Table 2.
Background characteristics and data collection of the included case-control studies
| Reference | Region | Time frame of study | Design of study | Gender | Age, years [mean (standard deviation) or range] | Health outcome as defined in the manuscript | Definition of cancer cases | No of cases | No of controls | Total | Definition of dental visits | Adjusted covariates | Quality assessment |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chen et al. [44] | China | 2010–2015 | CCH | F | 20–80 | OCs (not defined) | Incident cases confirmed by histology | 250 | 996 | 1246 | Never, < once a year, ≥ once a year | Age, marital status, residence, family history of cancer, passive smoking, exposure to cooking oil fumes, and diet containing vegetablesand fruit | Strong |
| Mazul et al. [34] | North Carolina | 2002–2006 | CCP | M + F | 20–80 | HNCs (oral cavity, pharynx or larynx) | Diagnosed cases | 491 | 1396 | 1887 | Yes or no | Age, gender & race | Strong |
| Hashim et al. [20] | United States, Central Europe, Latin America, Japan & Asia | 2001–2009 | CCH | M + F | < 40–≤ 75 | HNCs (oral cavity, larynx, oropharynx, and hypopharynx) | Incident cases | 3551 | 2748 | 6299 | ≥ Once a year versus < than once a year | Age, center, sex, education, alcohol consumption, and tobacco smoking | Strong |
| Laprise et al. [45] | India (Kerala) | 2008–2012 | CCH | M + F | Mcases = 60.1 (10.8), Mcontrols = 59.2 (11.3), Fcases 59.8 (11.5), Fcontrols = 59.9 (12.1) | OCs (lip, tongue, gum, mouth, and palate) | Incident cases | 350 | 371 | 721 | Never, only when in pain, regularly | NA | Strong |
| Friemel et al. [21] | Germany | 2002–2005 | CCP | M + F | 32–77 | HNCs (tongue, gum, mouth, palate, tonsils, pharynx, and larynx | Incident cases diagnosed by pathology | 276 | None | 276 | At least once a year, every 2–5 years, less than every 5 years, never | NA | Strong |
| Dholam and Chouksey [46] | India | NG | CCH | M + F | 18–45 | OCs (lip, buccal mucosa, lower alveolus, retromolar trigone, oral tongue, floorof mouth, upper alveolus, and hard palate) and oropharynx | Incident cases | 85 | 85 | 170 | Every six months, once a year, less than once a year | NA | Strong |
| Huang J et al.[47] | China | 2010–2015 | CCP | M + F | > 20 | OCs (not defined) | Incident cases diagnosed by pathology | 414 | 870 | 1284 | Never, < 5 years, ≥ 5 years | Age, gender, body mass index, occupation, education, and place of residence | Strong |
| Tsai et al. [48] | Taiwan | 2010–2013 | CCH | M + F | 20–80 | HNCs (oral cavity, oropharynx, hypopharynx, and larynx) | Incident cases diagnosed by pathology | 436 | 514 | 950 | No, every 6 months or less, every 6–12 months | Age, sex, education, cigarette smoking (pack-year categories), betel-quid chewing (pack-year categories) and alcohol drinking (frequency) | Strong |
| Ahrens et al.[22] | European countries: Prague, Bremen, Athens, Aviani\o, Padova, Turin, Dublin, Oslo, Glassgow, Manchester, New castke, Barcelona, Zagreb | 2002–2005 | CCPH | M + F | Cases = 59.8(10.1), controls = 59.8(11.8) | UADTCs (oral cavity, oropharynx, hypopharynx, larynx, or esophagus) | Incident cases | 1963 | 1933 | 3896 | Never, at least once a year, 2–5 years, less than every 5 years | Age, sex, study center, smoking status, cumulative tobacco consumption, cumulative alcohol consumption, professional education, consumption of fruits and vegetables | Strong |
| Narayan et al.[49] | India | NG | CC | M + F | 21–≤ 80 | OCs (buccal mucosa, tongue, gingivo-buccal sulcus, and retromolar area) | Incident cases diagnosed by histopathology | 242 | 254 | 496 | 1–2 visits a year, 3–5 visits a year, > 5 visits a year | NG | Weak |
