HELICOBACTER-PYLORI INFECTION - GENETIC AND ENVIRONMENTAL-INFLUENCES

Objective: To investigate the importance of genetic effects for acquir ing Helicobacter pylori infection. Design: Cross-sectional study on mo nozygotic and dizygotic twins, reared apart and reared together. Setti ng: Twins from a subregistry of the Swedish Twin Registry, which inclu des entries for about 25 000 twin pairs who were born in Sweden. Measu rements: Helicobacter pylori status was assessed as the presence of an ti-H pylori IgG in 269 pairs of twins, including 36 monozygotic twin p airs reared apart, 64 monozygotic twin pairs reared together, 88 dizyg otic twin pairs reared apart, and 81 dizygotic twin pairs reared toget her. Results: The probandwise concordance rate for H. pylori infection was higher in monozygotic twin pairs (81%) than in dizygotic twin pai rs (63%) (P = 0.001). Probandwise concordance rates for H. pylori infe ction among 124 pairs of twins reared apart were 82% and 66% for monoz ygotic and dizygotic twins, respectively (P = 0.003). The correlation coefficient was 0.66 for monozygotic twins reared apart, and it provid es the best single estimate of the relative importance of genetic effe cts (heritability) for variation in the acquisition of H. pylori infec tion. The heritability estimate from model-fitting analyses was 0.57, a similar result. The remaining variance was accounted for by shared r earing environmental (20%) and nonshared environmental factors (23%). The latter contribute to differences, not similarities, among family m embers. Conclusion: This twin study showed that genetic effects influe nce the acquisition of H. pylori infection because of greater similari ties within the monozygotic twin pairs. Further, sharing the same rear ing environment also contributes to the familiar tendency for acquirin g H. pylori infection.