Prospective study on the relation of cigarette smoking with cancer of the liver and stomach in an endemic region.
BACKGROUND
Smoking has not been confirmed as a risk factor for cancers of the liver and stomach. The authors examined prospectively the relationship between smoking and these cancers in an endemic region.


METHODS
The data used were a cohort study on the relationship between lifestyle and health in the region having the highest liver cancer mortality in Japan. Of the cohort members, 4050 males aged > or =40 years were included in the present analysis with a 9-year mean follow-up. Cox proportional hazards regression was used to estimate relative risks (RR) for cancer of the liver, stomach, smoking-related sites and others, while adjusting for age, residence, and alcohol intake.


RESULTS
By the end of the study period, 59 cases of liver cancer and 53 cases of stomach cancer were identified. Current smokers, compared to subjects who had never smoked, had a threefold risk of liver cancer (RR = 3.3; 95% CI: 1.2-9.5) and a twofold risk of stomach cancer (RR = 2.2; 95% CI: 0.8-5.7). Sub-cohort analysis showed that adjustment for history of chronic liver disease did not attenuate the risk of liver cancer. Light/medium smokers had almost the same risk of these cancers as heavy smokers, while they showed a relatively low risk of smoke-related cancers.


CONCLUSIONS
The present results indicate that smoking is a risk factor of liver and stomach cancer in a population with a high background risk for these cancers. However, causal inferences should be made cautiously due to a lack of information on known risk factors.
Mizoue
T
T
Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Kitakyushu, Japan. mizoue@uoeh-u.ac.jp
Tokui
N
N
Nishisaka
K
K
Nishisaka
S
S
Ogimoto
I
I
Ikeda
M
M
Yoshimura
T
T
D000328:Adult; D000368:Aged; D019353:Endemic Diseases / Q000706:statistics & numerical data; D006801:Humans; D015994:Incidence; D007564:Japan / Q000453:epidemiology; D008019:Life Style; D008113:Liver Neoplasms / Q000453:epidemiology* / Q000209:etiology; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects* / Q000453:epidemiology; D013274:Stomach Neoplasms / Q000453:epidemiology* / Q000209:etiology; D015996:Survival Rate