Substance Abuse by Older Adults:  Estimates of Future Impact on the Treatment System

Chapter 4. Age Differences in Multiple Drug Use: National Admissions to Publicly Funded Substance Abuse Treatment

Leigh A. Henderson,* Ph.D.

The purpose of this chapter is to examine the use of multiple drugs (polydrug use) by age in national admissions to publicly funded substance abuse treatment with special focus on adults aged 55 or older. The Treatment Episode Data Set (TEDS), a national dataset of admissions to publicly funded substance abuse treatment (Office of Applied Studies [OAS], 2001), includes a substantial number of older adults and permits examination of the number and types of substances used by this population, their source of referral to treatment, and their prior experience with the substance abuse treatment system.

Polydrug use is a concern because of the potential for additive or interactive effects of the drugs. These may produce different and perhaps more severe adverse consequences. For example, in drug-related deaths reported to medical examiners in 41 metropolitan areas in 1998, an average of 2.5 drugs was found (OAS, 2000). The recent proliferation of prescription psychoactive drugs, and their aggressive marketing, has added significantly to the potential for polydrug use (National Institute for Health Care Management, 2001). Alcohol, illicit drugs, and prescription drugs diverted to the illicit marketplace have been the traditional sources of polydrug use. To these problems is now added the potential for misuse (intentional or unintentional) of one or more drugs prescribed by a medical practitioner. Polydrug use is of particular concern among older adults, where one study estimated that 30 percent of persons over 65 take eight or more prescription drugs daily (Sheahan, Hendricks, & Coons, 1989). Many of these drugs may be psychoactive, taken for sleep disorders, chronic pain, or mood disorders (Center for Substance Abuse Treatment [CSAT], 1998).

Although the problems engendered by polydrug use are drawing increasing attention, indicators of its prevalence nationally and of specific drug combinations are lacking, particularly among older adults. In part, this is because polydrug use has been seen as an illicit drug problem. Research in a longitudinal cohort has indicated that initiation of illicit drug use after age 28-29 is extremely rare (Chen & Kandel, 1995). By age 28-29, some 85 to 95 percent of users of drugs other than alcohol and marijuana had stopped their use (Raveis & Kandel, 1987). However, initiation of use of prescription psychoactives was an exception, and the cohort has not yet been followed beyond the age of 35. Among older adults, prescription polydrug use is more likely to be a problem than is illicit polydrug use.

In the general population, existing studies indicate that polydrug use is fairly widespread among adolescents and young adults. A community-based sample of persons aged 28 to 32 found that 31 percent used marijuana and alcohol, 28 percent used alcohol and illicit drugs other than marijuana, and 22 percent used marijuana and other illicit drugs (Earleywine & Newcomb, 1997). A study among 12^th graders found that 29 percent reported simultaneous polydrug use (the use of two or more substances in combination) during the past year (Collins, Ellickson, & Bell, 1998).

Polydrug use has been demonstrated to be common among injection drug users and persons in correctional facilities. A study of injection drug users found that an average of 5.3 of 8 drug classes had been used in the 6 months prior to interview (Darke & Ross, 1997). Similarly, a study of heroin injectors and amphetamine users found that averages of 5.2 and 6.3 of 8 drug classes, respectively, had been used in the past 6 months (Darke & Hall, 1995). In a sample of injection drug users aged 16 to 45, 34 percent had used one substance in addition to their primary substance, 34 percent had used two, 19 percent had used three, and 13 percent had used four or more additional drugs (Klee, Faugier, Hayes, Boulton, & Morris, 1990). Among prison inmates, half reported using 5 or more of a list of 14 drugs (including alcohol), and 20 percent had tried 8 or more (Kassebaum & Chandler, 1994).

In substance abuse treatment populations, polydrug use has been studied primarily among alcoholics. National treatment population data indicate that use of alcohol and drugs is more common than use of either alone (Martin et al., 1996a). In a study of 212 persons in inpatient treatment for alcoholism (age range from 19 to 63, average 36.4), 61 percent reported current use of other drugs (Jensen, Cowley, & Walker, 1990). An average of 2.3 different combinations were reported. Among males in alcoholism treatment (age range from 20 to 68, average 42), an average of 3 drugs in addition to alcohol were found to have been abused (Martin, Kaczynski, Maisto, & Tarter, 1996b). In a study combining treatment and community populations of adolescents (average age 16.7), those with an alcohol dependence diagnosis had used an average 3.8 of 5 illicit drug classes, those with an alcohol abuse diagnosis had used an average of 3.0 illicit drugs, and those with no alcohol diagnosis had used an average of 1.9 drug classes (Belding, Iguchi, Lamb, Lakin, & Terry, 1995). The majority of subjects in each group had used illicit drugs (from 81 to 98 percent). Polydrug use in methadone maintenance is widely acknowledged (Iguchi, Stitzer, Bigelow, & Liebson, 1988; OAS, 1999), but published quantitative reports are rare.

