Table 1.

Odds ratios of monthly and of daily smoking at 14 year follow up, by original Non-Daily Smoking Index (NDSI) and selected demographic categories

Baseline characteristics	Smoking category at 14year follow-up
	monthly smoking			daily smoking
	N (%)	OR	95% CI	N (%)	OR	95% CI
NDSI wave 1
Never smoked a whole cigarette	675 (25.9)	0.08**	0.06−0.11	371 (14.9)	0.08**	0.06−0.10
ES-N30d	344 (41.5)	0.21**	0.15−0.29	202 (24.9)	0.18**	0.13−0.24
Low NDSI	131 (44.5)	0.22**	0.14−0.34	71 (23.3)	0.16**	0.11−0.24
Moderate NDSI	195 (60.0)	0.45**	0.29−0.58	118 (38.0)	0.36**	0.25−0.51
High NDSI	123(77.0)	0.97	0.53−1.80	78 (47.6)	0.52**	0.33−0.81
Daily smokers	347 (74.2)	1.00	ref	282 (61.4)	1.00	ref
Grade
7/8th	610 (43.7)	1.00	ref	384 (28.1)	1.00	ref
9/10th	624 (37.6)	0.54**	0.44−0.66	381(23.2)	0.53**	0.43−0.67
11/12th	544 (34.5)	0.37**	0.30−0.45	332 (22.0)	0.39**	0.31−0.49
Race
White	1264 (40.5)	1.00	ref	838(27.2)	1.00	ref
Black/African American	335 (33.4)	1.17	0.86−1.59	178 (16.7)	0.88	0.67−1.14
America Indian/Native American	65 (45.3)	1.30	0.84−2.02	37(31.9)	1.30	0.73−2.29
Asian	49 (29.7)	0.81	0.51−1.29	25 (15.9)	0.66	0.41−1.04
Other	97 (33.0)	0.93	0.68−1.28	43 (14.7)	0.53*	0.37−0.77
Sex
Male	957 (43.4)	1.00	ref	579 (26.7)	1.00	ref
Female	858 (34.2)	0.63*	0.54−0.74	543 (22.4)	0.75*	0.64−0.88
Past 30-day smokeless tobacco use
None	1602 (37.2)	1.00	ref	997 (23.9)	1.00	ref
Any	182 (57.2)	1.35	0.99−1.83	109 (33.6)	0.94	0.67−1.32

Note: N reflects the sample size prior to survey weighting and design effect adjustment; percentages reflect the proportion of each category who were monthly or who were daily smokers 14 years later, after adjusting for survey weights and design effects. ES-N30d = Ever smoked a whole cigarette, but not in the past 30-days. Data from the United States National Longitudinal Study of Adolescent to Adult Health (Add Health) survey, 1994–2008 (1).

^*p < 0.05.

^**p < 0.001.