Prenatal dichlorodiphenyldichloroethylene (DDE) exposure and neurodevelopment: a follow-up from 12 to 30 months of age

In order to evaluate the persistency of the association between DDE and infant neurodevelopment we assessed mental and psychomotor development between 12 and 30 months of age in an ongoing cohort in Mexico. A total of 270 singleton children without perinatal asphyxia diagnosis, with a birth weight > or =2 kg, mothers>15 years of age with organochlorine maternal serum levels measured at least in one trimester of pregnancy, and who were evaluated at least in two of the four visits at 12, 18, 24 and 30 months of age, were included in this report. The Spanish version of Bayley Scales of Infant Development II (BSID_II; Bayley, 1993) was administered to the children and Psychomotor Development Index (PDI) and Mental Development Index (MDI) were calculated. Information about stimulation at home was measured using the Home Observation of Measurement of the Environment (HOME) at 6 months, and breastfeeding history was obtained through direct interviews with the mothers. Maternal serum DDE levels were determined during pregnancy by means of electron capture gas-liquid chromatography. The association between DDE prenatal exposure and neurodevelopment was estimated using separate generalized mixed effects models. Our results suggest that the association between prenatal DDE and infant neurodevelopment does not persist beyond 12 months of age even after adjusting for known risk factors for neurodevelopment. In addition, we observed an interaction between early home stimulation and mental improvement at 24 and 30 months of age (p<0.001). The association of DDE with infant neurodevelopment seems to be reversible. However, we cannot rule out that other DDT metabolites may play a role in neurodevelopment.

Dietary intake of polyphenols, nitrate and nitrite and gastric cancer risk in Mexico City

N-nitroso compounds (NOC) are potent animal carcinogens and potential human carcinogens. The primary source of exposure for most individuals may be endogenous formation, a process that can be inhibited by dietary polyphenols. To estimate the risk of gastric cancer (GC) in relation to the individual and combined consumption of polyphenols and NOC precursors (nitrate and nitrite), a population-based case-control study was carried out in Mexico City from 2004 to 2005 including 257 histologically confirmed GC cases and 478 controls. Intake of polyphenols, nitrate and nitrite were estimated using a food frequency questionnaire. High intakes of cinnamic acids, secoisolariciresinol and coumestrol were associated with an approximately 50% reduction in GC risk. A high intake of total nitrite as well as nitrate and nitrite from animal sources doubled the GC risk. Odds ratios around 2-fold were observed among individuals with both low intake of cinnamic acids, secoisolariciresinol or coumestrol and high intake of animal-derived nitrate or nitrite, compared to high intake of the polyphenols and low animal nitrate or nitrite intake, respectively. Results were similar for both the intestinal and diffuse types of GC. Our results show, for the first time, a protective effect for GC because of higher intake of cinnamic acids, secoisolariciresinol and coumestrol, and suggest that these polyphenols reduce GC risk through inhibition of endogenous nitrosation. The main sources of these polyphenols were pears, mangos and beans for cinnamic acids; beans, carrots and squash for secoisolariciresinol and legumes for coumestrol.

Dietary folate and vitamin B12 intake before diagnosis decreases gastric cancer mortality risk among susceptible MTHFR 677TT carriers

OBJECTIVE

To assess gastric cancer survival in relation to dietary intake of methyl donors and the methylenetetrahydrofolate reductase 677C>T (MTHFR 677C>T) polymorphism.

METHODS

A prospective cohort of 257 incidental, histologically confirmed gastric cancer cases was assembled in January 2004 and followed until June 2006. Patients were recruited from the main oncology and/or gastroenterology units in Mexico City and were queried regarding their sociodemographic information, clinical history, and dietary habits 3 y before the onset of their symptoms. The intake of methyl donors was estimated with a food-frequency questionnaire and the MTHFR 677C>T polymorphisms were determined by polymerase chain reaction/restriction fragment length polymorphism analysis. Cox's multivariate regression models were used to estimate the mortality risk of gastric cancer.

