Table 1. The baseline characteristics of all eligible studies in this meta-analysis.
| Author | Year | Study design | Control source | Country | Matched | COPD diagnosis | MetS diagnosis | Sample size | Mean age (years) | Male gender | Mean BMI (kg/m2) | Mean FEV1 (%) | Mean FEV1 to FVC ratio | MetS | NOS score | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Cases | Controls | Cases | Controls | Cases | Controls | Cases | Controls | Cases | Controls | Cases | Controls | Cases | Controls | |||||||||
| Gupta (ATP III) [10] | 2017 | Cross-sectional | Hospital | India | Yes | GOLD | ATP III | 90 | 45 | 0.689 | 0.578 | 23.29 | 22.59 | NA | NA | NA | NA | 0.156 | 0.000 | 6 | 53.1 | 54.5 |
| Gupta (IDF) [10] | 2017 | Cross-sectional | Hospital | India | Yes | GOLD | IDF | 90 | 45 | 0.689 | 0.578 | 23.29 | 22.59 | NA | NA | NA | NA | 0.333 | 0.000 | 6 | 53.1 | 54.5 |
| Waschki [18] | 2016 | Nested | Hospital | Germany | Yes | GOLD | IDF | 74 | 18 | 0.703 | 0.611 | 26.00 | 25.70 | 55.20 | 116.20 | 51.00 | 78.60 | 0.473 | 0.333 | 6 | 66.0 | 65.9 |
| Munoz-Esquerre [19] | 2016 | Nested | Hospital | Spain | NA | GOLD | JIS (2009) | 17 | 14 | 0.941 | 0.929 | 24.00 | 27.10 | 62.00 | 97.70 | 54.90 | 76.30 | 0.353 | 0.786 | 6 | 63.4 | 58.3 |
| Bozek [20] | 2016 | Cross-sectional | Population | Poland | Yes | GOLD | ICD-10 | 1084 | 1076 | 0.680 | 0.410 | 21.40 | 31.30 | 66.30 | 90.30 | NA | NA | 0.251 | 0.136 | 8 | 66.5 | 68.6 |
| Acharyya (ATP III) [21] | 2016 | Cross-sectional | Population | India | Yes | GOLD | ATP III | 77 | 77 | 0.740 | 0.740 | 23.00 | 24.00 | NA | NA | NA | NA | 0.442 | 0.312 | 7 | 60.0 | 60.0 |
| Acharyya (IDF) [21] | 2016 | Cross-sectional | Population | India | Yes | GOLD | IDF | 77 | 77 | 0.740 | 0.740 | 23.00 | 24.00 | NA | NA | NA | NA | 0.312 | 0.325 | 7 | 60.0 | 60.0 |
| Chung (Male) [22] | 2015 | Nested | Population | Korea | NA | GOLD | ATP III | 760 | 2346 | 1.000 | 1.000 | 23.50 | 24.30 | 77.10 | 96.30 | NA | NA | 0.295 | 0.264 | 6 | 64.5 | 53.2 |
| Chung (Female) [22] | 2015 | Nested | Population | Korea | NA | GOLD | ATP III | 279 | 3731 | 0.000 | 0.000 | 23.30 | 24.10 | 75.70 | 98.50 | NA | NA | 0.380 | 0.320 | 6 | 64.5 | 55.4 |
| Park [23] | 2014 | Cross-sectional | Population | U.S.A. | NA | GOLD | JIS (2009) | 94 | 3661 | 0.447 | 0.511 | 26.98 | 29.30 | 67.00 | 96.00 | 58.00 | 76.00 | 0.575 | 0.536 | 6 | 62.1 | 56.6 |
| Breyer [24] | 2014 | Cross-sectional | Population | Netherlands | NA | GOLD | IDF | 228 | 156 | 0.590 | 0.450 | 26.20 | 27.30 | 52.80 | 120.40 | 40.90 | 78.10 | 0.570 | 0.400 | 6 | 63.7 | 60.1 |
| Ozgen [25] | 2013 | Cross-sectional | Population | Turkey | Yes | GOLD | IDF | 50 | 40 | 0.900 | 0.850 | 27.20 | 27.60 | 46.30 | NA | 53.00 | NA | 0.440 | 0.300 | 8 | 61.3 | 58.4 |
| Hosny [26] | 2013 | Cross-sectional | Hospital | Egypt | Yes | GOLD | ATP III | 50 | 35 | 0.880 | 0.914 | 27.00 | 28.00 | 54.30 | NA | 62.20 | NA | 0.400 | 0.171 | 7 | 57.7 | 55.9 |
| Park (Male) [27] | 2012 | Nested | Population | Korea | NA | GOLD | ATP III | 100 | 437 | 1.000 | 1.000 | 23.30 | 24.10 | NA | NA | NA | NA | 0.330 | 0.222 | 6 | 60.9 | 50.8 |
| Park (Female) [27] | 2012 | Nested | Population | Korea | NA | GOLD | ATP III | 33 | 645 | 0.000 | 0.000 | 24.20 | 24.10 | NA | NA | NA | NA | 0.485 | 0.296 | 6 | 59.2 | 51.4 |
| Akpinar [28] | 2012 | Nested | Hospital | Turkey | Yes | GOLD | ATP III | 91 | 42 | 0.857 | 0.833 | NA | NA | NA | NA | NA | NA | 0.446 | 0.171 | 7 | 63.7 | 62.8 |
| Lam (Male) [29] | 2010 | Nested | Population | China | NA | GOLD | IDF | 128 | 1880 | 1.000 | 1.000 | NA | NA | NA | NA | NA | NA | 0.226 | 0.198 | 6 | 67.1 | 63.5 |
| Lam (Female) [29] | 2010 | Nested | Population | China | NA | GOLD | IDF | 368 | 4982 | 0.000 | 0.000 | NA | NA | NA | NA | NA | NA | 0.226 | 0.198 | 6 | 62.7 | 60.7 |
| Funakoshi [12] | 2010 | Cross-sectional | Population | Japan | NA | GOLD | ATP III | 297 | 6544 | 1.000 | 1.000 | 22.70 | 23.70 | 89.00 | 95.80 | 66.10 | 79.50 | 0.168 | 0.258 | 6 | 62.3 | 55.9 |
| Watz [13] | 2009 | Cross-sectional | Hospital | Germany | NA | GOLD | IDF | 57 | 30 | 0.719 | 0.767 | 27.80 | 27.50 | 63.00 | 99.60 | 53.20 | 75.00 | 0.526 | 0.533 | 5 | 63.3 | 62.6 |
| Marquis (Male) [11] | 2005 | Cross-sectional | Hospital | Canada | Yes | ATS (1987) | ATP III | 23 | 20 | 1.000 | 1.000 | 29.00 | 30.00 | NA | NA | NA | NA | 0.609 | 0.200 | 8 | 66.0 | 63.0 |
| Marquis (Female) [11] | 2005 | Cross-sectional | Hospital | Canada | Yes | ATS (1987) | ATP III | 15 | 14 | 0.000 | 0.000 | 27.00 | 29.00 | NA | NA | NA | NA | 0.267 | 0.214 | 8 | 66.0 | 63.0 |
Abbreviations: ATP-III, the Adult Treatment Panel III; ATS (1987), American Thoracic Society in 1987; BMI, body mass index; COPD, chronic obstructive pulmonary disease; FEV1, forced expiratory volume in one second; FVC, forced vital capacity; IDF, International Diabetes Federation; JIS (2009), a joint interim statement in 2009 (Circulation 2009; 120:1640–1645); MetS, metabolic syndrome; NA, not available; NOS, Newcastle–Ottawa Scale.