| Moergal et al.[23] | Rhineland-Palate, Germany | 2011–2012 | CCH | M + F | 37–88 | OCs (proximal to gingiva and mandibular/maxillary alveolar mucosa), floor of the mouth, tongue alveolar bone of maxilla and mandible, palate, cheek, and other locations of the mouth) | Incident cases identified from medical records | 178 | 123 | 301 | ≤ 6 months versus > 6 months | NG | Moderate |
| Eliot et al.[35] | Boston, United States | 2006–2011 | CCP | M + F | ≤ 18 | HNCs (oral cavity, pharynx and larynx) | Incident cases | 513 | 567 | 1080 | Less than every year, at least once a year | Age, race, sex, pack-years smoked, average alcoholic drinks per week, education status, and income level | Strong |
| Chang et al. [50] | Taiwan | 2010–2012 | CCH | M + F | 20–80 | HNCs (cavity, oropharynx, hypopharynx, and larynx) | Incident cases diagnosed by histopathology | 317 | 296 | 613 | Every 6 months or less, every 6–12 months, no | Age, sex, education, cigarette smoking (pack-year categories) and betel quid chewing (pack-year categories), and alcohol drinking (frequency) | Strong |
| Macfarlane et al. [24] | Europe | 2002–2005 | CCP | M + F | < 50 | UADTCs (lip, tongue, gum, mouth, and palate), pharynx, larynx, and esophagus | Incident cases | 356 | 419 | 775 | Never, < every 5 years, every 2–5 years, at least every year | Age, gender, education, center, smoking, and alcohol consumption | Strong |
| Johnson et al.[36] | Eastern Ontario region, Canada | 2004–2005 | CCH | M + F | ≥ 35 | HNCs (oral cavity, larynx, hypopharynx, and oropharynx) | Incident cases and patients diagnosed with cancer within 2 years of the date of interview | 162 | 2679 | 2841 | At least every 12 months, less than once a year, rarely, or never | Age, gender, education, immigrant status, and smoking | Strong |
| Divaris et al. [18] | 46 counties of North Carolina | 2002–2006 | CCP | M + F | 26–80 | HNCs (oral, pharyngeal, and laryngeal) | Incident cases | 1289 | 1361 | 2650 | Yes or No | Age, sex, race, education, smoking status intensity, drinking status, cumulative ethanol consumption, fruit and vegetable consumption | Strong |
| Marques et al.[39] | São Paulo, southeastern Brazil | 1998–2002 | CCH | M + F | < 40–≥ 70 | OCs (lip, tongue, gum, mouth, and palate) and pharynx (tonsil and oropharynx) | Incident cases diagnosed by histopathology | 309 | 468 | 777 | Regular (annually) occasional (interval between visits ≥ 2 years), never | Age, sex, schooling, smoking, alcohol consumption, and all other oral health/hygiene variables | Strong |
| Guha et al. [40] | Latin America | 1998–2003 | CCPH | M + F | < 40–≥ 70 | HNCs (oral cavity, pharynx and larynx) | Incident cases confirmed by histology or cytology | 2423 | 1824 | 4247 | Every year, every 2–5 years, less than every 5 years, never | Age, sex, center, education, tobacco pack-years, cumulative alcohol consumption, and all other oral health variables | Strong |
| Rosenquist et al. [25] | Southern health care region of Sweden | 2000–2004 | CCP | M + F | 33–89 | OCs (tongue, floor of mouth) and oropharynx | Cancer cases identified from ear nose and throat department | 165 | 320 | 485 | Regular versus no | Tobacco and alcohol consumption | Strong |
| Guneri et al. [26] | Turkey | 1998–2002 | CCPH | M + F | Mean for cases = 56.26, for controls = 53.39 | OCs (lip, tongue, floor of the mouth and gingiva, buccal mucosa, hard and soft palate) | Incident cases identified from ear nose and throat department | 79 | 61 | 140 | Frequent, not frequent | NG | Moderate |
