Table 3

Estimated effects of marijuana use (OR and 95% CI) on the risk of head and neck cancer for individuals <55 years by covariates selected for adjustmenta

No. of casesNo. of controlsCovariates
No. of covariates (crude)Pack-years of smokingPack-years of smoking plusb
Marijuana use
 Never35511.01.01.0
 Ever20122.4 (1.1–5.6)2.7 (1.02–6.9)3.1 (0.99–9.7)
Times/day
 Continuous1.4 (0.95–2.1)1.4 (0.9–2.2)1.5 (0.9–2.5)
 035511.01.01.0
 1742.6 (0.7–9.4)1.9 (0.5–7.8)3.7 (0.7–20.9)
 >1725.1 (1.0–26)5.9 (1.03–34)6.9 (0.9–50.3)
P for trend0.02190.03440.0285
Times/dayb
 Continuous1.4 (0.95–2.1)1.4 (0.9–2.3)1.4 (0.9–2.3)
 035511.01.01.0
 113101.9 (0.7–4.8)2.0 (0.7–5.8)2.4 (0.7–8.6)
 >1725.1 (1.0–26)5.9 (1.04–34)5.9 (0.9–39.9)
P for trend0.02240.02540.0376
Years of use
 Continuous1.1 (1.0–1.2)1.1 (0.99–1.2)1.1 (0.98–1.2)
 035511.01.01.0
 1–5742.6 (0.7–9.4)3.0 (0.7–12.3)7.0 (1.2–39.2)
 >51052.9 (0.92–9.3)3.6 (0.9–14.1)3.3 (0.7–16.5)
P for trend0.03800.03500.0548
Years of useb
 Continuous1.1 (1.0–1.2)1.1 (0.99–1.2)1.1 (0.98–1.2)
 035511.01.01.0
 1–51072.1 (0.7–6.0)2.2 (0.7–6.9)3.2 (0.8–12.9)
 >51052.9 (0.92–9.3)3.6 (0.9–14.1)3.0 (0.6–13.7)
P for trend0.03800.04090.0791
  • a Also 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).

  • b Missing data were replaced by median.