Meta-regression with subgroup analysis
| % FEV1 | % FVC | FEV1/FVC (%) | |||||||||||||
| Studies | Participants | Effect estimate | I2 | p | Studies | Participants | Effect estimate | I2 | p | Studies | Participants | Effect estimate | I2 | p | |
| Male | 5 | 667 | −13.10 (−22.57, −3.64) | 96% | 0.007 | 5 | 667 | −13.71 (−22.02, −5.39) | 95% | 0.001 | 11 | 1099 | 2.69 (0.70, 4.67) | 92% | 0.008 |
| Female | 3 | 473 | −9.00 (−19.86, 1.85) | 82% | 0.10 | 3 | 473 | −9.58 (−18.07, −1.09) | 70% | 0.03 | 7 | 737 | 2.84 (−1.89, 7.57) | 96% | 0.24 |
| Nonsmokers | 25 | 2357 | −9.67 (−13.05, −6.29) | 94% | <0.001 | 23 | 2252 | −10.84 (−14.12, −7.57) | 93% | <0.001 | 32 | 3257 | −0.21 (−3.35, 2.93) | 100% | 0.90 |
| Continent | |||||||||||||||
| Africa | 1 | 90 | NA | NA | NA | 1 | 90 | NA | NA | NA | 3 | 365 | −2.70 (−9.01, 3.62) | 99% | 0.40 |
| America | 5 | 11 966 | −4.99 (−6.72, −3.26) | 98% | <0.001 | 4 | 11 683 | −8.77 (−13.43, −4.11) | 99% | <0.001 | 6 | 12 238 | 2.48 (1.56, 3.40) | 85% | <0.001 |
| Asia | 21 | 36 202 | −7.50 (−9.01, −6.00) | 95% | <0.001 | 18 | 35 992 | −7.91 (−9.40, −6.43) | 95% | <0.001 | 26 | 36 944 | 0.02 (–1.80, 1.83) | 100% | 0.99 |
| Europe | 13 | 1432 | −8.93 (−13.25, −4.62) | 82% | <0.001 | 11 | 1372 | −11.48 (−17.38, −5.57) | 88% | <0.001 | 9 | 1149 | −1.53 (−4.21, 1.16) | 89% | 0.26 |
| Oceania | 1 | 15 | NA | NA | 0.50 | 1 | 15 | NA | NA | NA | 1 | 15 | NA | NA | NA |
| BMI (kg·m−2) | |||||||||||||||
| <25 | 9 | 1809 | −10.95 (−16.58, −5.33) | 96% | <0.001 | 5 | 927 | −12.26 (−23.01, −1.51) | 98% | 0.03 | 7 | 1152 | 1.41 (−3.31, 6.14) | 99% | 0.56 |
| 25–29.9 | 14 | 35 064 | −3.46 (−5.54, −2.38) | 94% | <0.001 | 14 | 35 515 | −5.78 (−7.03, −4.53) | 90% | <0.001 | 16 | 36 003 | −0.28 (−1.61, 1.05) | 99% | 0.68 |
| 30–39.9 | 6 | 11 856 | −6.50 (−9.14, −3.86) | 93% | <0.001 | 6 | 11 856 | −9.66 (−13.67, −5.65) | 98% | <0.001 | 5 | 11 649 | 3.25 (0.83, 5.68) | 92% | 0.009 |
| ≥40 | 3 | 352 | −10.40 (−20.45, −0.35) | 85% | 0.04 | 2 | 222 | −11.44 (−16.63, −6.24) | 0% | <0.001 | 1 | 75 | NA | NA | NA |
| % FEF25–75 | % PEF | % DLCO | |||||||||||||
| Studies | Participants | Effect estimate | I2 | p | Studies | Participants | Effect estimate | I2 | p | Studies | Participants | Effect estimate | I2 | p | |
| Male | 2 | 210 | −17.18 (−138.25, 3.89) | 94% | 0.11 | 3 | 300 | −18.55 (−20.69, −16.40) | 0% | <0.001 | 0 | NA | NA | NA | NA |
| Female | 1 | 75 | −25.30 (−42.63, −7.97) | NA | NA | 1 | 24 | −25.51 (−31.37, −19.65) | NA | NA | 0 | NA | NA | NA | NA |
| Nonsmokers | 10 | 742 | −11.04 (−16.29, −5.78) | 77% | <0.001 | 10 | 844 | −11.03 (−15.25, −6.82) | 92% | <0.001 | 12 | 851 | −7.13 (−10.62, −3.64) | 80% | <0.001 |
| Continent | |||||||||||||||
| Africa | 0 | 90 | NA | NA | NA | 1 | 90 | NA | NA | NA | 0 | 0 | NA | NA | NA |
| America | 1 | 21 | NA | NA | NA | 0 | 0 | NA | NA | NA | 0 | 0 | NA | NA | NA |
| Asia | 6 | 537 | −11.44 (−17.07, −5.81) | 77% | <0.001 | 10 | 972 | −9.34 (−12.75, −5.93) | 86% | <0.001 | 5 | 349 | −5.60 (−11.83, −0.62) | 78% | 0.08 |
| Europe | 6 | 476 | −9.88 (−18.65, −1.11) | 78% | 0.03 | 4 | 229 | −7.78 (−21.43, 5.88) | 93% | 0.26 | 7 | 502 | −8.07 (−12.34, −3.79) | 68% | <0.001 |
| Oceania | 0 | 0 | NA | NA | NA | 0 | 0 | NA | NA | NA | 0 | 0 | NA | NA | NA |
| BMI (kg·m−2) | |||||||||||||||
| <25 | 3 | 255 | −13.36 (−23.15, −3.57) | 88% | 0.007 | 4 | 345 | −13.32 (−19.69, −6.96) | 91% | <0.001 | 3 | 205 | −11.83 (−16.30, −7.36) | 0% | <0.001 |
| 25–29.9 | 1 | 35 | NA | NA | NA | 3 | 250 | −5.84 (−7.08, −4.60) | 0% | <0.001 | 6 | 507 | −5.20 (−9.72, −0.68) | 59% | 0.002 |
| 30–39.9 | 1 | 110 | NA | NA | NA | 2 | 134 | −13.12 (−37.47, 11.22) | 97% | 0.29 | 0 | 0 | NA | NA | NA |
| ≥40 | 2 | 222 | −26.04 (−34.93, −17.14) | 0% | <0.001 | 0 | 0 | NA | NA | NA | 0 | 0 | NA | NA | NA |
FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity; NA: not applicable; FEF25–75%: forced expiratory flow between 25% and 75% of total lung capacity; BMI: body mass index; PEF: peak expiratory flow; DLCO: diffusion capacity of the lung for carbon monoxide.