Table 1.
Demographic and smoking characteristics by subgroup.
| Baseline characteristicd | Former experimentersa N = 304 |
Recent experimentersb N = 594 |
Current Smokersc N = 152 |
|---|---|---|---|
| Female sex, n (%) | 170 (55.9) | 344 (57.9) | 71 (46.7) |
| Mean age, years, mean (SD) | 15.7 (0.62) | 15.6 (0.62) | 15.8 (0.63) |
| Race/ethnicity | |||
| Non-Hispanic White, n (%) | 151 (49.7) | 327 (55.1) | 107 (70.4) |
| Non-Hispanic Black, n (%) | 66 (21.7) | 96 (16.2) | 10 (6.6) |
| Hispanic, n (%) | 55 (18.1) | 117 (19.7) | 24 (15.8) |
| Asian/Pacific Islander, n (%) | 13 (4.3) | 17 (2.9) | 4 (2.6) |
| American Indian/Alaska Native, n (%) | 0(0) | 2 (0.3) | 0 (0) |
| Smoked in the past 24 h, n (%) | 7 (2.3) | 70 (11.8) | 93 (61.6) |
| Smoked in the past week, n (%) | 26 (8.6) | 230 (39.2) | 124 (83.2) |
| Other tobacco use in past 30 days, n (%) | 38 (12.5) | 189 (32.1) | 71 (46.7) |
| Ever smoked daily in lifetime, n (%) | 22 (7.3) | 90 (15.2) | 119 (79.3) |
| Smoked daily in the past month, n (%) | 0 (0) | 4 (0.7) | 45 (29.6) |
| Age of initiation in years, mean (SD) | 12.2 (2.13) | 12.7 (2.03) | 11.7 (1.91) |
| Mother’s smoking status, n (%) | |||
| Current smoker | 65 (22.9) | 139 (24.7) | 61 (41.5) |
| Ex-smoker | 69 (23.9) | 133 (23.6) | 35 (23.8) |
| Never-smoker | 151 (53.2) | 291 (51.7) | 51 (34.7) |
| Father’s smoking status, n (%) | |||
| Current smoker | 87 (36.3) | 157 (32.5) | 58 (43.9) |
| Ex-smoker | 66 (27.5) | 136 (28.2) | 27 (20.5) |
| Never-smoker | 87 (36.3) | 190 (39.3) | 47 (35.6) |
| Smoking regularitye, mean (SD) | 0.5 (1.48) | 3.2 (5.35) | 18.2 (11.06) |
| At 6-month assessment | 1.1 (3.46) | 4.1 (6.83) | 18.7 (11.90) |
| At 15-month assessment | 2.1 (5.89) | 5.7 (9.47) | 20.1 (12.32) |
| At 24-month assessment | 3.1 (7.78) | 7.2 (10.54) | 19.5 (12.21) |
| At 48-month assessment | 7.0 (11.13) | 10.5 (12.37) | 19.2 (12.78) |
| Smoking quantityf, mean (SD) | 0.2 (1.66) | 2.0 (5.58) | 19.4 (23.58) |
| At 6-month assessment | 0.6 (3.35) | 2.5 (7.74) | 24.1 (27.12) |
| At 15-month assessment | 1.9 (9.34) | 5.3 (15.12) | 32.6 (37.98) |
| At 24-month assessment | 2.9 (11.05) | 7.6 (12.30) | 25.8 (30.92) |
| At 48-month assessment | 9.3 (22.8) | 15.9 (31.5) | 38.3 (44.53) |
| NDSS score, mean (SD) of 10 items on a scale of 1–4 | 1.0 (0.27) | 1.2 (0.52) | 2.2 (0.86) |
| At 6-month assessment | 1.0 (0.35) | 1.3 (0.63) | 2.2 (0.87) |
| At 15-month assessment | 1.1 (0.50) | 1.4 (0.72) | 2.3 (0.89) |
| At 24-month assessment | 1.1 (0.58) | 1.4 (0.75) | 2.3 (0.89) |
| At 48-month assessment | 1.9 (0.84) | 2.1 (0.86) | 2.6 (0.86) |
a
At screening, youths who had smoked <100 cigarettes/lifetime but had not smoked in the past 90 days.
b
At screening, youths who had smoked <100 cigarettes/lifetime and had smoked in the past 90 days.
c
At the screening phase of the study, youths who had smoked >100 cigarettes/lifetime, had smoked in the past 30 days, but smoke ≤5 cigarettes/day.
d
Percentages based on valid responses.
e
Smoking regularity is defined as the number of days smoked in the past 30 days.
f
Smoking quantity is defined as the number of cigarettes smoked in the past 7 days.