Table 1.
Characteristics of the study included in the meta-analysis
| Author | Country | Study design | Sample size | Age/sex | Outcome | Duration |
|---|---|---|---|---|---|---|
| Kabatetal., 1989[16] | NewYork | Case-control study | Cases-125 Control-107 | - | Oral cancer | 4 years |
| Zhengetal.,1990[17] | Beijing, China | Case-control study | Cases-404 controls-404 | 18-80 years | Oral cancer | 1 year |
| Bundgaardetal., 1995[18] | Denmark | Case-control study | Cases-161 Controls-483 | Below 75 years | Oral cancer | 4 years |
| Garroteetal., 2001[19] | Cuba | Case-control study | Cases-200 Control-200 | 25-88 years | Oral cancer | 3 years |
| Balarametal., 2002[20] | India | Case-control study | Cases-590 Control-582 | 18-80 years | Oral cancer | 3 years |
| Lissowskaetal., 2003[21] | Poland | Case-control study | Cases-122 Control-124 | 23-80 years | Oral cancer | 3 years |
| Rosenquistetal., 2005[22] | Southern Sweden | Case-control study | Cases-132 Controls-320 | Male-36/87 years Female-33/87 years | Oral cancer | 4 years |
| Hirakietal., 2008[23] | Japan | Case-control study | Cases-5240 Control-10,480 | 1879 years | Oral cancer | 5 years |
| Tezaletal., 2009[24] | NewYork | Case-control study | Cases-266 Control-207 | - | Oral cancer | 6 years |
| Changetal., 2013[25] | Taiwan | Case-control study | Cases-212 Control-296 | 20-80 years | Oral cancer | 2 years |
| Narayanetal., 2014[26] | India | Case-control study | Cases-242 Controls-254 | - | Oral cancer | - |
| Chenetal., 2017[27] | Fujian China | Case-control study | Cases-250 Control-996 | Oral cancer | 5 years | |
| Hashimetal., 2016[28] | NewYork | Case-control study | Cases-8925 Control-12,527 | Above 40 years age | Oral cancer | - |
| Guptaetal., 2017[29] | India | Case-control study | Cases-187 Control-240 | 30-80 years | Oral cancer | 1 year |
| Kawakitaetal., 2017[30] | China | Case-control study | Cases-921 Control-806 | 18-80 years | Oral cancer | 5 years |