Prospective study of educational background and stomach cancer in Japan.

BACKGROUND

Different lifestyle choices are commonly regarded as a reflection of socioeconomic status, and the latter is inversely correlated with the risk of developing stomach cancer. However, the details of this association are still unclear in terms of the degree to which lifestyle factors are having impact. To explain the correlation between socioeconomic status and stomach cancer, we therefore examined the roles played by different lifestyle factors.

METHODS

A prospective cohort study of diet and cancer was initiated in Japan during 1988. Data were collected by means of a self-administered questionnaire. A follow-up survey was conducted annually, and the cause of death was recorded from the death certificate. The total of 127,477 study participants resided in 45 areas of Japan, and we retrieved data for 18,746 men and 26,184 women for the present analysis. After 328,030 person-years of follow-up, 379 deaths from stomach cancer were detected: 261 in men and 118 in women.

RESULTS

For men, the age-adjusted relative risk was lowest in the highly educated group (relative risk = 0.72, 95% CI: 0.50-1.04). Relative risk after adjustment for age and dietary choices (including pickles, vegetables, fruit, green tea, and preference for salty foods) was the same as the age-adjusted relative risk (relative risk = 0.72, 95% CI: 0.50-1.04).

CONCLUSION

The expected inverse correlation between education level and death from stomach cancer was observed in men. However, this association could not be explained by differences in dietary habits, smoking, or alcohol consumption associated with socioeconomic status.