Table 4

Estimated combined effects (OR and 95% CI) of lifetime marijuana use (ever versus never) and each of three potential modifiers (cigarette smoking, heavy alcohol use, and mutagen hypersensitivity) on the risk of head and neck cancers by covariates selected for adjustment

Potential modifierMarijuana useNo. of casesNo. of controlsCovariates
No. of covariates (crude)Pack-years of smokingPack-years smoking plusa
Smoking history
 NeverNever26561.01.01.0
 QuitNever34621.2 (0.6–2.2)0.4 (0.2–0.99)0.4 (0.2–0.99)
 CurrentNever84374.9 (2.7–9.0)1.7 (0.7–3.7)1.8 (0.6–4.8)
 NeverYes250.9 (0.2–4.7)0.9 (0.2–4.7)0.7 (0.1–5.5)
 QuitYes891.9 (0.7–5.5)0.8 (0.3–2.7)2.1 (0.5–8.3)
 CurrentYes14215.1 (3.2–71)9.7 (1.1–83.5)18.8 (1.7–204)
Current smoking
 NoNever601181.01.01.0
 YesNever84374.5 (2.7–7.3)3.0 (1.7–5.3)3.6 (1.7–7.4)
 NoYes10141.4 (0.6–3.4)1.3 (0.5–3.2)2.6 (0.8–8.0)
 YesYes14213.8 (3.0–63)16.3 (2.0–131)36.1 (3.6–358)
Alcohol (drinks/month)
 <100Never901321.01.01.0
 ≥100Never51145.3 (2.8–10.2)4.1 (2.0–8.3)4.3 (2.0–9.3)
 <100Yes14151.4 (0.6–3.0)1.6 (0.7–3.8)2.7 (0.96–7.5)
 ≥100Yes1027.3 (1.6–34.3)5.9 (1.2–30.4)9.6 (1.6–56.8)
Mutagen sensitivity (breaks/cell)
 <1Never30911.01.01.0
 ≥1Never46285.0 (2.7–9.3)6.3 (2.9–13.4)6.1 (2.4–15.3)
 <1Yes692.0 (0.7–6.2)2.2 (0.5–9.4)1.1 (0.2–7.4)
 ≥1Yes10215.2 (3.1–73)15.6 (2.9–84)77.1 (7.2–826)
  • a Adjusted for age (continuous variable), gender (male = 0, female = 1); race (white = 0, non-white = 1); education (≤high school = 0; college = 1, >college = 2); heavy alcohol use (<100/month = 0, ≥100/month = 1); and passive smoking (no = 0, yes = 1).