Table 2.

Mean and Standard Errors of Least-Squares Mean Differences at Week 20 Between Treatment Groups as a Function of Age Group (Top Panel, Age 18–24 and Bottom Panel, Age ≥ 25)

		Age 18–24
Outcome	Interaction p-value	Immediate vs control	p	Immediate vs gradual	p	Gradual vs control	p
Total CPD	.80	−7.02 (2.98)	0.02	−6.32 (2.84)	0.03	−0.70 (2.97)	.82
Log TNE	.99	−1.71 (0.57)	<0.01	0.35 (0.51)	0.50	−2.05 (0.57)	<.01
		Age ≥ 25
Outcome	Interaction p-value	Immediate vs control	p	Immediate vs gradual	p	Gradual vs control	p
Total CPD	.80	−7.95 (0.78)	<.01	−5.20 (0.65)	<.01	−2.74 (0.76)	<.01
Log TNE	.99	−1.68 (0.15)	<.01	0.40 (0.13)	<.01	−2.08 (0.15)	<.01

Interaction test p-values represent the outcome of tests for overall significant interactions between age category and nicotine reduction group, and p-values listed for each comparison shows the significance of least-squares mean differences between age groups within each nicotine reduction group. Mean difference p-values represent the outcome of post hoc contrast test probing the interaction for significant differences by age group. Positive mean difference values indicate higher values in the younger adults compared with older adults. Regression model adjusted for age group (18–24, ≥25), nicotine group (gradual, immediate, control), value of the given outcome at baseline, FTND at baseline, race (White, African American, other), nicotine metabolite ratio at baseline and gender. Bold values indicate significant p-value. CPD = cigarettes per day, TNEs = total nicotine equivalents.