Table 1. Characteristics of the case–control studies included in the meta-analysis.
| Study | Country | Period of enrolment | Gender | Tumor type | No. of cases | No. of controls | Source of control | Variables adjusted for in the regression models |
|---|---|---|---|---|---|---|---|---|
| Bandurska 2011 [34] | Europe | 1994-2003 | WM | TC | 297 | 589 | Pop | Matched on age and place of residence. |
| Choi 2013 [35] | Asia | 2010-2011 | WM | TC | 71 | 12141 | Pop | Age, occupation, household income, marital status, BMI, and smoking. |
| Franceschi 1989 [36] | Europe | 1984-1986 | WM | TC | 245 | 411 | Hos | Matched on age, sex and geographical area. |
| Galanti 1997 [37] | Europe | 1993-1994 | WM | DTC | 246 | 440 | Pop | Matched on age, gender, and county of residence. |
| Guignard 2007 [18] | Europe | 1993-1999 | WM | DTC | 332 | 412 | Pop | Age, ethnic group, and smoking. |
| Kolonel 1990 [38] | America | 1980-1987 | WM | DTC | 191 | 441 | Pop | Age, gender, ethnicity, education, marital status, smoking, height, weight, occupation, radiation exposure. |
| Lence-Anta 2014 [39] | America | 2000-2011 | WM | DTC | 203 | 212 | Pop | Age, gender, smoking status, ethnic group, education, number of pregnancies in women, height, and BMI. |
| Mack 2002 [19] | America | 1980-1983 | W | TC | 292 | 292 | Pop | Age, race, and prior benign thyroid disease. |
| Menezes 2015 [20] | America | 2000-2009 | WM | TC | 4023 | 24840 | Hos | Age, gender, race, education, marital status, smoking habits, region of residence, and year of diagnosis. |
| Nagano 2007 [40] | Asia | 1970-1986 | WM | DTC | 362 | 362 | Pop | Age, sex, city, and radiation dose, family history of cancer and past history of goiter or thyroid nodule, smoking. |
| Prestonmartin 1987 [41] | America | 1980-1981 | W | TC | 110 | 110 | Pop | Matched on age and place of residence. |
| Riza 2015 [42] | Europe | 1990-1993 | WM | TC | 113 | 138 | Hos | Matched on age, sex, health unit. |
| Ron 1987 [43] | America | 1978-1980 | WM | TC | 159 | 285 | Pop | Age, sex, prior radiotherapy to the head and neck, thyroid nodules, and goiter. |
| Rossing 2000 [44] | America | 1988-1994 | W | PTC | 410 | 574 | Pop | Matched on age and county of residence |
| Stansifer 2015 [45] | America | WM | TC | 467 | 225 | Pop | None | |
| Takezaki 1996 [46] | Asia | 1988-1993 | W | DTC | 94 | 22666 | Hos | Age and year of visit. |
| Xhaard 2014 [47] | Europe | 1981-2003 | WM | DTC | 229 | 373 | Pop | Age, height, BMI, number of pregnancies and menopausal status in women, familial history of thyroid cancer, educational level, medical or therapeutic irradiation of the neck |
Abbreviation: W, Women; WM, Women + Men; TC, thyroid cancer; DTC, differentiated thyroid cancer; PTC, papillary thyroid cancer; Pop, population-based; Hos, hospital-based; BMI, body mass index.