Description of the seven different methods to model smoking histories (two Italian areas, 1990–1992)
| Model | Smoking habit | Pack years | Parameters* | AIC |
|---|---|---|---|---|
| *All models also include age (five parameters) and study area (five parameters). | ||||
| AIC, Akaike’s information criterion; pyrs, pack years. | ||||
| 1 | – | – | 0 | 3001.32 |
| 2 | Ever, never | – | 1 | 2780.61 |
| 3 | Current, ex, never | – | 2 | 2685.70 |
| 4 | Current 20+ pyrs, 10–19 pyrs, 1–9 pyrs, ex, never | – | 4 | 2628.51 |
| 5 | Current, ex, never | Continuous | 3 | 2615.99 |
| 6 | Current, ex since 2–5 years, 6–10 years, 11–15 years, 16+ years, never | Continuous | 6 | 2602.88 |
| 7 | Current, ex since 2–5 years, 6–10 years, 11–15 years, 16+ years, never | Cubic b-splines. Knots at 10, 20, 30, 40 pyrs | 13 | 2587.08 |