RESULTS

MTHFR 677TT carriers with low folate and vitamin B12 intakes had the lowest survival rate in cases of gastric cancer. High intakes of folate and vitamin B12 before diagnosis was associated with decreased gastric cancer mortality risk in susceptible MTHFR 677TT carriers (mortality risk for folate 0.14, 95% confidence interval 0.04-0.46, P for trend=0.001; mortality risk for vitamin B12 0.23, 95% confidence interval 0.08-0.66, P for trend=0.008).

CONCLUSION

Folate and related B vitamins may be used as an intervention strategy to improve the survival outcome of gastric cancer.

Maternal MTHFR 677C>T genotype and dietary intake of folate and vitamin B(12): their impact on child neurodevelopment

Using the Bayley test, the mental and psychomotor development in a cohort of 253 children were evaluated. Maternal dietary intake of vitamin B(12) and folate was assessed from a semiquantitative questionnaire administered during the first trimester of pregnancy. Maternal genotypes of MTHFR (677C>T and 1298A>C), were ascertained by PCR-RFLP. The 677T and 1298C variant alleles were present in 59% and 10% of participants, respectively. A dietary deficiency of vitamin B(12) was negatively associated with mental development (beta = -1.6; 95% CI = -2.8 to -0.3). In contrast, dietary intake of folate (< 400 mg/day) reduced the mental development index only among children of mothers who were carriers of the TT genotype (beta = -1.8; 95% CI = -3.6 to -0.04; P for interaction = 0.07). Vitamin B(12) and folate supplementation during pregnancy could have a favorable impact on the mental development of children during their first year of life, mainly in populations that are genetically susceptible.

Maternal MTHFR polymorphisms and risk of spontaneous abortion

OBJECTIVE

To asses the association between intake of folate and B vitamins and the incidence of spontaneous abortion (SA) according to the maternal methylenetetrahydrofolate reductase (MTHFR) polymorphisms (677 C>T and 1298 A>C).

MATERIAL AND METHODS

We conducted a nested case-control study within a perinatal cohort of women recruited in the state of Morelos, Mexico. Twenty-three women with SA were compared to 74 women whose pregnancy survived beyond week 20th. Intake of folate and B vitamins respectively, was estimated using a validated food frequency questionnaire. Maternal MTHFR polymorphisms were determined by PCR-RFLP and serum homocysteine levels by HPLC.

RESULTS

Carriers of MTHFR 677TT and 1298AC genotypes respectively showed an increased risk of SA (OR 677TT vs. CC/CT=5.0; 95% CI: 1.2, 20.9 and OR 1298 AC vs. AA=5.5; 95% CI: 1.1, 26.6).

CONCLUSIONS

Our results support the role of MTHFR polymorphisms as a risk factor for SA, regardless of dietary intake of B vitamins.

Dichlorodiphenyldichloroethylene exposure during the first trimester of pregnancy alters the anal position in male infants

Anogenital distance (AGD) at birth is regarded as a useful measurement that reflects the prenatal androgenic status in rodents. However, the impact of xenoantiandrogens on human development is largely unknown. The aim of this study was to evaluate the potential antiandrogenic impact of prenatal DDT metabolites (p,p'-DDE and p,p'-DDT) exposure on infant AGD, using a non-age-dependent anal position index (API). As part of an ongoing perinatal cohort study on the effects of organochlorine pesticides in children's neurodevelopment, we conducted a cross-sectional study in 71 infants (37 males and 34 females). Maternal serum levels of DDT metabolites (p,p'-DDE and p,p'-DDT) before and during each trimester of pregnancy were determined by electron capture gas-liquid chromatography. During postnatal home visits at 3, 6, and 12 or 18 months of age, the children's weight and API were evaluated. Multiple lineal regression models were used to estimate the potential endocrine disruptor activity of prenatal p,p'-DDE exposure. Boys had significantly higher API values than girls (0.6 versus 0.5; P < 0.001). Only among boys, a doubling increase of maternal p,p'-DDE serum levels during the first trimester of pregnancy, were associated with a significant reduction of API (beta=-0.02; P= 0.02). No effect of p,p'-DDT on AGD was observed. Evidence of the effect of prenatal p,p'-DDE on external genital differentiation is scarce and not consistent in the literature. Further studies are needed to confirm a hormonal disruptive effect on the development of external genitalia, due not only to p,p'-DDE but also due to other antiandrogenic persistent compounds.

