Description (%) of explanatory and confounding variables by respiratory conditions (no symptoms, phlegm only, cough only, phlegm and cough) at age 29 (N=7320)
| No symptoms (%) (n=5792) | Phlegm (%) (n=214) | Cough (%) (n=675) | Phlegm+cough (%) (n=639) | |
|---|---|---|---|---|
| Explanatory variables | ||||
| Smoking status at age 10 | ||||
| Never | 88.09 | 78.97 | 84.74 | 79.50 |
| Smoked | 11.92 | 21.12 | 15.26 | 20.50 |
| Household dampness at age 10 | ||||
| No dampness | 84.34 | 83.18 | 84.15 | 76.37 |
| Slight to moderate | 13.33 | 11.68 | 12.40 | 16.91 |
| Marked | 2.33 | 5.14 | 3.41 | 6.73 |
| Numbers of adult smokers in the household at age 10 | ||||
| Zero | 36.08 | 28.50 | 29.93 | 26.60 |
| One | 36.31 | 38.32 | 35.83 | 38.50 |
| Two or more | 27.61 | 33.18 | 34.22 | 34.90 |
| Smoking status at age 29 | ||||
| Current smoker | 49.64 | 70.56 | 70.81 | 80.44 |
| Confounders | ||||
| Phlegm at age 10 | ||||
| Present | 2.05 | 5.61 | 4.00 | 4.38 |
| Cough at age 10 | ||||
| Present | 9.94 | 14.49 | 14.37 | 16.28 |
| Respiratory difficulties at birth | ||||
| Present | 2.14 | 2.34 | 2.22 | 2.19 |
| Social position of origin | ||||
| Professional and managerial | 18.42 | 20.56 | 14.67 | 13.77 |
| Skilled non-manual | 14.50 | 11.21 | 13.04 | 10.33 |
| Skilled manual | 45.51 | 42.99 | 46.96 | 48.36 |
| Non-skilled manual+no male head | 21.56 | 25.23 | 25.33 | 27.54 |
| Sex | ||||
| Male | 45.98 | 67.76 | 45.63 | 63.85 |
| Female | 54.02 | 32.24 | 54.37 | 36.15 |