Numbers (percentages) of cases and controls by age group, parental smoking, and socioeconomic characteristics
| Cases (n = 68) | Controls (n = 135) | |
| Age group (years) | ||
| Less than 1 | 15 (22) | 30 (22) |
| 1–4 | 30 (44) | 61 (45) |
| 5–9 | 15 (22) | 29 (21) |
| 10–14 | 8 (12) | 15 (11) |
| Parental smoking | ||
| Mother smokes | 33 (50) | 25 (19) |
| Father smokes | 42 (63) | 43 (33) |
| None | 22 (32) | 82 (61) |
| Mother only | 5 (7) | 10 (7) |
| Father only | 14 (21) | 30 (22) |
| Both | 27 (40) | 13 (10) |
| Mean number (SD) of cigarettes smoked daily at homes with at least one smoker | 28.5 (13.4) | 19.6 (8.8) |
| Mother's education | ||
| Primary | 18 (27) | 13 (10) |
| Apprenticeship | 28 (42) | 54 (41) |
| Vocational | 18 (27) | 54 (41) |
| University | 3 (4) | 12 (9) |
| Father's education | ||
| Primary | 12 (18) | 14 (11) |
| Apprenticeship | 37 (55) | 70 (53) |
| Vocational | 15 (22) | 38 (29) |
| University | 3 (4) | 9 (7) |
| Material circumstances | ||
| Family owns a car | 32 (47) | 84 (64) |
| Family owns a cottage | 3 (4) | 20 (15) |
| Crowding (>1 person per room) | 36 (54) | 49 (37) |
| Number of siblings | ||
| None | 15 (22) | 33 (25) |
| 1 | 33 (49) | 71 (54) |
| 2 | 11 (16) | 21 (16) |
| 3+ | 8 (12) | 7 (5) |
| Spends weekends in countryside | ||
| <1 day a month | 22 (34) | 30 (23) |
| 1–5 days a month | 18 (28) | 33 (25) |
| >5 days a month | 25 (38) | 70 (53) |
| Heating | ||
| Central | 47 (73) | 99 (77) |
| Gas | 8 (12) | 20 (16) |
| Coal | 9 (14) | 9 (7) |
| Cooking | ||
| Gas | 38 (69) | 77 (62) |
| Electricity | 15 (27) | 44 (35) |
| Coal | 2 (4) | 3 (2) |