Physiologically based pharmacokinetic modeling of persistent organic pollutants for lifetime exposure assessment: a new tool in breast cancer epidemiologic studies

BACKGROUND

Despite experimental evidence, most epidemiologic studies to date have not supported an association between exposure to persistent organic pollutants (POP) and breast cancer incidence in humans. This may be attributable to difficulties in estimating blood/tissue POP concentration at critical time periods of carcinogenesis.

OBJECTIVES

In this work we aimed to develop a tool to estimate lifetime POP blood/tissue exposure and levels during any hypothesized time window of susceptibility in breast cancer development.

METHODS

We developed a physiologically based pharmacokinetic (PBPK) model that can account for any given physiologic lifetime history. Using data on pregnancies, height, weight, and age, the model estimates the values of physiologic parameters (e.g., organ volume, composition, and blood flow) throughout a woman's entire life. We assessed the lifetime toxicokinetic profile (LTP) for various exposure scenarios and physiologic factors (i.e., breast-feeding, growth, pregnancy, lactation, and weight changes).

RESULTS

Simulations for three POPs [hexachlorobenzene, polychlorinated biphenyl (PCB)-153, PCB-180] using different lifetime physiologic profiles showed that the same blood concentration at 55 years of age can be reached despite totally different LTP. Aside from exposure levels, lactation periods and weight profile history were shown to be the factors that had the greatest impact on the LTP.

CONCLUSIONS

This new lifetime PBPK model, which showed the limitations of using a single sample value obtained around the time of diagnosis for lifetime exposure assessment, will enable researchers conducting environmental epidemiology studies to reduce uncertainty linked to past POP exposure estimation and to consider exposure during time windows that are hypothesized to be mechanistically critical in carcinogenesis.

Meta- and pooled analyses of the methylenetetrahydrofolate reductase C677T and A1298C polymorphisms and gastric cancer risk: a huge-GSEC review

Methylenetetrahydrofolate reductase (MTHFR) is a key enzyme in the metabolism of folate, whose role in gastric carcinogenesis is controversial. The authors performed a meta-analysis and individual data pooled analysis of case-control studies that examined the association between C677T and A1298C polymorphisms (the former being associated with low folate serum levels) and gastric cancer (meta-analyses: 16 studies, 2,727 cases and 4,640 controls for C677T and seven studies, 1,223 cases and 2,015 controls for A1298C; pooled analyses: nine studies, 1,540 cases and 2,577 controls for C677T and five studies, 1,146 cases and 1,549 controls for A1298C). An increased risk was found for MTHFR 677 TT in the meta-analysis (odds ratio (OR) = 1.52, 95% confidence interval (CI): 1.31, 1.77) and pooled analysis (OR = 1.49, 95% CI: 1.14, 1.95). No association resulted for MTHFR 1298 CC (meta-OR = 0.94, 95% CI: 0.65, 1.35; pooled OR = 0.90, 95% CI: 0.69, 1.34). Results from the pooled analysis of four studies on C677T stratified according to folate levels showed an increased risk for individuals with low (OR = 2.05, 95% CI: 1.13, 3.72) versus high (OR = 0.95, 95% CI: 0.54, 1.67) folate levels. Overall, these findings support the hypothesis that folate plays a role in gastric carcinogenesis.

Assessing phytochemical intake in a group of Mexican women

OBJECTIVE

Identify the content of selected phytochemicals (PHYs) in Mexican foods and evaluate the reliability of a food frequency questionnaire (FFQ) in assessing PHYs intake among Mexican women.

