Table 1. Characteristics of the included studies.
| Study | Sample size | Region | Resource | Matched/adjusted for | Marital status (%) | NOS score | |||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Total | Cases | Case | Control | Married | Widowed | Divorced | Lifelong single | ||||
| Cohort studies | |||||||||||
| Carlsen et al. [11] | 1,590,000 | 25,855 | Europe | population | population | multiple variables | N/A | N/A | N/A | N/A | 7 |
| Melchior et al. [13] | 5493 | 120 | Europe | employees | employees | multiple variables | N/A | N/A | N/A | N/A | 7 |
| Case-control studies | |||||||||||
| Adami et al. [21] | 358 | 179 | Europe | population | population | age | 60.3 | 24.9 | 4.2 | 10.6 | 6 |
| Balekouzou et al. [22] | 519 | 174 | Africa | hospital | hospital | multiple variables | 14.3 | 85.7 (w/d/lls) | 6 | ||
| Bano et al. [23] | 1246 | 1238 | Asia | hospital | hospital | multiple variables | N/A | N/A | N/A | N/A | 4 |
| Budiningsih et al. [24] | 900 | 300 | Asia | hospital | hospital | multiple variables | N/A | N/A | N/A | N/A | 5 |
| Cho et al. [25] | 705 | 358 | Asia | hospital | screening | age | 81.8 | 13.3 (w/d) | 4.8 | 5 | |
| Dey et al. [26] | 2108 | 900 | Asia | hospital | companion | multiple variables | 83.2 | N/A | 14.9 | 1.9 | 5 |
| Dianatinasab et al. [27] | 1052 | 526 | Asia | hospital | hospital | multiple variables | 92.8 | N/A | N/A | 7.2 | 7 |
| Ebrahimi et al. [28] | 535 | 286 | Asia | hospital | hospital | multiple variables | 77.4 | 16.8 (w/d) | 5.8 | 4 | |
| Ewertz et al. [14] | 3520 | 1782 | Europe | population | population | age | 73.9 | 10.6 | 8.8 | 6.6 | 6 |
| Faheem et al. [29] | 300 | 150 | Asia | hospital | population | age | 92.3 | 7.7 (w/d/lls) | 3 | ||
| Forsen [30] | 174 | 87 | Europe | hospital | hospital | multiple variables | N/A | N/A | N/A | N/A | 4 |
| Gajalakshmi and Shanta [31] | 1062 | 293 | Asia | hospital | hospital | multiple variables | 96.5 | 3.5 (w/d/lls) | 4 | ||
| Ghiasvand et al. [32] | 1042 | 521 | Asia | hospital | hospital | multiple variables | 84.0 | 6.9 (w/d) | 9.1 | 5 | |
| Gilani and Kamal [33] | 1480 | 498 | Asia | hospital | population | age | 96.6 | 3.4 (w/d/lls) | 6 | ||
| Hadjisavvas et al. [34] | 2282 | 1109 | Europe | population | population | multiple variables | 84.8 | 10.8 (w/d) | 4.3 | 7 | |
| Jafari-Mehdiabad et al. [35] | 285 | 98 | Asia | hospital | hospital | multiple variables | 84.2 | 11.9 | 1.8 | 2.1 | 5 |
| Justenhoven et al. [36] | 1997 | 1021 | Europe | population | population | multiple variables | 68.0 | 26.7 (w/d) | 5.3 | 5 | |
| Khalis et al. [37] | 474 | 237 | Africa | hospital | hospital | age | 68.8 | 12.2 | 8.2 | 10.8 | 6 |
| Khan et al. [38] | 196 | 100 | Asia | hospital | population | age | 84.2 | 15.8 (w/d/lls) | 4 | ||
| Kvikstad et al. [12] | 45,685 | 4491 | Europe | population | population | multiple variables | 83.6 | 2.9 | 13.4 | N/A | 7 |
| Laing et al. [39] | 992 | 503 | USA | hospital | hospital | multiple variables | 38.3 | 40.3 (w/d) | 21.4 | 5 | |