Although studies have documented polydrug use in various populations, most have been limited in scope, focusing on a particular population (e.g., persons in alcohol treatment, injection drug users, adolescents). In this study, we examine polydrug use by 5-year age group as reported in TEDS, a record-based national data collection system for admissions to publicly funded substance abuse treatment. The substances inventoried in TEDS include alcohol and illicit drugs, as well as prescription drugs when they have caused dependence requiring treatment. This analysis will provide a benchmark against which changes in polydrug use in the treatment system can be measured. As the focus of this report is the baby boom generation born between 1946 and 1964, and what demands they may make on health care resources in the future, emphasis is placed in the analysis on this generation and on current older users of the treatment system. Prior experience with the treatment system and source of referral to treatment are included, as these may affect use of the system.

Description of the Dataset

TEDS is maintained by OAS in the Substance Abuse and Mental Health Services Administration (SAMHSA). The TEDS system includes records for some 1.5 million substance abuse treatment admissions annually. TEDS comprises data that are routinely collected by States in monitoring their individual substance abuse treatment systems. It does not include data on facilities operated by Federal agencies (the Bureau of Prisons, the Department of Defense, and the Veterans Administration). Selected data items from the individual State data files are converted to a standardized format consistent across States, and these standardized data constitute TEDS. TEDS consists of a Minimum Data Set collected by nearly all States, and a Supplemental Data Set collected by some States. The Minimum Data Set consists of 19 items that include demographic information; primary, secondary, and tertiary substances of abuse and their route of administration, frequency of use, and age at first use; source of referral to treatment; number of prior treatment episodes; and service type, including planned use of methadone. The Supplemental Data Set consists of 15 items that include psychiatric, social, and economic measures.

Study Population

This study is a cross-sectional analysis of 1,493,710 admissions reported to TEDS for 1997. Admissions represent treatment episodes during the year rather than the number of individuals seeking treatment. A person who entered residential treatment in February, transferred from residential to outpatient treatment in March, and completed outpatient treatment in April, but then reentered treatment in November, would be counted as having had two treatment episodes and thus two admissions. The transfer from residential to outpatient treatment is considered a continuation of the same episode and not a new admission. The report excludes 402 admissions who were younger than 10 years old.

Analysis

For this analysis, both licit and illicit substances were classified according to the system used throughout this monograph. The following substance classes were used:

• Alcohol: alcohol;
• Stimulants: cocaine, methamphetamine, amphetamine, and other stimulants;
• Opiates: heroin, nonprescription methadone use, and other opiates and synthetics with morphine-like effects;
• Cannabinoids: marijuana, hashish, THC, and other cannabis sativa preparations;
• Hallucinogens: phencyclidine (PCP) and other hallucinogens (LSD, DMT, STP, mescaline, psilocybin, etc.);
• Tranquilizers: benzodiazepines and non-benzodiazepine tranquilizers;
• Sedative/hypnotics: barbiturates and non-barbiturate sedatives and hypnotics;
• Inhalants: ether, glue, chloroform, nitrous oxide, gasoline, paint thinner, etc.;
• Over-the-counter: aspirin, cough syrup, sleep aids, and other legally obtained nonprescription medications; and
• Other: other or unspecified substance.

All data are reported by 5-year age group, the standard reference for the chapters in this report. The maximum age that the TEDS system could accommodate at the time of data entry was 96. In the tables and Figure 1, the age groups that include the baby boom generation (aged 33 to 51 in 1997) are highlighted.

Results

Figure 1 shows the distribution by age of the 1997 TEDS admissions: 97 percent were younger than 55 in 1997, 2 percent were aged 55 to 64, and less than 1 percent were 65 or older. Only 118 were over 89 years of age. The greatest number of admissions were for ages 30 to 39; numbers were significantly lower for each subsequent age group. The baby boom generation made up 48 percent of all those entering treatment in 1997, when they were aged 33 to 51.

