Injection drug users in the United States, 1979-2002: an aging population.

BACKGROUND: Injection drug use (IDU) is important in the epidemiology of blood-borne pathogens. Herein, trends in IDU from 1979 to 2002 are analyzed.
METHODS: The National Household Survey on Drug Abuse is an ongoing survey of drug use among the US population 12 years and older. Participants were chosen using a multistage sampling design and interviewed by written questionnaire (1979-1998) or audio computer-assisted self-interviewing (1999-2002). Herein, we examine the prevalence of a history of IDU at any time in the past (IDU-ever) or within the past year.
RESULTS: In the 2000-2002 surveys, 1.5% (95% confidence interval [CI], 1.4%-1.6%) reported IDU-ever (weighted estimate, 3.4 million persons). Prevalence was highest in persons aged 35 to 49 years (3.1%; 95% CI, 2.8%-3.4%), was higher in men (2.0%; 95% CI, 1.8%-2.2%) than women (1.0%; 95% CI, 0.9%-1.1%), and was higher in whites (1.7%; 95% CI, 1.5%-1.8%) than blacks (0.8%; 95% CI, 0.7%-1.1%) or Hispanics (1.1%; 95% CI, 0.8%-1.4%). Prevalence decreased with increasing annual income and educational level. Of all participants, 0.19% (95% CI, 0.16%-0.23%) reported IDU within the past year (weighted estimate, 440 000 persons). Ten years earlier (1990-1992), 1.6% (95% CI, 1.5%-1.8%) reported IDU-ever; prevalence did not differ by race. From 1979 through 2002, the mean age of participants with IDU within the past year increased from 21 to 36 years; the age of participants with IDU-ever increased from 26 to 42 years. From 2000 to 2002, 59.4% of all persons with IDU-ever were aged 35 to 49 years.
CONCLUSIONS: The mean age of injection drug users has increased substantially. Persons born between the late 1940s and early 1960s have the highest prevalence of IDU-ever. Self-reported IDU rates are now lower among young blacks than young whites.