| Value | Category |
|---|---|
| 1 | I have never smoked |
| 2 | I do not smoke every day |
| 3 | From 7 years of age or earlier |
| 4 | From 8 or 9 years of age |
| 5 | From 10 or 11 years of age |
| 6 | From 12 or 13 years of age |
| 7 | From 14 or 15 years of age |
| 8 | From 16 years of age or later |
| Sysmiss |