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Table 6 Effect estimates for never smokersa

From: Meta-analysis of the relation between European and American smokeless tobacco and oral cancer

Study First author, year of publication Adjustment factors Exposure Sex Exposed cases OR/RR (95%CI)
Studies providing result specific for oral cancer
8 Keller
1970 [75]
None Smokeless M 4 3.04 (0.62–14.99)
16 Blot
1988 [100]
Age, race, location, respondent Smokeless F 6 6.20 (1.90–19.80)
19 Blomqvist
1991 [103]
None Snuff M+F 2 0.67 (0.08–5.75)
25 Kabat
1994 [59]
None Smokeless M 4 1.59 (0.51–4.96)
     F 4 38.7 (2.1–723.6)b
29 Schildt
1998 [73]
Age, sex, residence Snuff M+F 19 0.70 (0.40–1.20)
32 Henley
2005 [66]
Age, race, education, alcohol, exercise, aspirin, body mass index, diet, occupationc Smokeless M (CPS-I) 4 2.02 (0.53–7.74)
     M (CPS-II) 1 0.90 (0.12–6.71)
   Fixed-effect meta-analysis estimate for six studies 1.30 (0.87–1.93)
   Random-effects meta-analysis estimate for six studies 1.94 (0.88–4.28)
   Heterogeneity χ2 (df) 18.99 (7)
    p 0.0082
    I2 63.13
Additional study providing result for oral, larynx and oesophagus cancer combined
27 Lewin
1998 [64]
Age, region Snuff M 9 4.70 (1.60–13.80)
   Fixed-effect meta-analysis estimate for all seven studies 1.51 (1.04–2.19)
   Random-effect meta-analysis estimate for all seven studies 2.20 (1.04–4.67)
   Heterogeneity χ2 (df) 23.82 (8)
    p 0.0025
    I2 66.42
  1. aSee the discussion section for the reasons why data from study 15 [65] were not included in Table 6
  2. b There were no exposed controls and the OR was estimated by adding 0.5 to each cell in the 2 × 2 table
  3. cOccupation only adjusted for in CPS-II