Logistic regression coefficients and their 95% confidence intervals (95% CIs) were exponentiated to create odds-ratios (ORs) and their 95% CIs. The latter are presented here because they are easier to interpret than logistic regression coefficients. The term “gross effects” of baseline smoking and nicotine dependence is used to refer to associations based on prediction equations that controlled only for baseline socio-demographics and baseline history of SROs. The term “net effects,” in comparison, is used to refer to associations based on prediction equations that additionally controlled for the full set of baseline risk factors enumerated above. Continuous predictors were divided into categories to minimize the effects of extreme values, while some categories of predictors were combined to stabilize associations when the OR did not differ meaningfully across contiguous categories. Standard errors and significance tests were estimated using the Taylor series method42 implemented in the SUDAAN software system43 to adjust for NCS and NCS-2 design effects. Multivariate significance was evaluated using Wald χ2 tests based on design-corrected coefficient variance-covariance matrices. Statistical significance was evaluated using two-tailed .05-level tests.
