Physical activity and nicotine dependence among a national sample of young U.S. adults who smoke daily: Evaluation of cross-sectional and longitudinal associations to determine which behavior drives this relationship
Introduction
Chronic smoking is negatively associated with numerous chronic diseases, such as heart disease, stroke, and lung cancer and is the leading cause of preventable death in the United States (U.S.) [1]. Encouraging evidence suggests increased levels of physical activity are inversely associated with smoking, both from longitudinal and cross-sectional work [2], [3]. Other studies using cross-sectional and longitudinal designs suggest the reciprocal relationship, i.e., smoking influences physical activity behavior [4], [5], [6]. As a result, a bidirectional relationship between physical activity and smoking is suggested, which is plausible as physical activity may reduce nicotine cravings [7], favoring quit attempts [8] and success in smoking cessation [9], [10]. Conversely, smoking may displace time spent being active and often converges with other health risk behaviors (e.g., alcoholism) that are associated with physical inactivity [11].
Further investigation into a possible bidirectional relationship between physical activity and smoking is warranted. Nearly all studies examining this relationship have used discrete self-reported measures of smoking status (e.g., current smoker vs. non-smoker) [12]. However, the association between nicotine dependence and physical activity is relatively unknown and worth consideration as individuals with greater nicotine dependence have worse health outcomes (e.g., mental health disease) than those with a lower degree of nicotine dependence [13]. To our knowledge, no study has concurrently examined the cross-sectional and longitudinal associations between physical activity and nicotine dependence, and physical activity and smoking status, which was the purpose of this study. Cross-sectional assessment included examining the association between baseline physical activity and baseline nicotine dependence. Longitudinal associations examined were: 1) the association between baseline physical activity and 2-year follow-up nicotine dependence and smoking status, and 2) the association between baseline nicotine dependence and 2-year follow-up physical activity. A secondary objective was to examine if physical activity and smoking behavior track (i.e., maintained over time) over a 2-year period. To improve generalizability of our findings, data from the longitudinal National Youth Smoking Cessation Survey were used, which includes a national sample of young (16–24 yrs) daily U.S. smokers.
Section snippets
Design and participants
Data from the 2003–2005 National Youth Smoking Cessation Survey (NYSCS) were used, which is an epidemiological longitudinal study of young smokers examining factors associated with smoking cessation. The NYSCS employs a nationally representative sample of 16–24 year-olds using a single-stage, un-clustered design. Using a random digit dialing method, persons residing in households in the 50 U.S. states and the District of Columbia who smoked 20 or more lifetime cigarettes and had smoked in the
Data analysis
Continuous variables were summarized using mean ± SD and categorical variables were reported as n (weighted %). Comparisons between continuous variables were assessed using a Student's t-test. All data including the regression analyses described subsequently were analyzed using procedures from sample survey data using Stata (version 12.0, College Station, TX). Statistical significance was established as p < 0.05.
Pathway A in Fig. 1 depicts the cross-sectional relationship between baseline nicotine
Results
Weighted characteristics of the analyzed sample are shown in Table 1.
With regard to the primary analyses (weighted), see Fig. 2 for a graphical illustration of the results, with these results also reported in the narrative that follows. There was evidence of a cross-sectional bidirectional relationship between baseline nicotine dependence and baseline activity status (Pathway A). After adjusting for the demographic covariates, those meeting physical activity guidelines, compared to those not
Discussion
The purposes of this study were twofold: 1) to examine the cross-sectional and longitudinal associations between nicotine dependence and physical activity, and 2) to determine if these behaviors track over a two-year period during the early adult years. This study identified three notable findings: 1) physical activity and nicotine dependence demonstrated bidirectional, cross-sectional associations; 2) when examined longitudinally, nicotine dependence influenced physical activity, but there was
Conclusion
In conclusion, our cross-sectional findings suggest a bidirectional relationship between nicotine dependence and physical activity. However, our longitudinal findings demonstrate nicotine dependence influenced physical activity, but no evidence of the reverse pathway (i.e., physical activity influencing 2-year follow-up smoking behavior [smoking status or nicotine dependence]) was observed. Consequently, these findings suggest nicotine dependence may be driving the cross-sectional nicotine
Acknowledgements
No funding was used to prepare this manuscript.
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