Cancer Research Lab

Family size and birth order significantly influence the risk of Helicobacter pylori infection, which is associated with the development of gastric cancer, according to a report in the January PLoS Medicine.

“This work provides evidence that early life environmental considerations, as reflected by family structure, affect the risk of cancer 6 to 7 decades later, quite late in life,” Dr. Martin J. Blaser from New York University School of Medicine, New York said. “This is the striking observation.”

Dr. Blaser and colleagues investigated the association of early-life family structure and H. pylori cagA status with the risk of developing gastric cancer decades later in 261 Japanese-American men who developed gastric cancer over a 28-year observation period and 261 matched controls.

Men who developed gastric cancer were 2.97 times as likely as men who didn’t develop cancer to have H. pylori infection and 1.8 times as likely to have cagA-positive strains of H. pylori, the authors report.

Although there was no significant association of family size or birth order with gastric cancer risk overall, the results indicate, H. pylori-positive men who were born in the largest sibships were significantly more likely to develop gastric cancer than men in smaller sibships.

Men from the largest sibships who also carried cagA-positive H. pylori were at the greatest risk of developing gastric cancer, the researchers note.

In H. pylori-positive men, higher (later) birth order increased the risk of developing intestinal but not diffuse-type gastric cancer, the report indicates. The same was true for men with cagA-positive strains.

“The results imply that individuals who belong to high-risk populations–East Asians, Eastern Europeans, and Latin Americans who are late-born siblings in large sibship–should be screened particularly carefully, because they are at highest risk,” Dr. Blaser said.

We think of H. pylori as the indicator organism for a potentially large group of indigenous microbes that gradually are disappearing from human ecosystems,” Dr. Blaser explained. “As is the case for H. pylori, these changes may have important implications for health and disease.”