Tobacco smoking is a known cause of gastric cancer, but
several aspects of the association remain imprecisely
quantified. We examined the relation between cigarette
smoking and the risk of gastric cancer using a uniquely large
dataset of 23 epidemiological studies within the ‘Stomach
cancer Pooling (StoP) Project’, including 10 290 cases and
26 145 controls. We estimated summary odds ratios (ORs)
and the corresponding 95% confidence intervals (CIs) by
pooling study-specific ORs using random-effects models.
Compared with never smokers, the ORs were 1.20 (95% CI:
1.09–1.32) for ever, 1.12 (95% CI: 0.99–1.27) for former, and
1.25 (95% CI: 1.11–1.40) for current cigarette smokers. Among
current smokers, the risk increased with number of cigarettes
per day to reach an OR of 1.32 (95% CI: 1.10–1.58) for
smokers of more than 20 cigarettes per day. The risk
increased with duration of smoking, to reach an OR of 1.33
(95% CI: 1.14–1.54) for more than 40 years of smoking and
decreased with increasing time since stopping cigarette
smoking (P for trend<0.01) and became similar to that of
never smokers 10 years after stopping. Risks were somewhat
higher for cardia than noncardia gastric cancer. Risks were
similar when considering only studies with information on
Helicobacter pylori infection and comparing all cases to
H. pylori+ controls only. This study provides the most precise
estimate of the detrimental effect of cigarette smoking on the
risk of gastric cancer on the basis of individual data, including
the relationship with dose and duration, and the decrease in
risk following stopping smoking