标题：Smoking Initiation Associated With Specific Periods in the Life Course From Birth to Young Adulthood: Data From the National Longitudinal Survey of Youth 1997
摘要：Objectives. Guided by the life-course perspective, we examined whether there were subgroups with different likelihood curves of smoking onset associated with specific developmental periods. Methods. Using 12 waves of panel data from 4088 participants in the National Longitudinal Survey of Youth 1997, we detected subgroups with distinctive risk patterns by employing developmental trajectory modeling analysis. Results. From birth to age 29 years, 72% of female and 74% of US males initiated smoking. We detected 4 exclusive groups with distinctive risk patterns for both genders: the Pre-Teen Risk Group initiated smoking by age 12 years, the Teenage Risk Group initiated smoking by age 18 years, the Young Adult Risk Group initiated smoking by age 25 years, and the Low Risk Group experienced little or no risk over time. Groups differed on several etiological and outcome variables. Conclusions. The process of smoking initiation from birth to young adulthood is nonhomogeneous, with distinct subgroups whose risk of smoking onset is linked to specific stages in the life course. Studies suggest that there have been recent increases in adolescent smoking in the United States. 1,2 More effective prevention requires further understanding of tobacco use etiology. Numerous researchers have documented the timing and risk of early onset of tobacco use. 3–8 Although children as young as 4 to 5 years have reported smoking, 3,4 the hazard of smoking onset (defined as the probability for a never-smoker to initiate smoking during a 1-year period) is relatively low (0%–3%) before age 10 years. 3–6 The risk then increases rapidly to peak at around age 14 to 16 years, with initiation rates ranging from 5% to 15%, depending on study population and time of measurement, before it declines. 3–6 The risk of smoking initiation in later adolescence and early adulthood remains at less than 10%. 9–13 Despite this general age pattern of the risk of smoking onset, it remains unclear whether there are actual subgroups with unique risk curves associated with different developmental periods. Most studies of smoking risk trajectories are based, either implicitly or explicitly, on the assumption that 1 probability curve quantifies the risk of smoking onset for all individuals across ages and developmental periods, which may not be the case. An additional limitation of the current literature is that much of the previous research has relied on cross-sectional or brief longitudinal samples of adolescents rather following adolescents through young adulthood. According to the life-course perspective, 14–16 the interplay of intrapersonal factors and environmental factors determines who is at risk for smoking initiation at what time periods (i.e., ages). Such influential factors may include age- and development-related differences in individual vulnerability to tobacco use 17 and external influences such as peer pressure, parental monitoring, and social support. 11,18–20 Therefore, the process of smoking onset may not be homogeneous but diverse, involving subgroups of individuals with unique time patterns corresponding to different developmental periods in the life span. In general, very young children and adolescents are less likely than older adolescents to be self-motivated to smoke. 21 Rather, children are likely to be influenced by external factors, such as parents and peers. 22–24 For example, some young adolescents may be left home alone around friends who smoke; they may mimic others and simply pick up a cigarette. Those who pass through preadolescence without smoking may face new risks in high school. Most youths have more freedom from their parents in high school than they did previously. The increased unsupervised time allows adolescents more opportunities to start smoking when they feel the need, such as being with other smokers or feeling stressed or depressed. 25,26 Research among young adults (primarily college students) indicates that lack of self-efficacy, being more rebellious, and previous use of other substances are among the most influential factors for smoking onset in this period. 10,11,18 Further support for the existence of subgroups for smoking initiation is the research finding of subgroups with different trajectories in frequency and amount of tobacco use. 27–38 Labels vary, but typical subgroups reported by these studies include nonsmokers, occasional smokers, early and late stable smokers, escalators, and quitters. Although not linked to specific developmental periods, each subgroup has its own risk curve across the age span from adolescence to young adulthood. Additionally, researchers have found significant differences in a variety of factors among trajectory subgroups, including gender, race/ethnicity, mental health, and parental monitoring. 27–38 A landmark longitudinal study found that early stable smokers had more smoking friends than experimenters, abstainers, late stable smokers, and quitters; abstainers were more likely than early and late stable smokers to have enrolled in college; and late stable smokers were least likely to be married. 31 We are not aware of other research examining subgroups with time patterns of smoking onset risk that are directly linked to specific periods in the life span, which has direct implications for smoking prevention. Guided by the life-course perspective, we used 12 rounds of panel data from a nationally representative sample. Our goals were to detect subgroups with distinctive time patterns regarding likelihood of smoking initiation and then to determine whether the detected subgroups varied systematically by established risk factors in adolescence and outcome measures in young adulthood.
