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Table 2 Background characteristics and data collection of the included case-control studies

From: Evidence of past dental visits and incidence of head and neck cancers: a systematic review and meta-analysis

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
  1. 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