Main characteristics of the subjects considered in the analysis according to the GOLD severity stages, and crude relative risk ratios (RRR)* with 95% confidence intervals for the association between each risk factor and the GOLD severity stage
| No respiratory disorders (n = 12567) % | Stage 0 (n = 1751) | Stages I+ (n = 537) | |||
|---|---|---|---|---|---|
| % | RRR (95% CI) | % | RRR (95% CI) | ||
| *Calculated by multinomial regression models (reference population: subjects with neither chronic symptoms nor airflow obstruction). | |||||
| †ETS+/−: subjects exposed/not exposed to environmental tobacco smoke. | |||||
| ‡Cigars, cigarillos or pipe tobacco. | |||||
| Active/passive smoking exposure: | |||||
| Non-smokers and ETS−† | 37.9 | 21.4 | 1.00 | 24.0 | 1.00 |
| Past smokers and ETS− | 17.3 | 10.2 | 1.05 (0.87 to 1.27) | 15.6 | 1.42 (1.07 to 1.89) |
| Non-smokers and ETS+ | 7.5 | 5.4 | 1.29 (1.02 to 1.64) | 5.0 | 1.06 (0.69 to 1.62) |
| Past smokers and ETS+ | 4.4 | 3.1 | 1.23 (0.91 to 1.67) | 4.0 | 1.45 (0.91 to 2.33) |
| Smokers (<15 pack years) | 19.9 | 28.5 | 2.55 (2.20 to 2.94) | 14.4 | 1.15 (0.86 to 1.53) |
| Smokers (⩾15 pack years) | 11.5 | 30.1 | 4.65 (4.01 to 5.38) | 33.5 | 4.58 (3.62 to 5.81) |
| Smokers (other tobaccos)‡ | 1.5 | 1.3 | 1.47 (0.93 to 2.31) | 3.5 | 3.50 (2.09 to 5.86) |
| Presence of respiratory infections before the age of 5 years | 8.9 | 12.2 | 1.47 (1.26 to 1.72) | 14.1 | 1.71 (1.32 to 2.20) |
| Presence of occupational exposure to vapours, gas, dust or fumes in a lifetime | 41.6 | 54.4 | 1.67 (1.51 to 1.85) | 52.3 | 1.54 (1.29 to 1.83) |
| Low socioeconomic class | 19.5 | 29.0 | 1.68 (1.50 to 1.89) | 28.0 | 1.60 (1.30 to 1.97) |
| Females | 51.1 | 46.3 | 33.7 | ||
| Mean (SD) age (years) | 33.6 (7.2) | 33.2 (7.1) | 36.8 (6.5) | ||
| Mean (SD) FEV1 % predicted | 106.6 (13.1) | 103.9 (13.1) | 86.6 (15.1) | ||