Rare Helicobacter pylori Infection May Explain Low Stomach Cancer Incidence: Ecological Observations in Bali, Indonesia

The incidence rate of stomach cancer in Bali, Indonesia, is estimated to be strikingly lower than that in Japan. We conducted an on-site ecological study to investigate the association between the stomach cancer incidence and Helicobacter pylori (H. pylori) infection. Recruiting 291 healthy persons (136 men and 155 women) from the general population in Bali, Indonesia, we conducted a urea breath test (UBT) to examine H. pylori infection, along with a pepsinogen test to detect chronic atrophic gastritis and urine analysis to estimate sodium and potassium excretion. UBT positivities were 9% (2-15, 95% confidence interval) for men and 7% (1-12) for women, and positive cases for H. pylori IgG antibodies were 1% (0-3) for men and 3% (0-5) for women, significantly lower than the respective values in Japan. Positive pepsinogen tests in Bali were 0% (0-0) for men and 1% (0-4) for women, also significantly lower than the Japanese figures. Computed values for daily salt excretion were $13.3{\pm}4.1g$ (mean${\pm}$SD) for men and $11.1{\pm}3.1g$ for women, as high as corresponding Japanese consumption values. Moreover, the estimated potassium excretion was $3.2{\pm}0.7g$ for men and $2.8{\pm}0.6g$ for women in Bali, significantly higher than the figures in Japan. There were no associations across genetic polymorphisms of IL-beta, TNF-alpha, and PTPN11 with UBT positivity. The low incidence of stomach cancer in Bali may thus mainly be due to the rare H. pylori infection. Namely, the bacterium infection seems to be a critical factor for gastric cancer rather than host or other environmental factors.