiology Center funds and data analysis was supported by GlaxoSmithKline.
References
[1] 2000 Census of Population and Housing. Summary social, economic, and housing characteristics. Washington, DC: U.S. Department of Commerce, Economics and Statistics Administration, Bureau of the Census; 2000. Available from: http://factfinder.census.gov [Accessed 12/12/06].
[2] American Academy of Pain Medicine, American Pain Society. The use of opioids for the treatment of chronic pain: a consensus statement from the American Academy of Pain Medicine and the American Pain Society. Clin J Pain. 1997;13:6-8.
[3] American Society of Anesthesiologists. Practice guidelines for chronic pain management: a report of the American Society of Anesthesiologists Task Force on Pain Management, Chronic Pain Section. Anesthesiology. 1997;86:995-1004.
[4] Brick JM, Waksberg J, Kulp D, Starer A. Bias in list-assisted telephone samples. Public Opin Q. 1995;59:218-235.
[5] Caudill-Slosberg MA, Schwartz LM, Woloshin S. Office visits and analgesic prescriptions for musculoskeletal pain in US: 1980 vs. 2000. Pain. 2004;109:514-519.
[6] Clark JD. Chronic pain prevalence and analgesic prescribing in a general medical population. J Pain Symptom Manage. 2002;23:131-137.
[7] Eriksen J, Sjøgren P, Bruera E, Ekholm O, Rasmussen NK. Critical issues on opioids in chronic non-cancer pain: an epidemiological study. Pain. 2006;125:172-179.
[8] Forman RF, Woody GE, McLellan T, Lynch KG. The availability of web sites offering to sell opioid medications without prescriptions. Am J Psychiatry. 2006;163:1233-1238.
[9] 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;287:337-344.
[10] Keeter S, Kennedy C, Tompson T, Mokrzycki M, Clark A. What’s Missing from National RDD Surveys? The Impact of the Growing Cell-Only Population (abstract). Presented at the 62nd Annual Conference of the American Association for Public Opinion Research. Anaheim, CA; May 17, 2007.
[11] Kuehn BM. Opioid prescriptions soar. JAMA. 2007;297:249-251.
[12] Luo X, Pietrobon R, Hey L. Patterns and trends in opioid use among individuals with back pain in the United States. Spine. 2004;29:884-890. [discussion 891].
[13] Mahowald ML, Singh JA, Majeski P. Opioid use by patients in an orthopedics spine clinic. Arthritis Rheum. 2005;52:312-321.
[14] National Center for Health Statistics. Health, United States, 2006 with chartbook on trends in the Health of Americans. Hyattsville, MD: National Center for Health Statistics; p. 68–71. Available from: http://www.cdc.gov/nchs/hus.htm [Accessed 06/06/07].
[15] Olsen Y, Daumit GL, Ford DE. Opioid prescriptions by US primary care physicians from 1992 to 2001. J Pain. 2006;7:225-235.
[16] O’Rourke D, Johnson T. An inquiry into declining RDD response rates. Part III: a multivariate review. Surv Res. 1999;2:1-3.
[17] Paulose-Ram R, Hirsch R, Dillon C, Losonczy K, Cooper M, Ostchega Y. Prescription and non-prescription analgesic use among the US adult population: results from the third National Health and Nutrition Examination Survey (NHANES III). Pharmacoepidemiol Drug Saf. 2003;12:315-326.
[18] Paulozzi LJ, Ryan GW. Opioid analgesics and rates of fatal drug poisoning in the United States. Am J Prev Med. 2006;31:506-511.
[19] Pitkala KH, Strandberg TE, Tilvis RS. Management of nonmalignant pain in home-dwelling older people: a population-based survey. J Am Geriatr Soc. 2002;50:1861-1865.
[20] Smith TW. The hidden 25 percent: an analysis of nonresponse on the 1980 general social survey. Public Opin Q. 1983;47:386-404.
[21] Sullivan MD, Edlund MJ, Steffick D, Unutzer J. Regular use of prescribed opioids: association with common psychiatric disorders. Pain. 2005;119:95-103. [Epub 2005 Nov 17. Dec 15].
[22] Sullivan MD, Edlund MJ, Zhang L, Unützer J, Wells KB. Association between mental health disorders, problem drug use, and regular prescription opioid use. Arch Intern Med. 2006;166:2087-2093.
[23] The American Association for Public Opinion Research. 2004. Standard definitions: final dispositions of case codes and outcome rates for surveys, 3rd ed. AAPOR, Lenexa, KS.
Keywords:
Opioids; Survey; Prevalence; Epidemiology; Population-based
© 2008 Lippincott Williams & Wilkins, Inc.