Table  1 shows the primary substance class, by age in 1997, reported at admission to treatment. Four substance classes accounted for 99 percent of all admissions. These were alcohol (50 percent), stimulants (20 percent), opiates (16 percent), and cannabinoids (13 percent). In no age group did other substances combined account for more than 4 percent of admissions. The proportion of admissions for primary alcohol abuse increased for each age group through age 74 (from 28 percent of those aged 10 to 14 to 89 percent of those aged 70 to 74), and then declined. Admissions for primary use of other substances peaked at ages 10 to 14 for cannabinoids, ages 25 to 34 for stimulants, and ages 40 to 49 for opiates. The proportions of admissions for tranquilizers and sedatives were greatest among those aged 75 or older.

Figure 1 TEDS Admissions: 1997 Age Distribution

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Note: Data for age groups that include the baby boom generation (aged 33 to 51 in 1997) are highlighted.

Source: SAMHSA, Office of Applied Studies, Treatment Episode Data Set (TEDS), April 16, 2001.

Table s  1a and 1b show the same information as in Table  1, but for males and females separately. Men were more likely to be in treatment for alcohol at all but the youngest ages. Women were more likely to be in treatment for "hard" drugs, such as opiates and stimulants.

Table  2 shows the distribution by age of any use of a substance, either as primary, secondary, or tertiary. The average number of substance classes reported was 1.8 to 1.9 through age 39. This declined with age to 1.1 at ages 65 to 79, but rose again in each subsequent age group, to 1.8 at ages 95 to 96. Abuse of alcohol, either alone or as a secondary substance, was characteristic of most treatment admissions. Overall, 73 percent of all admissions used alcohol, 41 percent used stimulants, 36 percent used cannabinoids, and 19 percent used opiates. Use of alcohol was reported by at least 69 percent of all admissions in each age group, and it tended to increase with age, peaking at 92 percent of admissions aged 70 to 74. Use of alcohol declined after age 85 to 71 percent among those 90 or older.

Use of substances other than alcohol reflected the underlying primary substance patterns. Peak use occurred at different ages for different substances, declined for subsequent age groups, but rose again among those aged 75 or older. Stimulant use increased from 13 percent of those aged 10 to 14 to over half of those aged 30 to 34. Use of marijuana was highest among the youngest age groups—85 percent of those aged 10 to 14 and 80 percent of those aged 15 to 19. Use of opiates increased from 1 percent of those aged 10 to 14 to 28 percent of those aged 45 to 49.

Figure 2 and Table  3 depict polydrug use and polydrug combinations by age group. Overall, 44 percent of treatment admissions reported use of a single substance class, 36 percent reported use of two substance classes, and 20 percent reported use of three substance classes. The number and combination of substances used varied greatly by age. Generally, the likelihood of using a single substance class increased with age to ages 70 to 74. For persons aged 75 or older, the likelihood of using two or three substance classes increased with each age group. Among those reporting single substance classes, alcohol was the most common in all age groups except those younger than 20, where marijuana predominated. Among two-drug combinations, alcohol and marijuana were most common for those younger than 25. For those aged 25 or older, the most frequent combination was alcohol and stimulants. Among three-drug combinations, alcohol, stimulants, and marijuana were most common for all age groups except the youngest (ages 10 to 14), where alcohol, marijuana, and other drugs (primarily hallucinogens) predominated.

Table  4 shows the distribution by age of the number of prior treatment episodes. Overall, 42 percent of admissions were entering treatment for the first time. The proportion was high among the younger age groups, then declined to 33 percent of those aged 40 to 49. Among those aged 45 or older, the proportion of those entering treatment for the first time increased steadily until age 85.

Table  5 shows the distribution by age of the source of referral to treatment. Overall, 35 percent of admissions were referred through the criminal justice system, 33 percent through individual or self-referral, 13 percent from other substance abuse treatment providers, and 7 percent through other health care providers. The criminal justice system was the most frequent source of referral to treatment for persons younger than 30 and for those aged 65 to 74. Individual or self-referral was responsible for the largest proportion of admissions for those aged 30 to 65 and for those 75 or older. Schools referred substantial proportions of those under 20 to treatment, but employee assistance programs (EAPs) contributed little to treatment entry in these publicly funded facilities. The proportion referred to substance abuse treatment through health care providers increased steadily from 6 percent at ages 15 to 19 to 19 percent at ages 75 to 79. Health care providers were the third leading source of treatment referral for persons aged 60 to 89.

Figure 2 Polydrug Use, by Age Group

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Source: SAMHSA, Office of Applied Studies, Treatment Episode Data Set (TEDS), April 16, 2001.