Table 2.
Subgroup analyses regarding the risk of COPD
| Subgroups | No. studies | No. participants/Cases | OR value (95% CI) | P value | I2, % |
| Adjusted for smoking intensity* | |||||
| Yes | 10 | 27 246/3556 | 1.14 (0.86 to 1.51) | 0.38 | 67 |
| No | 8 | 22 158/5478 | 1.29 (1.13 to 1.48) | 0.0002 | 75 |
| Assessment of PD | |||||
| CAL | 8 | 24 600/3058 | 1.04 (0.96 to 1.14) | 0.33 | 75 |
| ABL | 6 | 4629/1530 | 1.98 (1.32 to 2.97) | 0.001 | 56 |
| PPD | 8 | 19 189/3519 | 1.16 (0.89 to 1.51) | 0.27 | 63 |
| Geographical location | |||||
| Asia | 9 | 18 831/3606 | 1.07 (0.99 to 1.17) | 0.08 | 65 |
| North America | 5 | 24 033/2420 | 1.37 (0.93 to 2.01) | 0.11 | 63 |
| Europe | 4 | 6540/3008 | 2.05 (1.07 to 3.95) | 0.03 | 71 |
| Assessment of COPD | |||||
| GOLD | 12 | 19 879/3774 | 1.10 (1.00 to 1.22) | 0.06 | 71 |
| Non-GOLD | 6 | 29 525/5260 | 1.35 (1.14 to 1.61) | 0.0007 | 46 |
| Study design | |||||
| Case–control | 8 | 9 911/4472 | 1.12 (1.01 to 1.24) | 0.03 | 86 |
| Cross-sectional | 9 | 38 593/4540 | 1.34 (1.08 to 1.66) | 0.007 | 45 |
| Cohort | 1 | 878/22 | 3.51 (1.15 to 10.74) | 0.03 | – |
Bold: subgroups with positive results.
*Duration and dose of smoking.
ABL, alveolar bone loss; CAL, clinical attachment level; COPD, chronic obstructive pulmonary disease; GOLD, Global Initiative for Chronic Obstructive Lung Disease; PD, periodontal disease; PPD, probing pocket depth.