Patterns of drug use, risky behavior, and health status among persons who inject drugs in San Diego, California

Background: Among persons who inject drugs (PWID) polydrug use has important health consequences. Specific drug combinations and drug use practices are highly dependent upon local drug markets.  Relatively little is known about polydrug use in San Diego where black tar heroin and methamphetamine dominate.

Methods: This study analyzed baseline data from an ongoing cohort study of PWID.  Latent class analysis (LCA) was used to identify patterns of weekly polydrug use (heroin, methamphetamine, prescription drugs, alcohol, and marijuana) via multiple routes of administration (injection, smoking, and swallowing). Logistic regression was used to identify demographic characteristics, HIV risk behaviors, and health outcomes associated with class membership.

Results:  The sample included 511 mostly white (51.5%) males (73.8%), with mean age of 43.5 years. Two distinct classes of drug users predominated: methamphetamine by multiple routes (51%) and heroin by injection (49%). In multivariable logistic regression analysis, class membership was associated with age, race, and housing status.  PWID who were HIV-seropositive and reported prior sexually transmitted infections had increased odds of belonging to the methamphetamine class. Those who were HCV-positive and reported previous opioid overdose had an increased odds of being in the primarily heroin injection class (all p-values <0.05).  

Conclusions:  LCA provides a parsimonious depiction of the interplay between drug use class, engagement in risky behavior, and adverse health outcomes.  This approach allowed us to identify sub-populations of illicit drug use and related risk behaviors. This information has implications for tailored interventions to prevent infectious disease and overdose among PWID.