Overall sample | 6839 | 39.7 | – | – | 3448 | 25.2 | – | – |
Demographic characteristics
| | | | | | | | |
Age (years) | | | | | | | | |
18–25 (referent) | 457 | 27.6 | <0.001 | – | 352 | 12.1 | <0.001 | – |
26–35 | 980 | 35.6 | 1.45 (1.22 to 1.72) | – | 588 | 19.4 | 1.75 (1.34 to 2.28) | – |
36–45 | 1718 | 44.5 | 2.10 (1.78 to 2.48) | – | 857 | 33.2 | 3.60 (2.79 to 4.64) | – |
46–55 | 1642 | 45.6 | 2.20 (1.85 to 2.62) | – | 731 | 34.5 | 3.81 (2.90 to 5.01) | – |
56+ | 2042 | 42.2 | 1.91 (1.60 to 2.30) | – | 920 | 31.7 | 3.37 (2.53 to 4.49) | – |
Sex | | | | | | | | |
Female (referent) | 4354 | 38.2 | <0.011 | – | 2191 | 23.1 | <0.006 | – |
Male | 2464 | 41.2 | 1.14 (1.03 to 1.25) | – | 1247 | 27.1 | 1.24 (1.07 to 1.43) | – |
Education | | | | | | | | |
Non-HS graduate (referent) | 701 | 32.4 | <0.001 | – | 422 | 18.7 | <0.001 | – |
High school (HS) graduate | 2324 | 37.9 | 1.27 (1.07 to 1.52) | – | 1179 | 23.7 | 1.35 (1.04 to 1.75) | – |
Some college | 2230 | 39.9 | 1.39 (1.17 to 1.65) | – | 1112 | 25.3 | 1.48 (1.14 to 1.91) | – |
Associate degree | 602 | 48.7 | 1.99 (1.59 to 2.47) | – | 283 | 31.9 | 2.04 (1.47 to 2.84) | – |
Bachelor degree | 640 | 44.7 | 1.69 (1.35 to 2.10) | – | 300 | 34.3 | 2.28 (1.65 to 3.14) | – |
Postgraduate degree | 310 | 43.5 | 1.61 (1.20 to 2.16) | – | 134 | 25.7 | 1.51 (0.94 to 2.42) | – |
Annual household income | | | | | | | | |
Under $15000 (referent) | 1403 | 34.5 | <0.001 | – | 807 | 21.1 | <0.001 | – |
$15000–$24999 | 1026 | 34.8 | 1.02 (0.85 to 1.21) | – | 540 | 21.7 | 1.04 (0.80 to 1.34) | – |
$25000–$39999 | 1452 | 36.4 | 1.09 (0.93 to 1.27) | – | 728 | 23.4 | 1.14 (0.90 to 1.44) | – |
$40000–$59999 | 1458 | 42.8 | 1.42 (1.22 to 1.66) | – | 692 | 29.2 | 1.54 (1.23 to 1.94) | – |
$60000+ | 1500 | 47.1 | 1.70 (1.46 to 1.97) | – | 681 | 29.9 | 1.60 (1.27 to 2.00) | – |
Smoking status and history
| | | | | | | | |
Cigarettes per day | | | | | | | | |
10 or less (referent) | 1624 | 29.7 | <0.001 | – | 947 | 13.6 | <0.001 | – |
11–14 | 373 | 36.4 | 1.35 (1.07 to 1.71) | – | 198 | 22.2 | 1.81 (1.26 to 2.60) | – |
15–20 | 2807 | 41.8 | 1.71 (1.50 to 1.94) | – | 1356 | 27.7 | 2.42 (1.97 to 2.98) | – |
21–30 | 1280 | 46.8 | 2.08 (1.79 to 2.42) | – | 614 | 35.8 | 3.53 (2.79 to 4.48) | – |
31+ | 717 | 46.4 | 2.06 (1.71 to 2.47) | – | 317 | 34.5 | 3.34 (2.50 to 4.46) | – |
Daily smoking | | | | | | | | |
No (referent) | 445 | 23.8 | <0.001 | <0.001 | 275 | 10.0 | <0.001 | <0.008 |
