LAUSR

AIM To test whether intrapersonal growth in e-cigarette advertising exposure over time is associated with growth in e-cigarette use and/or cigarette smoking. DESIGN Longitudinal study using four waves of data were collected in 6-month intervals between 2018-2020. SETTING AND PARTICIPANTS Participants were 2327 young adults recruited from colleges in Hawaii, U.S.A. MEASUREMENTS Data were collected on demographics, e-cigarette advertising exposure measured using the cued recall method, and recent (past-30-day) cigarette and e-cigarette use. FINDINGS The average trajectory for e-cigarette advertising exposure over time was significant and upward [M slope = 0.18 (0.14-0.22), P < 0.0001]. However, average trajectories for e-cigarette [M slope = -0.08 (-0.18-0.02), P = 0.09] and cigarette [M slope = -0.14 (-0.30-0.02), P = 0.07] use were not. There were significant differences in individual level trajectories across participants for advertising exposure [σ2 = 0.12 (0.10-0.14), P < 0.0001], e-cigarette use [σ2 = 0.22 (0.14-0.30), and cigarette smoking (σ2 = 0.17 (0.09-0.25), P < 0.0001). Individuals with increasing rate of advertising exposure showed increasing rate of e-cigarette use [B = 0.63 (0.36-0.90), P < 0.0001). Neither initial level of, nor rate of change in, advertising exposure was significantly associated with cigarette smoking growth factors (P > 0.05). Higher initial level of e-cigarette use was associated with higher initial level of cigarette smoking [B = 0.89 (0.69-1.09), P < 0.0001] but decreased rate of cigarette smoking over time [B = -0.12 (-0.20 - -0.04) P = 0.003]. Rate of change in e-cigarette use was not associated with the rate of change in cigarette smoking (P > 0.05). CONCLUSIONS Increased exposure to e-cigarette advertising appears to be associated with increased e-cigarette use but not with increased cigarette smoking. Higher initial level of e-cigarette use appears to be associated with higher initial level of cigarette smoking but may be associated with a decreasing rate of cigarette smoking over time.