Hypothetical examples of individualised predictions by baseline smoking and asthma status in a high-risk occupation: risk difference with and without quitting by age 50s
| Predictions by recalled asthma and smoking status for an at-risk occupational group*† | Predicted probability (%) | Predicted occurrence (1/n persons) | Risk category (age in 40s)‡ |
| Smoking status—no asthma or respiratory symptoms | |||
| Non-smoker | 0.6 | 166 | Minimal |
| Past smoker | 2.5 | 40 | Low |
| Current smoker at mean age 43 | |||
| Quit smoking by mean age 53 | 4.5 | 22 | Low |
| Continued smoking at 53§ | 27.0 | 3.7 | Very high |
| Smoking status—adult-onset asthma with wheeze in the last 12 months | |||
| Non-smoker | 6.4 | 16 | Moderate |
| Past smoker | 10.8 | 9.3 | High |
| Current smoker at mean age 43 | |||
| Quit smoking by mean age 53 | 16.4 | 6.1 | High |
| Continued smoking at 53¶ | 42.0 | 2.4 | Very high |
*Based on a 30 pack-year smoking history starting at age 13 and asthma onset at age 23 years.
†Based on a female worker from an at-risk occupation (eg, labourers and related workers such as cleaners, factory workers, farm and/or kitchen hands).
‡Risk categories: minimal risk if predicted occurrence of 1 in >100 similar persons; low risk if 1 in 20–100 persons; moderate risk if 1 in 10–20 persons; high risk if 1 in 5–10 persons and very high risk if 1 in 1.5–5 persons.
§Same clinical scenario has been presented in online supplemental table E7 (30 pack-years of smoking).
¶Same clinical scenario as in online supplemental table E9 except the predicted probability was for a male worker (42.5%, labelled with ‡).