Characteristics of subjects according to lung function categories and smoking history
| Subjects with normal spirometry | Subjects with PRISm | Subjects with airflow limitation | ||||
| Never-smoker | Smoker | Never-smoker | Smoker | Never-smoker | Smoker | |
| Subjects | 914 | 516 | 86 | 87 | 46 | 169 |
| Age (years) | 57.7±10.4 | 57.2±10.7 | 62.4±10.3 | 63.5±10.8 | 66.4±11.0 | 68.1±9.6 |
| Male | 358 (39.2) | 450 (87.2)* | 33 (38.4) | 76 (87.4)* | 24 (52.2) | 150 (88.8)* |
| BMI (kg·m−2) | 23.1±3.8 | 24.0±3.3* | 24.2±4.6 | 24.6±3.7 | 24.1±3.2 | 23.4±3.8 |
| Smoking status, current | 0 (0) | 366 (70.9)* | 0 (0) | 57 (65.5)* | 0 (0) | 83 (49.1)* |
| Smoking duration, ≥20 pack-years | 0 (0) | 307 (59.5)* | 0 (0) | 72 (82.8)* | 0 (0) | 147 (87.0)* |
| FVC (% pred) | 97.6±11.7 | 96.8±10.8 | 74.4±8.7 | 73.6±8.4 | 92.8±17.6 | 84.8±18.7* |
| FEV1 (% pred) | 99.7±11.6 | 97.2±10.6* | 73.1±7.3 | 71.8±7.4 | 76.5±16.4 | 66.3±20.1* |
| FEV1/FVC | 0.81±0.05 | 0.79±0.05* | 0.78±0.05 | 0.77±0.05 | 0.64±0.06 | 0.60±0.09* |
| TLCCT (% pred) | 86.9±12.3 | 85.1±11.7* | 74.7±12.3 | 75.5±13.4 | 90.1±13.3 | 91.3±14.0 |
| FVC/TLCCT (%) | 70.4±10.6 | 71.3±9.7 | 61.4±10.5 | 60.3±13.1 | 61.3±11.9 | 55.7±15.0* |
| Prevalence of PSE | 23 (2.5) | 187 (36.2)# | 1 (1.2) | 38 (43.7)# | 2 (4.3) | 120 (71.0)# |
| Prevalence of CLE | 17 (1.9) | 164 (31.8)# | 4 (4.7) | 40 (46.0)# | 5 (10.9) | 134 (79.3)# |
Data are presented as n, mean±sd or n (%). PRISm: preserved ratio impaired spirometry; BMI: body mass index; FVC: forced vital capacity; FEV1: forced expiratory volume in 1 s; TLCCT: total lung capacity measured by computed tomography; PSE: paraseptal emphysema; CLE: centrilobular emphysema. *: statistically significant (p<0.05) compared to never-smokers within the same lung function category; #: statistically significant (adjusted p<0.05, adjusted by Bonferroni method) compared to never-smokers within the same lung function category. The adjusted p-values comparing PRISm and other lung function categories in smokers were as follows. PSE: versus normal spirometry p=1.00, versus airflow limitation p<0.01; CLE: versus normal spirometry p=0.21, versus airflow limitation p<0.01.