Table 2.

Adjusted percent change in leisure-time physical activity according to smoking status CARDIA participants, 1985-2011^a

	Black women		Black men		White women		White men
	Model coefficients (95%CI) b	P valu e	Model coefficients (95%CI) b	P value	Model coefficients (95%CI) b	P value	Model coefficients (95%CI) b	P value
Smoking status: - Never smoking (reference)	-	-	-	-	-	-	-	-
- Current smoking	−0.12 (−0.33, 0.07)	0.2	.03 (−0.13, 0.19)	0.7	−0.06 (−0.18, 0.20)	0.5	−0.02 (−0.27, 0.04)	0.8
- Past smoking	−0.11 (−0.31, 0.09)	0.3	.10 (−0.06, 0.24)	0.2	.01 (−0.18, 0.21)	0.9	−0.04 (−0.10, 0.02)	0.2
Cumulative exposure: - 10 years of smokingc	−0.10 (−0.18, −0.01)	0.01	−0.21 (−0.29, −0.12)	<0.001	−0.14 (−0.20, −0.07)	<0.001	−0.03 (−0.10, 0.03)	0.3
- 10 years since smoking cessationc	.04 (−0.8, 0.16)	0.6	.01 (−0.12, 0.13)	0.9	.04 (−0.03, 0.1)	0.3	0.06 (0, 0.13)	0.05
Overall coefficient of physical activity 10 years after quitting compared with continuing to smoke	.15 (0.02, 0.28)	0.03	.29 (0.16, 0.4)	<0.001	.25 (0.16, 0.34)	<0.001	0.19 (0.11, 0.28)	<0.001
	Adjusted % change (95%CI) b		Adjusted % change (95%CI) b		Adjusted % change (95%CI) b		Adjusted % change (95%CI) b
Overall difference in physical activity 10 years after quitting compared with continuing to smoke d	16 (2, 33)	0.03	34 (18, 52)	<0.001	28 (17, 40)	<0.001	21 (11, 32)	<0.001

^aWe used linear mixed models with correlated random subject-specific intercepts and slopes and random intercepts for study center. Fully adjusted models included fixed effects for the current smoking status (never/past/current), cumulative exposure to years of smoking and years since smoking cessation, as well as examination year, physical activity level before high-school, age at smoking start and 4-knot restricted cubic splines for education. Estimates are from 4 models according to race and sex categories (black women, black men, white women, white men).

^bThe main outcome variable, leisure-time physical activity score, was natural log-transformed to address skewness, so that exponentiated model coefficients are interpretable as the percent change in physical activity score expected for each smoking statuses or for 5-years of smoking of years since smoking cessation.

^cComputed by multiplying by 10 the adjusted model coefficients for years of smoking or years since smoking cessation.

^dAfter fitting the model for each of these four groups, we estimated the average increase in physical activity 5, 10, 15 and 20 years after cessation, relative to the expected level if smoking had continued, accounting for both immediate and cumulative covariates of smoking exposure i.e. by computing the adjusted model coefficients of past smoking – coefficient of current smoking + [number of years since smoking cessation * (coefficient of years since smoking cessation – coefficient of years of smoking)] (Appendix Figure 2). For example, for a black woman, the expected physical activity level after 10 years since smoking cessation compared to the counterfactual of continuing smoking is: exp ^{(−0.11 - (−0.12) + 10*(0.004 - (−0.01)))}-1 = exp ^(0.15) -1= 0.16; in percent=16%.