Most epidemiologic studies to date that have examined alcohol-smoking relations have relied on one of two analytic approaches: (a) correlating current levels of alcohol use and levels of smoking or (b) comparing rates of heavy drinking or alcohol use disorders between smokers, former smokers, and nonsmokers. Such approaches, while informative, do not allow for more detailed depiction of the alcohol-smoking relationship for three reasons. First, they necessarily reduce information through dichotomization of either alcohol use disorder (AUD) history (e.g., dependent or not) or drinking history (e.g., heavy drinking or not). Second, they typically focus entirely on only one type of alcohol involvement indicator at a time, namely either an index of current drinking or an index of current or past AUD. Item response modeling has shown that indicators of involvement with alcohol generally fall along a single latent dimension that ranges from minimal drinking to heavy drinking to mild alcohol problems to severe dependence (Kahler et al., 2005
; Kahler et al., 2003
; Krueger et al., 2004
; Saha et al., 2007
). These findings indicate that it is possible to place individuals along a single continuum of lifetime alcohol involvement based on lifetime indices of drinking and alcohol-related problems. Such a continuum integrates information about drinking history and alcohol use disorder symptoms and can yield a richer and more integrated examination of how an individual’s history of alcohol involvement relates to key milestones in the lifetime smoking trajectory. For example, using an ordinal index of lifetime alcohol involvement may reveal whether the relationships between lifetime alcohol involvement and smoking outcomes are linear or take a curvilinear form in which there are regions along the alcohol involvement continuum where the odds of a given smoking outcome increase particularly rapidly with increasing alcohol involvement.
The third limitation of most prior studies of smoking and alcohol involvement is that they have collapsed lifetime smoking outcomes into categories that do not allow for a maximally informative examination of how alcohol involvement and smoking relate. Specifically, defining participants as either never, former, or current smokers, precludes a fine-grained examination of how alcohol involvement relates independently to initiation of smoking and to progression of smoking; those who never initiated smoking are typically combined in analyses with those who initiated smoking but did not progress to daily smoking. Examining initiation, progression, and persistence of smoking separately may allow for a greater understanding of how alcohol involvement relates to smoking. For example, studies have shown that prior alcohol use is associated with greater risk for initiating smoking (Jackson et al., 2002
; Wetzels et al., 2003
). However, it is not clear that increasingly high levels of alcohol involvement would be associated with increasing risk of smoking initiation. Initiation of smoking is likely to occur at an age in which alcohol use and problems have not approached their peak. Furthermore, smoking initiation is so common that rates may approach an asymptote at near 100% even at relatively moderate levels of alcohol involvement, leaving little variance in initiation to explain.
By contrast, among those who have initiated smoking, the relation between alcohol involvement and progression from initiation of smoking to daily smoking and tobacco dependence may be especially strong at higher levels of alcohol involvement. Alcohol use can potentiate the rewarding effects of smoking (Glautier et al., 1996
; Rose et al., 2002
), which could increase motivation to smoke. Thus, greater levels of alcohol involvement may be associated with a consistent linear increase in the odds of progressing to daily smoking. However, there also may be common mechanisms that contribute to both dependence on alcohol and dependence on tobacco, such as specific genetic vulnerabilities (Enoch et al., 2006
; Liu et al., 2005
; Schinka et al., 2002
). For example, the rates of current nicotine dependence among those with current alcohol dependence are markedly higher than the rates of nicotine dependence among those with alcohol abuse (Falk et al., 2006
). Likewise, among adolescents and young adults, current smokers have a significantly higher odds of an alcohol use disorder compared to never smokers who drink equivalent quantities (Grucza and Bierut, 2006
Finally, the relationship of lifetime alcohol involvement to persistence of smoking may be quite different than its relationship to progression to daily smoking and tobacco dependence. In general, current alcohol use is associated with a reduced odds of smoking cessation (Carmelli et al., 1993
; Hymowitz et al., 1997
; Osler et al., 1999
; Sobell et al., 1995
; Sorlie and Kannel, 1990
; Zimmerman et al., 1990
) with frequency of heavy alcohol use, rather than overall level of drinking, appearing to be most strongly associated with continued smoking (Dawson, 2000
; Murray et al., 1995
; Vander Ark et al., 1997
). However, although cessation rates are lower for individuals with a history of AUD compared to those without an AUD history (Dawson, 2000
), having a past history of alcohol problems does not appear to reduce the odds of successful smoking cessation on a given attempt (Hughes and Kalman, 2006
). These varying results indicate the continued need for a detailed analysis of the relationship between lifetime alcohol involvement and persistence of smoking.
In the present study, we examined the relationship between lifetime alcohol involvement and four key lifetime smoking outcomes (initiation of smoking, progression from initiation to daily smoking, progression from initiation to tobacco dependence, and persistence of smoking in middle adulthood) among 1,508 adult participants in the Transdisciplinary Tobacco Use Research Center: New England Family Study (TTURC: NEFS). To define an alcohol involvement continuum, we relied upon item response analyses based on the Rasch model (Rasch, 1960
). These Rasch analyses were used to select indicators of lifetime alcohol use and AUD symptoms that could be combined in a single additive scale that was unbiased across demographic groups. We then graphically depicted the rates of smoking initiation, progression, and persistence at each level of alcohol involvement. Finally, logistic regression models were used to examine whether the association between alcohol involvement and the log odds of smoking initiation, progression, and persistence was generally linear or showed significant curvilinear effects. We expected that alcohol involvement would relate most strongly to smoking initiation in the lower regions of the continuum and would relate to progression to daily smoking and tobacco dependence most strongly in the upper regions of the continuum. Based on equivocal evidence about the importance of a history of alcohol dependence in predicting smoking cessation outcomes, we expected a relatively weak positive linear trend between alcohol involvement and the odds of currently smoking at the time of the interview.