摘要：Objectives. We investigated whether socioeconomic circumstances at different life stages influence persistent smoking. Methods. We followed a British birth cohort (all births between March 3 and 9, 1958) for 41 years to examine the influence of childhood and adulthood socioeconomic position on persistent smoking in adulthood (n = 6541). Results. Persistent smoking (19% of participants, n = 1216) showed strong social gradients with both childhood and adulthood socioeconomic measures. Among men, the association with childhood socioeconomic circumstances was no longer significant after we adjusted for adulthood socioeconomic circumstances; however, among women, the adjusted odds of persistent smoking increased by 8% for each unit increase across a 16-point childhood score. Conclusions. Childhood socioeconomic circumstances predicted persistent smoking among women in our cohort, a finding that highlights the importance of influences on the development of persistent smoking across the life course. Prolonged tobacco use is recognized as the most important and the most preventable cause of premature mortality in industrial countries. It is estimated that among those who smoke regularly throughout their adult lives, about half will die from smoking-related diseases. 1 In industrial countries, most smokers begin smoking in their teenage years, 2 and the majority of regular smokers continue smoking into middle age. 3 Throughout adulthood, socioeconomic disadvantage is associated with persistent smoking, whereas higher socioeconomic status is associated with higher rates of smoking cessation. 3 These socioeconomic differentials in smoking persistence contribute to socioeconomic gradients in health, making the determinants of smoking differentials key objects of inquiry for public health research and policy. 4 Longitudinal research has begun to open 2 important lines of inquiry. First, a small number of studies have examined the contribution of socioeconomic circumstances in childhood and adulthood to smoking risk in adulthood. 5– 11 These studies indicate possible gender differences in influences on lifetime smoking. Adult socioeconomic status is reported to be more important than childhood social class 5– 7 and education 12 in influencing smoking among men. Among women, childhood socioeconomic circumstances 8, 11 and education 8– 11 have an effect on adult smoking beyond that of adult socioeconomic circumstances. Second, the pathways that underlie the relationship between childhood disadvantage and smoking status have been examined in another cluster of studies. Important mediators identified in these studies are factors related to family background, including parental smoking 13, 14 and the young person’s educational track, 15 which in turn are related to parental education and social class. 16 Other factors affecting the pathway to adult socioeconomic position, including labor market experiences 17, 18 and, among women, early and single parenthood, 19, 20 also are associated with smoking status in early adulthood. These 2 fields of research mainly focus on current smoking and rely on restricted markers of socioeconomic position. Therefore, they do not examine duration of exposure to poor socioeconomic conditions, which is suggested to be a potentially important influence on adult smoking behavior. 20, 21 We extended previous research by using longitudinal data from the 1958 British birth cohort described in further detail later in this article. We examined the influence of socioeconomic circumstances, which were measured by occupational class at different life stages, on prolonged tobacco use from 23 to 41 years of age. With information on socioeconomic circumstances at several time points, we investigated whether both childhood and adulthood socioeconomic circumstances influence smoking persistence (i.e., there is a cumulative effect) or whether socioeconomic influences are confined to a particular life stage (childhood or adulthood). Additionally, we sought to identify potential mediating factors through which socioeconomic circumstances at different life stages might affect smoking persistence. We looked specifically at the contribution of parental smoking and other dimensions of socioeconomic position (notably parental education and the individual’s own education and reproductive and labor market experiences) to the risk of persistent smoking among men and among women. Because smoking may be a predictor of an individual’s social trajectory 17 rather than the reverse, we considered as a secondary issue whether the effects of adult socioeconomic position are the result of the influence of early smoking behavior on adult social trajectories. Sample The 1958 British birth cohort included all individuals born in England, Wales, and Scotland between March 3 and 9, 1958. Data were collected as part of the National Child Development Study; details are published elsewhere. 22 In brief, the survivors of some 17 000 live births were re-interviewed at the ages of 7, 11, 16, 23, 33, and 41 years (11 373 forty-one-year-old participants reported information about smoking). In general, biases associated with sample attrition have tended to be small, although they are in the direction of underrepresentation of more deprived social groups over time. For example, in the sample used for multivariate analysis (n = 3180), 20.8% of the participants were born into social classes IV and V or had no male head of household, compared with 24.3% in the live-birth sample (n = 16 595). With respect to father’s education, 59.6% of cohort participants’ fathers had left school at less than 15 years of age in the live-birth sample, compared with 59% in the multivariate sample. At the 16-year time point, 33.1% of cohort participants smoked cigarettes, compared with 28% in the multivariate sample. Measures Smoking behavior was reported at age 16, 23, 33, and 41 years. Smokers were defined as those who reported smoking 1 or more cigarettes per week at 16 years of age and those who reported smoking 1 or more cigarettes per day at 23, 33, and 41 years of age. Persistent smokers were defined as those who smoked at 23, 33, and 41 years of age. This definition allowed inclusion of individuals who began smoking later in adolescence (after 16 years of age) but had stable smoking habits at 41 years of age. Social class was classified in accordance with the Registrar General’s Occupational Scale, 23 which ranges from class I (professional) to class V (unskilled manual) on an ordinal scale. Social class of the cohort participant’s father was recorded at birth and at 7, 11, and 16 years of age. At 23, 33, and 41 years of age, the participant’s current or most recent class was recorded for both men and women. Social class was used as a continuous variable at each age: 1 represented classes I and II, 2 represented class III nonmanual, 3 represented class III manual, and 4 represented classes IV and V. When social class at 7 years of age was missing, the value at 11 years of age was used; similarly, when social class at 11 years of age was missing, the value at 16 years of age was used, provided that social class at 7 years of age was not also missing. Cohort participants with no male head of household were included with classes IV and V. Rather than use separate measures of social class at each age, cumulative socioeconomic position scores were calculated for childhood and adulthood. For childhood, scores at birth and at 7, 11, and 16 years of age were summed to produce a cumulative score that ranged from 4 (most favorable circumstances) to 16 (least favorable). For adulthood, scores at 23, 33, and 41 years of age were summed to produce a similar scale that ranged from 3 to 12. Because occupation-based measures of socioeconomic position may misclassify women, 11, 24 an alternative measure also was used that was based on housing tenure (owner, renter, or other at 7 to 41 years of age). Potential mediating factors include those related to the social environment of the home; father’s educational level is another dimension of socioeconomic position and was used in our study as a mediating factor, partly because, unlike occupational class, educational level is not measured at several time points. Also, for the parents’ generation, parental education (leaving school before 15 years of age or leaving school at 15 years of age or later) was relatively homogenous. Parental smoking was reported when the participant was 16 years of age. The participant’s education was measured as the highest educational qualification achieved by 23 years of age and was coded as higher education, A level (or equivalent), O level (or equivalent), less than O level (or equivalent), or none. These are broadly comparable to US classifications of above high school diploma; high school diploma/grade 12; grade 10; less than grade 10; or no qualifications. Reproductive pathways were indexed according to the participants’ age at the birth of their first child (< 23 years of age or ≥ 23 years of age) and, among women, according to single-parenthood experience for 1 or more months by 33 years of age. (Single parenthood was not investigated for men, because few were single parents: n = 7 by 23 years of age; n = 82 by 33 years of age.) Unemployment was included to tap the potential influence of labor market experiences on men. Classification of unemployment among women was difficult because of the tendency for unemployed women to categorize themselves as homemakers rather than as unemployed. Unemployment was defined as being out of the labor market for 12 or more months between 1981 and 1991 as a result of being unemployed, being in a government training program, being a full-time student, being a homemaker or childcare provider, being sick and unable to work, or other.