| Li et al. [40] | 1982 | 975 | USA | population | population | age | 53.1 | 31.1 | 12.4 | 3.4 | 4 |
| Lotfi and Shobairi [41] | 159 | 80 | Asia | hospital | population | age | 88.1 | 11.9 (w/d/lls) | 5 | ||
| Mahouri et al. [42] | 672 | 168 | Asia | hospital | hospital | age | 82.3 | 13.8 (w/d) | 3.9 | 4 | |
| Marzouk et al. [43] | 351 | 198 | Europe | hospital | hospital | age | 74.6 | 18.8 | 5.1 | 1.4 | 5 |
| Mohite et al. [44] | 434 | 217 | Asia | hospital | hospital | multiple variables | 85.0 | 10.6 | 2.3 | 2.1 | 4 |
| Morales et al. [45] | 1084 | 465 | USA | hospital | hospital | multiple variables | 61.1 | 6.5 | 20.2 | 12.3 | 6 |
| Motie et al. [46] | 254 | 134 | Asia | population | population | age | 97.2 | 2.8 (w/d/lls) | 4 | ||
| Oran et al. [47] | 1244 | 622 | Europe | hospital | hospital | multiple variables | 81.3 | N/A | N/A | 6.0 | 5 |
| Pakseresht et al. [48] | 332 | 115 | Asia | hospital | hospital | age | 80.1 | 19.9 (w/d/lls) | 5 | ||
| Parameshwari et al. [49] | 100 | 20 | Asia | population | population | multiple variables | 95.0 | 5.0 (w/d/lls) | 4 | ||
| Peled et al. [50] | 622 | 255 | Europe | hospital | hospital | multiple variables | 72.7 | 20.9 (w/d/lls) | 4 | ||
| Pimhanam et al. [51] | 888 | 444 | Asia | hospital | population | age | 67.5 | 10.0 (w/d) | 22.5 | 4 | |
| Price et al. [52] | 504 | 239 | Australia | suspicion | suspicion | age | 68.5 | 12.5 | 12.1 | 6.9 | 4 |
| Rao et al. [53] | 1400 | 689 | Asia | hospital | hospital | multiple variables | 76.4 | 20.6 | 0.6 | 2.4 | 4 |
| Rookus and van Leeuwen [54] | 1836 | 918 | Europe | population | population | multiple variables | 88.1 | 11.9 (w/d/lls) | 5 | ||
| Shamsi et al. [55] | 883 | 297 | Asia | hospital | hospital | multiple variables | N/A | N/A | N/A | N/A | 6 |
| Shaukat et al. [56] | 94 | 42 | Asia | hospital | hospital | age | 97.9 | 2.1 (w/d/lls) | 4 | ||
| Sufian et al. [57] | 216 | 108 | Asia | hospital | hospital | age | 93.5 | 6.5 (w/d/lls) | 4 | ||
| Tazhibi et al. [58] | 257 | 216 | Asia | relatives | relatives | multiple variables | 94.2 | 5.8 (w/d/lls) | 5 | ||
| Tehranian et al. [59] | 624 | 312 | Asia | hospital | hospital | multiple variables | 83.8 | N/A | 1.6 | 14.6 | 4 |
| Thompson et al. [60] | 1076 | 541 | USA | hospital | screening | age | 60.9 | 39.1 (w/d/lls) | 5 | ||
| Wakai et al. [61] | 678 | 226 | Asia | hospital | hospital | multiple variables | 78.3 | 17.3 | 3.7 | 0.7 | 4 |
| White et al. [62] | 1607 | 747 | USA | population | population | multiple variables | 73.0 | 15.8 (w/d) | 11.2 | 7 | |
| Yan et al. [63] | 1042 | 521 | Asia | hospital | hospital | age | 93.5 | 6.5 (w/d/lls) | 6 | ||
| Eaker et al. [64] | 28566 | 4761 | Europe | population | population | multiple variables | 62.9 | 2.9 | 17.8 | 16.8 | 8 |
| Randi et al. [65] | 14429 | 5856 | Europe | hospital | hospital | multiple variables | N/A | N/A | N/A | N/A | 7 |
N/A: not applicable.