DRUG SMOKING, PNEUMOCYSTIS-CARINII PNEUMONIA, AND IMMUNOSUPPRESSION INCREASE RISK OF BACTERIAL PNEUMONIA IN HUMAN IMMUNODEFICIENCY VIRUS-SEROPOSITIVE INJECTION-DRUG USERS

To examine the risk factors for the first episode of bacterial pneumon ia among human immunodeficiency virus (HIV)-seropositive injection dru g users (IDUs), medical record review was performed on IDUs participat ing in a cohort study from January 1988 to June 30, 1992. HIV-seroposi tive IDUs with a first episode of bacterial pneumonia (n = 40) were ma tched with up to five HIV-seropositive control subjects without bacter ial pneumonia(n = 197) by date of entry (+/-3 mo) and length of follow -up. Odds ratios (OR) were estimated using conditional logistic regres sion. The incidence of bacterial pneumonia was 1.93 in 100 person-year s in HIV seropositive and 0.45 in 100 person-years in HIV seronegative subjects (relative incidence = 4.3; 95% Cl 2.4 to 7.5). In univariate analyses, CD4 lymphocyte count < 200 cells/mu l previous episode of P neumocystis carinii pneumonia (PCP), age between 30 and 40 yr and smok ing illicit drugs (marijuana, cocaine, or crack) were associated with bacterial pneumonia. Cigarette smoking was associated with an increase d odds of bacterial pneumonia (OR = 2.0), but this was not statistical ly significant because it was nearly universal in this cohort. In mult ivariate analysis, CD4 < 200 cells/mu l (OR = 6.75, 95% Cl 2.13 to 21. 42) and smoking illicit drugs (OR = 2.24, 95% Cl 1.03 to 4.89) remaine d significantly associated with bacterial pneumonia. The odds ratio fo r cigarette smoking in the final model remained at 2.08 but was still not significant (95% Cl 0.49 to 8.70). Smoking illicit drugs had the s trongest effect on risk of bacterial pneumonia among HIV-seropositive IDUs with a previous history of PCP(OR = 22.94; 95% Cl 2.18 to 241.10) .