Discussion
Our large epidemiological study of the distribution of H pylori prevaleace among families used a different approuch from that used in other studies addressing the same topic. It was designed as a population study, and all the consenting residents of a small town were involved, thus avoiding the biases that previous studies on selected series could have had. We studied all the consenting families in one community, representing a valuable sample (66%) of the entire population. Infection of children could be related directly to parents' positivity and family's social background.
The overall prevalence of H pylori infection differed according to age, and within children aged 12~16 years the prevalence of infection was similar to that found in a population based study performed in San Marino, an area not far from Campogalliano, but different from other reported values. The prevalence of H pylori infection in children was, for example, 40% in Saudi Arabia, 60% in India, and only 10%~15% in the United States. This is probably related both to the different age groups considered (5~10 years. 3~10 ycars. and 3~5 years, in the thrce countries). and to the different conditions that the children live in.
In our study the prevalence of H pylori infection in children was higher if the social conditions were lower. H pylori prevalence was significantly higher (P<0.005) among children of farmers than among children of blue and white collar families. Moreover, children living in white collar families had a lower risk of being positive for H pylori. Their findings confirm the results of a study by Malaty and Graham which showed a strong inverse correlation between childhood social class and H pylori infection. However, we found no correlation between occupancy rates and H pylori infection, and this is consistent with the fact that the hygiene conditions of families belonging to the same community should be similar.
Finally, we found that children living in families in which both parents were infected had a significantly higher rate of infection than children with only one oг no parents infected. These findings suggest close personal contact of family members living in the samc houscholds and support and oro-oral or faecal-oral route of transmission for H pylori, as shown by other authors.
Although the prevalence of H pylori infection in children with two positive parents was Iower than that reported by Drumm et al (probably because they studied a selected series), it was similar to that found in two other studies. Malaty et al studied family clustering of H pylori infections in families of healthy asymptomatic volunteers and showed that H pylori infection was higher among children with a positive parent (Mother or father) than among those whose parents were negative (50% v 5% respectively). Offspring of infected index cases were more likely to be infected than those of uninfected index cases, regardless of whether the infected case was the mother or father. The second study evaluated mothers, fathers. and siblings of index children separately and concluded that mothers of H pylori infected children were more likely to be positive.
The strong association between infection in mothers and their children may be explained by a greater chance of person to person contact between them within a family. We also found that the prevalence of H pylori infection among children was higher when the mother, rather than the father, was infected (33%vs.25%).
In conclusion, our findings confirm, in an open population, a relation between H pylori infection in children and parents and that social environment has a role in spreading the infection. Although the association between parental and children's infection supports the hypothesis of a person to person, probably oro-oral, transmission of infection, the effect of social environment raises the need for further research to assess whether aspects of lifestyle (housing, dietary habits. etc.) could have a role.
[BMJ. 1999:319: 537-41]
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