Gender differences and ratios in percentages (%) of self-reported non-smokers among cotinine-verified smokers relative to demographic variables in men and women aged ≥20 years in the 2008 Korea National Health and Nutrition Examination Survey
| Study variables | Men | Women | Gender differences and ratios | |||
| Total number of subjects (%) | Self-reported non-smokers (%, 95% CI) A | Total number of subjects (%) | Self-reported non-smokers (% 95% CI) B | B − A (95% CI) | B/A (95% CI) | |
| Total | 1194 (100.0) | 12.1 (10.2–13.9) | 426 (100.0) | 58.9 (54.3–63.6) | 45.4 (40.3–50.5) | 4.85 (4.13–5.70) |
| Age groups (years) | ||||||
| 20–29 | 170 (14.2) | 12.4 (7.4–17.3) | 85 (20.0) | 52.9 (42.3–63.6) | 39.5 (29.9–49.0) | 4.51 (3.18–6.38) |
| 30–39 | 318 (26.6) | 8.8 (5.7–11.9) | 102 (23.9) | 66.7 (57.5–75.8) | 51.8 (41.5–62.1) | 6.90 (4.84–9.84) |
| 40–49 | 279 (23.4) | 12.5 (8.7–16.4) | 83 (19.5) | 61.5 (51.0–71.9) | 50.7 (40.0–61.5) | 4.90 (3.59–6.67) |
| 50–59 | 188 (15.8) | 13.8 (8.9–18.8) | 55 (12.9) | 65.5 (52.9–78.0) | 54.8 (40.6–68.9) | 5.00 (3.41–7.34) |
| 60 or over | 239 (20.0) | 14.2 (9.8–18.7) | 101 (23.7) | 50.5 (40.7–60.3) | 31.7 (17.9–45.5) | 3.14 (2.00–4.93) |
| Education | ||||||
| Elementary or less | 212 (17.8) | 11.8 (7.5–16.1) | 132 (31.0) | 49.2 (40.7–57.8) | 32.2 (20.8–43.5) | 4.05 (2.48–6.64) |
| Middle | 150 (12.6) | 10.0 (5.2–14.8) | 30 (7.0) | 53.3 (35.5–71.2) | 37.8 (18.1–57.5) | 4.83 (2.64–8.85) |
| High | 461 (38.6) | 12.2 (9.2–15.1) | 185 (43.4) | 62.2 (55.2–69.2) | 48.2 (41.0–55.4) | 5.22 (4.10–6.66) |
| College or higher | 371 (31.1) | 12.9 (9.5–16.4) | 79 (18.5) | 69.6 (59.5–79.8) | 55.2 (45.1–65.2) | 5.12 (3.93–6.66) |
| Occupation | ||||||
| Non-manual | 301 (25.2) | 13.3 (9.5–17.1) | 63 (14.8) | 60.3 (48.2–72.4) | 43.0 (31.3–54.8) | 4.19 (3.05–5.76) |
| Manual | 666 (55.8) | 11.3 (8.9–13.7) | 161 (37.8) | 60.3 (52.7–67.8) | 46.9 (38.3–55.5) | 5.39 (4.22–6.90) |
| Others | 227 (19.0) | 12.8 (8.4–17.1) | 202 (47.4) | 57.4 (50.6–64.2) | 44.6 (36.7–52.5) | 4.55 (3.27–6.33) |
| Current marital status | ||||||
| Married with cohabiting | 896 (75.0) | 12.8 (10.6–15.0) | 259 (60.8) | 68.0 (62.3–73.6) | 54.2 (47.8–60.6) | 5.38 (4.46–6.48) |
| Married without cohabiting | 19 (1.6) | 5.3 (0.0–15.3) | 4 (0.9) | 25.0 (0.0–67.4) | 15.3 (−23.5 to 54.2) | 3.22 (0.33–31.85) |
| Never-married | 222 (18.6) | 10.4 (6.4–14.4) | 68 (16.0) | 45.6 (33.8–57.4) | 36.8 (26.4–47.1) | 4.70 (3.25–6.78) |
| Divorced or widowed | 57 (4.8) | 8.8 (1.4–16.1) | 95 (22.3) | 45.3 (35.3–55.3) | 27.8 (13.0–42.7) | 2.82 (1.45–5.49) |
| Cohabiting with parents | ||||||
| Yes | 294 (24.6) | 11.6 (7.9–15.2) | 79 (18.5) | 70.9 (60.9–80.9) | 59.7 (50.2–69.1) | 6.40 (4.78–8.58) |
| No | 900 (75.4) | 12.2 (10.1–14.4) | 347 (81.5) | 56.2 (51.0–61.4) | 40.7 (34.8–46.6) | 4.37 (3.60–5.30) |
| Residential area | ||||||
| Seoul | 190 (15.9) | 12.1 (7.5–16.7) | 69 (16.2) | 42.0 (30.4–53.7) | 29.5 (17.8–41.2) | 3.48 (2.31–5.22) |
| Other cities | 710 (59.5) | 12.0 (9.6–14.4) | 269 (63.2) | 60.6 (54.8–66.4) | 48.1 (41.9–54.3) | 5.10 (4.17–6.23) |
| Rural area | 2947 (24.6) | 12.2 (8.5–16.0) | 88 (20.7) | 67.1 (57.2–76.9) | 53.5 (40.4–66.6) | 5.54 (3.76–8.16) |
| Urine cotinine (ng/ml) | ||||||
| 50–499 | 321 (26.9) | 33.6 (28.5–38.8) | 247 (58.0) | 79.0 (73.9–84.0) | 41.3 (34.0–48.6) | 2.19 (1.87–2.56) |
| 500–999 | 268 (22.5) | 7.5 (4.3–10.6) | 97 (22.8) | 32.0 (22.7–41.2) | 28.4 (18.5–38.3) | 4.60 (2.93–7.23) |
| 1000–1499 | 239 (20.0) | 3.8 (1.4–6.2) | 41 (9.6) | 41.5 (26.4–56.5) | 36.2 (20.4–52.0) | 10.45 (5.27–20.72) |
| ≥1500 | 366 (30.7) | 1.9 (0.5–3.3) | 41 (9.6) | 19.5 (7.4–31.6) | 14.4 (2.7–26.2) | 9.06 (3.42–24.02) |
| Secondhand smoking exposure | ||||||
| None | 495 (41.5) | 12.7 (9.8–15.7) | 164 (38.5) | 63.4 (56.0–70.8) | 50.1 (41.6–58.6) | 4.90 (3.82–6.28) |
| <1 h/day | 388 (32.5) | 11.3 (8.2–14.5) | 114 (26.8) | 55.3 (46.1–64.4) | 41.7 (32.3–51.1) | 4.99 (3.66–6.80) |
| ≥1 h/day | 278 (23.3) | 12.2 (8.4–16.1) | 135 (31.7) | 58.5 (50.2–66.8) | 45.6 (36.7–54.5) | 4.86 (3.57–6.62) |
| Unknown | 33 (2.8) | 9.1 (0.0–18.9) | 13 (3.1) | 38.5 (12.0–64.9) | 23.7 (−5.2–52.5) | 2.84 (0.98–8.20) |
CI, confidence interval.