TY - JOUR T1 - The chicken or the egg? The value of longitudinal research in an increasingly diverse tobacco product landscape JF - Tobacco Control JO - Tob Control SP - s131 LP - s133 DO - 10.1136/tobaccocontrol-2020-055694 VL - 29 IS - Suppl 3 AU - Brian A King Y1 - 2020/05/01 UR - http://tobaccocontrol.bmj.com/content/29/Suppl_3/s131.abstract N2 - The considerable progress made in reducing cigarette smoking is among the greatest public health achievements of the past century.1 In the U.S., current cigarette smoking prevalence among adults declined from nearly 43% in 1965 to approximately 14% in 2018.2 3 Moreover, current cigarette smoking prevalence among high school students has been steadily declining since the 1998 Master Settlement Agreement, from more than 30% in 2000 to approximately 8% in 2018.4 5 However, in the U.S. and globally, the tobacco product landscape has diversified in recent years to include a variety of combustible, non-combustible, and electronic products. Approximately 70% of U.S. adults who currently use tobacco products are cigarette smokers.3 In contrast, among current tobacco product users, less than half of young adults 18–24 years old (45.6%) and less than one-third of high school students (29.2%) are cigarette smokers (figure 1), with an increasing proportion of youth and young adults using novel tobacco products such as e-cigarettes.3 5 The increasing diversification of the tobacco product landscape has implications for efforts to understand how tobacco product use changes over time, including transitions within and between product types. Longitudinal data sources are particularly useful for assessing transitions between tobacco product types. In contrast to repeated cross-sectional surveys that are traditionally used for surveillance of changes in tobacco product use at the national and subnational levels, longitudinal studies afford the ability to document the temporal order of events, thus helping to answer the proverbial question, which came first, the chicken or the egg?’.Figure 1 Current cigarette and non-cigarette tobacco product use among US adults, young adults, and high school students, 2018. Source: National Health Interview Survey (current use defined as: ‘everyday’ or ‘someday’); National Youth Tobacco Survey (current use defined as: ≥1 day in past 30 days).This supplement to … ER -