| Lissowska et al. [27] | Warsaw, Poland | 1997–2000 | CCH | M + F | 23–80 | OCs (tongue, gum, and mouth) and oropharynx | Incident cases diagnosed by histology | 122 | 124 | 246 | Never versus visits at least once a year | Age, gender, place of residence, smoking, and drinking habits | Strong |
| Balram et al.[52] | Southern India (Bangalore, Madras and Trivandarum) | 1996–1999 | CCH | M + F | 22–85 | OCs (not defined) | Incident cases identified from 3 South Indian centers | 591 | 582 | 1173 | Never versus yes | Age, center, education, smoking, and drinking habits for men only | Strong |
| Garrote et al. [41] | Cuba | 1996–1999 | CCH | M + F | 28–91 | OCs (mouth) and oropharynx | Incident cases identified from National institute | 200 | 200 | 400 | Never, ≥ once every five years, < once every 5 years | Age, gender, area of residence, education, smoking, and drinking habits | Strong |
| Winn et al.[42] | Puerto Rico | 1992–1995 | CCP | M + F | 21–79 | OCs (tongue, gum, mouth) and pharynx (oropharynx and hypopharynx) | Incident cases diagnosed by histology | 342 | 521 | 863 | Yes, no, never | NG | Strong |
| Moreno-Lopez et al.[54] | Spain | Not mentioned | CCH | M + F | 19–85 | OCs (labial mucosa, tongue, gingiva, mouth) and oropharynx | Hospital diagnosed cases | 75 | 150 | 225 | Never, not regularly (at least once a year), regularly | NG | Strong |
| Talamini et al.[28] | Italy | 1996–1999 | CCH | M + F | 27–86 | OCs (tongue, mouth,) and oropharynx | Incident cases | 132 | 148 | 280 | Never, < once a year, ≥ once a year | Age, gender, fruit and vegetable intake, and smoking &drinking habits | Strong |
| Bundgaard et al.[29] | Denmark | 1986–1990 | CCP | M + F | ≤ 45–> 70 | OCs (retromolar area, buccal mucosa, floor of mouth, hard palate, upper and lower alveolus, and tongue) | Incident cases | 161 | 483 | 644 | At least once a year (regularly), more than once year | Tobacco and alcohol | Strong |
| Maier et al. [30] | Germany | 1986–1989 | CCH | M + F | 30–75 | HNCs (oral-cavity, oropharynx, hypopharynx and larynx) | Cases examined at department of maxillo-facial and head and neck surgery | 100 | 214 | 314 | Only in pain, less than once a year, more than once a year | NG | Moderate |
| Marshall et al.[37] | New York | 1975–1983 | CCP | M + F | ≤ 50–≥ 76 | HNCs (tongue, oropharynx, floor of mouth, pharynx, or hypopharynx) | Cases diagnosed pathologically | 290 | 290 | 580 | White patches, infection or inflammation, sharp or jagged teeth, toothache or crooked teeth | Tobacco and alcohol | Moderate |
| Zheng et al.[51] | China | 1989–1990 | CCH | M + F | 18–80 | OCs (tongue and mouth) | Incident cases diagnosed by histology | 404 | 404 | 808 | Routine visits or because of oral ulceration and toothache | NG | Strong |
| Franco et al.[43] | Brazil | 1986–1988 | CCH | M + F | < 40–≥ 70 | OCs (tongue, gum, and mouth) | Incident cases diagnosed by histopathology | 232 | 464 | 696 | Never, < once a year, ≥ once a year | Age, sex, study site, and admission period | Strong |
| Elwood et al. [2] | Canada | 1977–1980 | CCH | M + F | 20–94 | HNCs (tongue, mouth, oropharynx, hypo-pharynx, and larynx) | Incident cases | 374 | 374 | 748 | No regular dental care versus no special dental care | Socioeconomic status, marital status, alcohol, and cigarette consumption | Strong |
CCH case-control with hospital based controls, CCP case-control with population based controls, CCPH case-control with hospital- and population-based controls, M males, F females, M + F males and females, NG not given, OCs oral cancers, HNCs head and neck cancers, UADTCs upper aerodigestive tract cancers