Clinical characteristics of the study population according to the FEV1/FVC ratio quartile
| FEV1/FVC ratio groups (n=7960) | |||||
| 1Q: <0.76 (n=1935) | 2Q: 0.76–0.80 (n=2027) | 3Q: 0.81–0.84 (n=2088) | 4Q: ≥0.85 (n=1910) | P-trend | |
| Age (years) | 55.93±8.66 | 52.41±8.50* | 50.09±7.98*† | 48.47±7.81*†‡ | <0.001 |
| Male, n (%) | 1290 (66.67) | 1040 (51.31)* | 854 (40.90)*† | 651 (34.08)*†‡ | <0.001 |
| High income, n (%) | 230 (11.89) | 384 (18.94)* | 433 (20.74)* | 383 (20.05)* | <0.001 |
| College graduate, n (%) | 189 (9.77) | 283 (13.96)* | 360 (17.24)*† | 273 (14.29)*‡ | <0.001 |
| Current smoker, n (%) | 1167 (60.31) | 893 (43.06)* | 691 (33.09)*† | 519 (27.17)*†‡ | <0.001 |
| BMI (kg/m2) | 24.02±3.00 | 24.80±2.98* | 24.94±3.01* | 24.60±3.34*‡ | <0.001 |
| SBP (mm Hg) | 123.80±18.41 | 121.24±17.82* | 119.66±17.96*† | 118.80±17.92*† | <0.001 |
| DBP (mm Hg) | 81.72±11.09 | 80.32±11.16* | 79.65±11.40* | 78.98±11.65*† | <0.001 |
| Waist circumference (cm) | 83.31±8.04 | 83.60±8.44 | 82.54±8.73*† | 80.96±9.20*†‡ | <0.001 |
| Fasting glucose (mg/dL) | 82 (77–90) | 82 (77–91) | 82 (78–90) | 82 (77–89) | 0.390 |
| Triglyceride (mg/dL) | 139 (103–191) | 141 (104–198) | 133 (98–186)*† | 127 (94–177)*†‡ | <0.001 |
| HDL-cholesterol (mg/dL) | 44.45±9.87 | 44.33±9.91 | 44.66±9.72 | 45.50±10.15*†‡ | <0.001 |
| Creatinine (mg/dL) | 0.85±0.17 | 0.84±0.17 | 0.83±0.17* | 0.81±0.16*†‡ | <0.001 |
| Haemoglobin (g/L) | 139.70±14.46 | 137.36±15.70* | 134.48±16.34*† | 133.19±15.33*† | <0.001 |
| WCC (×109/L) | 6.70±1.83 | 6.51±1.77* | 6.43±1.73* | 6.38±1.73*† | <0.001 |
| CRP (mg/dL) | 0.15 (0.07–0.26) | 0.14 (0.06–0.23)* | 0.13 (0.06–0.24)* | 0.14 (0.06–0.23)* | <0.001 |
| FEV1 (%-predicted) | 87.89±14.59 | 97.35±12.58* | 100.25±12.18*† | 101.98±12.53*†‡ | <0.001 |
| FVC (%-predicted) | 98.24±14.05 | 98.24±12.90 | 97.22±12.24 | 93.96±12.72*†‡ | <0.001 |
Values are expressed as mean±SD for normally distributed continuous variables, median and IQR for non-normally distributed variables and percentage for categorical variables. P trend was analysed normally distributed continuous variables by ANOVA, for non-normally distributed continuous variable by Jonckheere-Terpstra tests, and for categorical variables by Cochran-Armitage test for trend. *, † and ‡ meant p<0.05 when compared with <0.76, 0.76–0.81, 0.81–0.85 groups of FEV1/FVC ratio, respectively, using Bonferroni post hoc analysis of one-way ANOVA for normally distributed continuous variables, Mann-Whitney U tests for non-normally distributed continuous variable and χ2 tests for categorical variables.
ANOVA, analysis of variance; BMI, body mass index; CRP, C reactive protein; DBP, diastolic blood pressure; FEV1, forced expiratory volume in 1 s; FVC, forced vital capacity; HDL, high density lipoprotein; SBP, systolic blood pressure; WCC, white cell count.