Overall 24% of control subjects were smokers, but
habit is much more common in men (64.1% of smokers
among controls) than among women (none). Ever smokers
had a 1.82-fold risk (95%CI=0.99-3.35, p-value=0.05) in
univariate analysis when compared with never smokers
and the risk increased with duration of smoking (P for
trend=0.02) (Table 2). There was a very strong dose-
response effect, with those smoking 10-20 pack-years
having a 2.86-fold (95%CI=1.10-7.42, p-value=0.02)
increased risk of developing oral cancer.