Yes | 6394 | 41.0 | 2.22 (1.80 to 2.73) | 1.50 (1.19 to 1.90) | 3173 | 26.7 | 3.27 (2.27 to 4.70) | 1.73 (1.16 to 2.57) |
Years of smoking | | | | | | | | |
10 or less (referent) | 641 | 27.0 | <0.001 | <0.001 | 489 | 12.7 | <0.001 | <0.001 |
11–20 | 1152 | 36.9 | 1.58 (1.35 to 1.85) | 1.59 (1.33 to 1.91) | 641 | 20.9 | 1.82 (1.43 to 2.32) | 1.70 (1.29 to 2.23) |
21–30 | 1789 | 45.9 | 2.29 (1.97 to 2.67) | 2.52 (1.99 to 3.19) | 872 | 34.6 | 3.65 (2.89 to 4.60) | 3.57 (2.48 to 5.16) |
31–40 | 1549 | 47.1 | 2.41 (2.04 to 2.86) | 2.87 (2.08 to 3.97) | 678 | 35.7 | 3.83 (2.95 to 4.97) | 3.91 (2.36 to 6.48) |
41+ | 1647 | 42.6 | 2.00 (1.67 to 2.40) | 3.18 (2.04 to 4.95) | 743 | 33.4 | 3.45 (2.60 to 4.57) | 4.80 (2.38 to 9.68) |
Number of quit attempts | | | | | | | | |
0–2 (referent) | 2353 | 32.6 | <0.001 | <0.001 | 958 | 25.4 | <0.364 | <0.435 |
3–5 | 2196 | 39.5 | 1.35 (1.20 to 1.53) | 1.38 (1.21 to 1.56) | 1158 | 25.1 | 0.99 (0.82 to 1.19) | 0.96 (0.79 to 1.17) |
6–10 | 1255 | 44.5 | 1.66 (1.44 to 1.91) | 1.69 (1.46 to 1.96) | 717 | 23.2 | 0.89 (0.72 to 1.11) | 0.84 (0.67 to 1.05) |
11+ | 1035 | 49.5 | 2.03 (1.75 to 2.36) | 2.00 (1.71 to 2.34) | 615 | 27.3 | 1.11 (0.89 to 1.38) | 0.99 (0.79 to 1.26) |
Smoking dependence
| | | | | | | | |
FTND | | | | | | | | |
1 or less (referent) | 866 | 23.5 | <0.001 | <0.001 | 513 | 10.5 | <0.001 | <0.001 |
1<FTND⩽3 | 1413 | 33.9 | 1.67 (1.39 to 2.01) | 1.83 (1.48 to 2.25) | 739 | 19.2 | 2.03 (1.49 to 2.76) | 1.92 (1.36 to 2.73) |
3<FTND⩽5 | 2103 | 41.9 | 2.35 (1.98 to 2.79) | 2.74 (2.12 to 3.55) | 1031 | 27.5 | 3.24 (2.43 to 4.31) | 2.97 (1.95 to 4.52) |
5<FTND⩽7 | 1483 | 47.5 | 2.94 (2.46 to 3.53) | 3.57 (2.67 to 4.77) | 694 | 33.3 | 4.25 (3.15 to 5.73) | 3.74 (2.34 to 5.98) |
7<FTND | 686 | 54.0 | 3.82 (3.09 to 4.72) | 5.04 (3.56 to 7.12) | 330 | 43.7 | 6.62 (4.76 to 9.20) | 5.91 (3.44 to 10.16) |
Time to first cigarette | | | | | | | | |
After 60 minutes (referent) | 904 | 24.0 | <0.001 | – | 541 | 10.3 | <0.001 | – |
31–60 minutes | 964 | 35.6 | 1.74 (1.44 to 2.12) | – | 484 | 19.9 | 2.16 (1.56 to 2.99) | – |
6–30 minutes | 3013 | 41.3 | 2.22 (1.89 to 2.61) | – | 1497 | 27.4 | 3.28 (2.49 to 4.32) | – |
Within 5 minutes | 1908 | 48.0 | 2.92 (2.46 to 3.46) | – | 899 | 35.1 | 4.71 (3.54 to 6.26) | – |
NDSS-T | | | | | | | | |
−3 or less (referent) | 573 | 20.9 | <0.001 | <0.001 | 326 | 11.7 | <0.001 | <0.001 |
−3<NDSS⩽−1.5 | 1211 | 31.5 | 1.75 (1.38 to 2.21) | 1.65 (1.29 to 2.11) | 618 | 14.2 | 1.25 (0.85 to 1.86) | 0.98 (0.65 to 1.48) |
