Table 4

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

Passive smokingPotential modifierNo. of casesNo. of controlsNo covariates (crude)Pack-years of smokingPack-years smoking plusa
Cigarette smoking
NoNever3131.01.01.0
NoEver6141.9 (0.4–9.0)0.9 (0.2–4.9)0.4 (0.1–2.7)
YesNever23462.2 (0.6–8.4)2.2 (0.6–8.4)1.5 (0.3–6.5)
YesEver121925.7 (1.6–20.6)1.9 (0.5–7.4)1.4 (0.3–6.1)
Alcohol (drinks/month)
No<1006241.01.01.0
No≥1004116.0 (1.5–170)6.4 (0.5–83.5)4.9 (0.3–75.8)
Yes<100891183.0 (1.2–7.7)2.0 (0.8–5.4)2.5 (0.8–7.6)
Yes≥100511414.6 (5.0–42.6)7.8 (2.5–24.1)10.2 (2.7–37.8)
Mutagen sensitivity (breaks/cell)
No<13171.01.01.0
No≥1344.3 (0.6–29.5)2.9 (0.3–30.3)2.6 (0.1–71.1)
Yes<129782.1 (0.6–7.7)1.6 (0.3–8.8)2.0 (0.2–17.7)
Yes≥1462510.4 (2.8–39.1)11.6 (2.1–63.0)17.5 (1.9–162)
Marijuana use
NoNo5231.01.01.0
NoYes545.8 (1.1–29.4)3.6 (0.6–21.2)3.5 (0.4–28.4)
YesNo1261264.6 (1.7–12.5)3.1 (1.0–9.8)2.6 (0.7–9.0)
YesYes19136.7 (2.0–22.3)5.8 (1.5–22.8)7.1 (1.5–34.5)
  • a Also adjusted for age (continuous variable); gender (male, 0; female, 1); race (white, 0; non-white, 1); education (≤high school, 0; college, 2; >college, 2); heavy alcohol use (<100/month, 0; ≥100/month, 1); and marijuana use (no, 0; yes, 1).