Aim To compare predictors of smoking initiation in two longitudinal studies in California conducted during periods when adolescent smoking prevalence was increasing (1993-96) and decreasing (1996-99). Design, setting and participants Cohorts of 12-15 -year-old never smokers were identified from the cross-sectional 1993 and 1996 California Tobacco Surveys (large population-based telephone surveys) and followed-up 3 years later (1993-96, n = 1764; 1996-99, n = 2119). Measures We compared cohort transition rates to any smoking by follow-up in risk groups defined by known predictors of smoking initiation at baseline. risk groups were defined using a mulBesides examining predictors individually, tivariate analysis. Findings Overall, transition to any smoking by follow-up occurred in 38.3 +/- 4.00% (% +/- 95% confidence interval) of never smokers in the 1993-96 cohort and 31.1 +/- 2.6%, in the 1996-99 cohort. For most predictors, the transition rate for adolescents with the characteristic was the same or only slightly lower in the 1996-99 cohort compared to the 1993-96 cohort, but the transition rate in those without the characteristic was generally much lower, thus increasing the power of the predictor. The multivariate analysis confirmed that compared to the 1993-96 cohort, transition occurred much less often in the 1996-99 cohort for adolescents at low rather than at medium or high risk of future smoking. Conclusions The turnaround in California adolescent smoking in the mid-1990s, when smoking began to decline, appears to come primarily from adolescents already at low risk of future smoking (as defined by a variety of predictors), who transitioned to smoking at much lower rates than previously.

Background: It is not clear whether the decline in African American adolescent smoking in the 1980s reflected a delay in age of onset of regular smoking initiation rather than success in preventing initiation completely. Purpose: The purpose of this study is to identify whether the marked reductions in African American adolescent smoking in the 1980s were offset by increased initiation in young adults. Methods: We combined data from the Tobacco Use Supplements of the 1992-1993, 1995-1996, and 1998-1999 Current Population Surveys (n = 512,258), and reconstructed year of smoking initiation and calculated age-specific incidence of initiation from 1970 to 1992. We then compared detailed age-specific rates of initiation for two 5-year periods selected to be before and after the documented large declines in African American adolescent smoking. Results: In the time period after marked declines in African American adolescent smoking (1987-1991), the incidence of initiation of regular smoking decreased for African Americans ages 14 to 16 and increased for ages 18 to 20. Such a delay was not as evident among non-Hispanic Whites. The delay that was slight in regular smoking initiation among African Americans relative to non-Hispanic Whites in 1975-79 had increased substantially by 1987-91. Conclusions: Reductions in African American adolescent smoking in the 1980s were offset by increased initiation among young adults ages 18 to 20 during this time period and suggest that the window for uptake of regular smoking shifted to older ages for African Americans more so than non-Hispanic Whites. Efforts to combat smoking should remain aggressive into young adulthood, when the tobacco industry's efforts to gain new smokers intensify.