−1.5<NDSS⩽0 | 1331 | 38.2 | 2.35 (1.86 to 2.96) | 2.15 (1.68 to 2.75) | 666 | 24.3 | 2.42 (1.68 to 3.50) | 1.82 (1.23 to 2.68) |
0<NDSS⩽1.5 | 1213 | 43.8 | 2.96 (2.35 to 3.73) | 2.75 (2.14 to 3.53) | 592 | 28.2 | 2.97 (2.06 to 4.29) | 2.26 (1.52 to 3.36) |
1.5<NDSS | 1602 | 52.2 | 4.15 (3.31 to 5.19) | 3.73 (2.89 to 4.82) | 776 | 38.6 | 4.75 (3.34 to 6.77) | 3.28 (2.20 to 4.90) |
Craving (at last quit) | | | | | | | | |
Not present/mild (1,2; referent) | 1919 | 31.0 | <0.001 | <0.001 | 1006 | 18.7 | <0.001 | <0.011 |
Moderate (3) | 2568 | 40.8 | 1.53 (1.35 to 1.73) | 1.36 (1.20 to 1.55) | 1327 | 25.8 | 1.51 (1.25 to 1.83) | 1.25 (1.02 to 1.53) |
Severe (4) | 2214 | 46.9 | 1.96 (1.73 to 2.23) | 1.63 (1.42 to 1.87) | 1078 | 30.3 | 1.89 (1.55 to 2.29) | 1.38 (1.12 to 1.71) |
Withdrawal (at last quit) | | | | | | | | |
1.3 or less (referent) | 1141 | 21.2 | <0.001 | <0.001 | 584 | 10.6 | <0.001 | <0.001 |
1.3<WD⩽2 | 2058 | 34.6 | 1.97 (1.66 to 2.34) | 1.93 (1.62 to 2.31) | 1048 | 20.3 | 2.15 (1.60 to 2.89) | 2.14 (1.57 to 2.90) |
2<WD⩽3 | 2195 | 46.4 | 3.22 (2.72 to 3.81) | 3.06 (2.57 to 3.65) | 1135 | 30.1 | 3.63 (2.73 to 4.84) | 3.38 (2.50 to 4.57) |
3<WD | 1310 | 53.4 | 4.26 (3.55 to 5.12) | 3.96 (3.25 to 4.81) | 644 | 37.8 | 5.13 (3.79 to 6.95) | 4.42 (3.20 to 6.11) |
Difficulty in quitting | | | | | | | | |
2 or less (referent) | 564 | 20.4 | <0.001 | <0.001 | 266 | 10.4 | <0.001 | <0.001 |
2<Diff⩽5 | 1002 | 24.9 | 1.29 (1.00 to 1.67) | 1.24 (0.95 to 1.61) | 530 | 9.8 | 0.94 (0.59 to 1.50) | 0.88 (0.55 to 1.43) |
5<Diff⩽7 | 1055 | 27.2 | 1.46 (1.14 to 1.86) | 1.40 (1.09 to 1.80) | 586 | 13.1 | 1.30 (0.84 to 2.01) | 1.24 (0.79 to 1.95) |
7<Diff⩽9 | 2128 | 43.0 | 2.93 (2.34 to 3.68) | 2.70 (2.13 to 3.41) | 1043 | 26.9 | 3.18 (2.13 to 4.75) | 2.71 (1.79 to 4.11) |
9<Diff⩽10 | 2090 | 56.8 | 5.12 (4.07 to 6.44) | 4.52 (3.56 to 5.74) | 1023 | 45.0 | 7.06 (4.73 to 10.53) | 5.62 (3.70 to 8.52) |
Medical and psychiatric history
| | | | | | | | |
Smoking related disease | | | | | | | | |
Not reported (referent) | 2259 | 38.5 | <0.001 | <0.005 | 1170 | 23.0 | <0.001 | <0.225 |
Reported | 3028 | 45.2 | 1.32 (1.18 to 1.47) | 1.19 (1.05 to 1.34) | 1475 | 29.7 | 1.41 (1.20 to 1.67) | 1.12 (0.93 to 1.35) |
Psychiatric condition | | | | | | | | |
Not reported (referent) | 1222 | 38.1 | <0.006 | <0.001 | 595 | 25.1 | <0.511 | <0.121 |
Reported | 4065 | 42.8 | 1.22 (1.06 to 1.40) | 1.30 (1.13 to 1.51) | 2050 | 26.5 | 1.07 (0.87 to 1.33) | 1.20 (0.95 to 1.51) |