Table 1.
The baseline characteristics of the included studies.
| No. | First author | Region | Study design | Sample size (male/female) | Age | Disease duration (year) | Duration of levodopa usage (year) | Score | ||
|---|---|---|---|---|---|---|---|---|---|---|
| PD | Control group | PD | Control group | |||||||
| 1 | Li et al. (2020) | China | case–control study | 322 (186/136) | 214 (108/106) | 64.5 ± 8.5 | 63.8 ± 9.3 | NA | NA | 7 |
| 2 | Chen et al. (2015) | China | cross-sectional study | 60 (34/26) | 50 (27/23) | 63.1 ± 10.6 | 55.6 ± 10.8 | NA | NA | 8 |
| 3 | Ozer et al. (2006) | turkey | cross-sectional study | 39 (25/14) | 28 (15/13) | 67.0 ± 9.3 | 61.9 ± 8.3 | 6.4 ± 3.9 | 4.4 ± 3.5 | 8 |
| 4 | Triantafyllou et al. (2008) | Athens | cross-sectional study | 111 (65/46) | 93 (NA) | 70.1 ± 8.0 | 69.6 ± 8.1 | 5.9 ± 3.9 | NA | 7 |
| 5 | Zoccolella et al. (2009) | Italy | cross-sectional study | 121 (72/49) | 154 (97/57) | 67.8 ± 8.0 | 68.7 ± 8.8 | NA | ≥ 1-y | 8 |
| 6 | Zoccolella et al. (2005) | Italy | case–control study | 45 (27/18) | 15 (NA) | 61.3 ± 9.0 | 61 ± 10.4 | 10.4 ± 6.2 | NA | 9 |
| 7 | Lamberti et al. (2005) | Italy | case–control study | 46 (33/13) | 32 (22/10) | 63.7 ± 8.9 | 64.5 ± 11.5 | 10.8 ± 5.0 | 7.2 ± 4.8 | 7 |
| 8 | Triantafyllou et al. (2007) | Athens | case–control study | 67 (37/30) | 67 (NA) | 69.9 ± 5.3 | NA | 7.3 ± 3.4 | YES | 6 |
| 9 | Saadat et al. (2018) | Babol | cross-sectional and case–control study | 100 (53/47) | 100 (50/50) | NA | NA | NA | NA | 5 |
| 10 | Białecka et al. (2012) | Poland | case–control study | 320 (164/156) | 254 (136/118) | 64.4 ± 10.1 | 64.8 ± 9.6 | 6.8 ± 5.2 | YES | 8 |
| 11 | Ojo et al. (2011) | South western Nigeria | cross-sectional study | 40 (32/8) | 40 (32/8) | 65.8 ± 9.8 | 63.3 ± 10.8 | 5.4 ± 0.81 | NA | 8 |
| 12 | Caccamo et al. (2007) | Italy | case–control study | 49 (22/27) | 86 (40/46) | 64.2 ± 7.5 | 64.1 ± 7.1 | 5.8 ± 4.1 | 4.8 ± 3.4 | 9 |
| 13 | Camicioli et al. (2009) | Canada | cross-sectional study | 51 (30/21) | 50 (29/21) | 71.5 ± 4.7 | 71.6 ± 4.9 | 8.74 ± 4.4 | YES | 8 |
| 14 | Gorgone et al. (2012) | Italy | case–control study | 60 (27/33) | 82 (37/45) | 64.5 ± 7.7 | 64.1 ± 7.2 | NA | ≥ 1-y | 8 |
| 15 | Lee et al. (2010) | Korea | cross-sectional study | 96 (42/53) | 285 (126/159) | 67.6 ± 6.0 | 67.6 ± 6.0 | 5.7 ± 2.7 | 3.3 ± 1.7 | 7 |
| 16 | Religa et al. (2006) | Poland | case–control study | 114 (NA) | 100 (NA) | 70.0 ± 7.6 | 71.2 ± 6.0 | 5.5 ± 4.0 | 4.8 ± 10.4 | 9 |
| 17 | Rodriguez-Oroz et al. (2009) | Spain | cross-sectional study | 89 (52/37) | 30 (16/14) | 71.7 ± 6.4 | 68.5 ± 3.0 | 14.3 ± 4.4 | YES | 8 |
| 18 | Sapkota et al. (2014) | Canada | cross-sectional study | 46 (26/20) | 49 (28/21) | 70.8 ± 4.3 | 71.6 ± 4.0 | 8.42 ± 4.51 | 4.78 ± 4.18 | 8 |
| 19 | Shin and Sohn (2009) | Korea | case–control study | 33 (10/23) | 41 (12/29) | 63.5 ± 7.8 | 65.4 ± 7.8 | ≥ 3-y | ≥ 3-y | 8 |
| 20 | Sławek et al. (2013) | Poland | cross-sectional study | 192 (101/91) | 184 (114/70) | 63.7 ± 9.4 | 65.4 ± 9.2 | 6.8 ± 5.3 | NA | 8 |
| 21 | Song et al. (2013) | Korea | cross-sectional study | 61 (26/35) | 48 (11/37) | 68.3 ± 7.0 | 66.2 ± 11.8 | 3.0 ± 2.4 | 2.7 ± 2.5 | 7 |
| 22 | Todorović et al. (2006) | Serbia | case–control study | 113 (63/50) | 53 (34/19) | 61.1 ± 9.1 | 60.8 ± 13.1 | 3.1 ± 2.5 | YES | 7 |
| 23 | Yuan et al. (2009) | China-Taiwan | case–control study | 76 (28/48) | 110 (37/73) | 71.4 ± 9.8 | 69.9 ± 8.5 | 5.0 ± 4.0 | 6.2 ± 4.3 | 8 |
| 24 | Wei et al. (2016) | China | cross-sectional study | 17 (11/6) | 85 (55/30) | 71.0 ± 15.4 | 70.7 ± 12.1 | NA | NA | 6 |
| 25 | Zou et al. (2018) | China | cross-sectional study | 92 (49/47) | 80 (44/36) | 65.7 ± 11.2 | 64.4 ± 7.1 | 4.1 ± 3.4 | YES | 7 |
NA: not available.