Special Section Trends in Helicobacter pylori Infection and Gastric Cancer in Mexico Javier Torres, 1 Lizbeth Lopez, 2 Eduardo Lazcano, 2 Margarita Camorlinga, 1 Lourdes Flores, 2 and Onofre Mun ˜ oz 1 1 Infectious Diseases Research Unit, Pediatric Hospital CMN-SXXI, Instituto Mexicano del Seguro Social and 2 Center for Public Health Research, National Institute of Public Health, Cuernavaca, Morelos, Mexico Infection by Helicobacter pylori affects about 50% of the human population. Of those infected, 10% to 15% will develop peptic ulcer and up to 3% will present with gastric cancer. These estimates suggest that around 7% of the world’s population will eventually develop H. pylori – associated gastroduodenal dis- ease. In fact, gastric cancer remains the second cause of cancer mortality worldwide (1). Fortunately, evidence suggests that the prevalence of H. pylori infection is decreasing in developed countries; accordingly, a decrease in peptic ulcer and cancer is also being observed (2). It remains uncertain whether the infection is also decreasing in developing countries. The aim of this review is to present the trend of both H. pylori infection and gastric cancer in Mexico, a country where sanitary and public health conditions have been improving during the last decades. Trends in Gastric Cancer A recent report addresses the issue of gastric cancer trends in Mexico (3). The rate of gastric cancer mortality was f4.5 per 100,000 in 1980 and has increased to 6.5 per 100,000 in 10 years (Fig. 1). The increase was more evident in males, where the rate increased from below 4.0 per 100,000 in 1980 to over 6.5 per 100,000 in 1998. Although a fraction of the increase in cases might be due to improvements in reporting of gastric cancer to the cancer registry, the increase is still important and of concern for health authorities. Thus, in contrast to reports from other countries, in Mexico, gastric cancer rates are not decreasing; on the contrary, trends show it is on the rise. As expected, the mortality rates associated with gastric cancer increase with increasing age (3); thus, it is <1.0 per 100,000 in individuals below the age of 30 years, between 1 and 10 per 100,000 in the 30- to 50-year-old group; around 10 per 100,000 in the 50th to 60th decade and close to 100 per 100,000 in individuals over age 70. The same study (3) documents an increase in mortality rates mainly in the 20- to 40-year-old age group, suggesting that the increase in mortality in the younger age groups is of greatest concern. Trends in H. pylori Infection In 1998 we reported on a national seroprevalence survey that tested over 11,000 serum samples collected in Mexico from 1987 to 1988 for H. pylori infection (4). Samples represented all ages and all regions of the country and included all socioeconomic levels. The study documented a seropositivity of 20% in children as young as 1-year-old, and by the age of 10 years almost 50% of the children were infected (Fig. 2). In adolescents, prevalence of infection increased steadily, and by the age of 20 years, 70% of the populations was infected. These seroprevalence values are similar to reports from other developing countries (5) and further document that the acquisition of H. pylori is more common during childhood. In fact, the calculated increment in seropositivity per year was >6% for children <5 years old; this rate decreased to below 3% in children 10 to 14 years and to <0.5% in individuals 30 to 69 years of age. In individuals older than 70 years, the annual change in seropositivity became negative. Overcrowding, low educational level, and low socioeconomic level were risk factors for infection, as previously reported. Geography had little influence on H. pylori infection; regions with different levels of development had similar rates of infection, and no difference in infection between urban and rural communities was found. Females were slightly but significantly more likely to be infected than were males. We recently reported a study where over 5,000 adolescents from the central part of Mexico were tested for H. pylori infection (6). Samples were collected during 1999 to 2000 and included individuals from 11 to 24 years of age. The H. pylori seropreva- lence was directly related to age in multivariate analyses. The likelihood of infection increased with each year of increase in age (odds ratio, 1.10; 95% confidence interval, 1.08-1.13). Availability of sewerage and availability of home appliances at the time of the subject’s birth were also inversely associated with H. pylori seroprevalence. The associations of infection with region, flooring material, overcrowding, sexual intercourse, and history of use of illicit drugs, alcohol, and tobacco were not significant after adjusting for other potential confounders. Seroprevalence found in this study was compared with that of the national seroprevalence survey conducted during 1987 to 1988 (Fig. 3). It should be noted that the trend of increasing prevalence with age was similar in both studies, although the seroprevalence was in general lower in the Morelos study. A difference of almost 15% was observed in children 11 to 14 years of age and 10% in adolescents; the gap decreased to <10% in young adults. The same ELISA in the same laboratory was used in both studies; thus, the observed differences are not likely to be due to the assay methodology. A possible explanation is that in the sample used in this study (1999-2000), the rate of infection had decreased as compared with the 1987 to 1988 sample of the National Survey. The greatest decrease would correspond to the preadolescent group (see Fig. 3), suggesting that socioeconomic status and development have improved in the last few years in our country. Distribution of Gastric Cancer Mortality Rates and H. pylori Seroprevalence in the Country We analyzed the distribution of H. pylori seroprevalence found in the 1987 to 1988 national survey and the mortality 1874 Cancer Epidemiol Biomarkers Prev 2005;14(8). August 2005 Cancer Epidemiol Biomarkers Prev 2005;14(8):1874 – 7 Received 2/11/05; revised 4/16/05; accepted 4/29/05. Grant support: CONACYT, Mexico and Coordinacion de Investigacion en Salud, IMSS, Mexico. Requests for reprints: Javier Torres, Unidad de Investigacion en Enfermedades Infecciosas, Av. Centenario 1707-39, Col. Bosques de Tarango, Me ´xico D.F., C.P. 01580. Phone: 011-52-5-761-0918. E-mail: jtorresl@axtel.net Copyright D 2005 American Association for Cancer Research. doi:10.1158/1055-9965.EPI-05-0113 Downloaded from http://aacrjournals.org/cebp/article-pdf/14/8/1874/2264246/1874-1877.pdf by guest on 01 July 2022