Table 2.

Association of 100% Hospitality Smoking Bans^a With Within-Person Change in Smoking Behaviors, Controlling for Secular Time Trends With Linear and Nonlinear Time Variables, CARDIA Study, 1985–2011^b

Smoking Behavior	No. of Persons	Models Including a Linear Time Trend		Models Including a Nonlinear Time Trend
		Adjusted RR	95% CI	Adjusted RR	95% CI
Risk of current smokingc	1,732	0.92	0.87, 0.98	0.99	0.92, 1.06
Smoking intensityd among participants who had ever smoked during follow-up	1,197	0.92	0.83, 1.01	0.99	0.89, 1.10
Quitting attemptse by current smokers	1,153	1.10	1.02, 1.19	1.04	0.94, 1.14

Abbreviations: CARDIA, Coronary Artery Risk Development in Young Adults; CI, confidence interval; RR, risk ratio.

^a A 100% smoking ban was defined as a ban mandating that all bars and restaurants be completely smoke-free, with no exceptions. Exposure was lagged by 1 year to ensure temporality. Participants were linked to state, county, and city-level smoking ban exposures based on their census tract of residence.

^b RRs were estimated using fixed-effects Poisson models with robust variance estimates. Models adjusted for the following time-varying covariates: age, education, marital status, employment status, income, living with children, current alcohol use, state cigarette tax rate, and state of residence. In the first set of models, time since baseline (in years) was included as a linear trend. In the second set of models, time and time squared were included for current smoking and smoking intensity, while restricted cubic splines (6 knots) were used for quitting attempts. Interactions between time-invariant variables (sex and race) and time since baseline were retained for current smoking and smoking intensity to allow the associations of these variables with the outcome to change over time (P for interaction < 0.05). Conditional fixed-effects models included only those participants with a change in the outcome during the follow-up period. Because of concerns about collinearity with the time trend, we also repeated analyses without controlling for age in the model and found estimates to be unchanged.

^c Versus not current smoking.

^d Average number of cigarettes smoked per day (≥10 cigarettes/day vs. <10 cigarettes/day).

^e Any attempt to quit smoking versus no quitting attempts.