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.

The association between nicotine dependence and physical activity (PA) is relatively unknown. No study has concurrently examined the cross-sectional and longitudinal associations between PA and nicotine dependence, which was the primary purpose of this study. A secondary purpose was to examine how well nicotine dependence and PA behavior track over a two-year period. Data from the 2003-2005 National Youth Smoking Cessation Survey (NYSCS) were used, with young adults (18-24 yrs; n=1168) being followed over a two-year period. Physical activity was assessed using a questionnaire and nicotine dependence was assessed using the modified Fagerstrom Test for Nicotine Dependence scale. This study identified three notable findings: 1) baseline PA and nicotine dependence demonstrated a bidirectional, cross-sectional association (e.g., β=-0.23; 95% CI: -0.44 to -0.02; p=0.02); 2) when examined longitudinally, nicotine dependence influenced PA (OR=0.90; 95% CI: 0.82-0.99; p=0.04), but there was no evidence of the reverse pathway (i.e., PA influencing 2-year follow-up smoking status [OR=0.95; 95% CI: 0.66-1.39; p=0.82) or nicotine dependence (β=0.05; 95% CI: -0.14 to 0.24, p=0.61]); and 3) both PA (OR=3.52, 95% CI: 2.68-4.69; p<0.001) and nicotine dependence (β=0.52; 95% CI: 0.46-0.58, p<0.001) tracked relatively well over a two-year period during early adulthood. These findings suggest that both behaviors (physical activity and nicotine dependence) track over time, but nicotine dependence appears to be driving the cross-sectional relationship between nicotine dependence and physical activity, as opposed to the reverse pathway.