MATERIAL AND METHODS

Values for PHYs content were obtained from four different data sets. PHYs intake was assessed in 50 women of reproductive age enrolled in a longitudinal cohort study. Values were obtained from a FFQ administered twice, one year apart in order to evaluate its reliability. Selected PHYs included flavonol (FOL), flavones (FES), flavanol (FAL), secoisolariciresinol (SE), matairesinol (MA), lariciresinol (LA), pinoresinol (PI), cynamic acid (CA) and coumestrol (CU).

RESULTS

Daily PHYs intake ranged from 1.3 microg +/- 0.9 for MA to 116.3 +/- 43.8 mg for CA. The adjusted correlation coefficients ranged from 0.17 for FAL to 0.47 for LA. Pinto beans, oranges, hot sauce, broccoli, apples and onions were the main sources of the selected PHYs daily intake.

DISCUSSION

The results of this study contribute to our understanding of the consumption of PHYs in the Mexican diet, and would help evaluate their potential health impact.

Protective effect of yoghurt consumption on Helicobacter pylori seropositivity in a Mexican population

OBJECTIVE

The aim of the study was to determine the relationship between fermented and unfermented dairy product consumption and Helicobacter pylori seropositivity in a Mexican population.

DESIGN

Dietary interviews were conducted as part of a population-based case-control study in 2005. Serum was obtained for each participant to determine H. pylori seropositivity status. Adjusted odds ratios were estimated from multivariate logistic regression models.

SETTING

Mexico City, Mexico.

SUBJECTS

A random sample of 464 healthy adult residents.

RESULTS

The overall seroprevalence of H. pylori in the study sample was 75.4%. In fully adjusted models, compared with those who did not consume yoghurt, there was a protective effect of eating up to one serving per week of yoghurt and more than one serving per week of yoghurt (odds ratio (OR) = 0.57, 95% confidence interval (CI) 0.35-0.94 and OR = 0.45, 95% CI 0.24-0.86, respectively), with a P for trend of 0.01. There were no effects for the consumption of unfermented dairy products (milk and cheese).

CONCLUSIONS

This study suggests that yoghurt consumption may have a protective effect against H. pylori seropositivity. Additional studies are needed to determine whether consumption of yoghurt or other fermented dairy products can prevent or eradicate H. pylori infection.

Efectos a la salud y exposición a p,p'-DDT y p,p'-DDE: el caso de México

Basado en la revisión sistemática de 32 artículos publicados en PubMed-Medline hasta enero del 2006 y utilizando como palabras clave DDT exposure, human, milk y Mexico; este estudio analiza la situación acerca de la exposición en México a difenildicloroetano (DDT) y su principal metabolito p,p,'-DDE, así como, su posible repercusión sobre la salud humana. Aún cuando, el uso del DDT se suspendió en 1999, los estudios evaluados reportan niveles importantes de p,p'-DDE, en muestras biológicas de suero, tejido adiposo y leche materna de poblaciones no ocupacionalmente expuestas. Así mismo, existen evidencias sobre daños a la salud, especialmente relacionados con el área reproductiva masculina, la lactancia materna y más recientemente daños a nivel celular, así como, alteración en el desarrollo psicomotor de niños expuestos in utero. Aún cuando existen muchas lagunas, acerca de otros efectos adversos a la salud relacionados con la exposición a DDT o sus metabolitos, la experiencia lograda hasta ahora, debe ser tomada en cuenta en México y el resto de Latinoamérica, para que considerando el principio precautorio se legisle sobre el DDT y otros contaminantes orgánicos persistente que tienen actividad y características similares al DDT o sus metabolitos.

In utero p,p'-DDE exposure and infant neurodevelopment: a perinatal cohort in Mexico

BACKGROUND

Evidence suggests that p,p'-dichlorodiphenyldichloroethene (DDE) affects neurodevelopment in infants, although a critical exposure window has not yet been identified.

OBJECTIVES

Our goal was to assess the prenatal DDE exposure window and its effect on the psychomotor development index (PDI) and mental development index (MDI) during the first year of life.

METHODS

We recruited 244 children whose pregnancies and deliveries were uncomplicated, and whose mothers were monitored throughout the pregnancy. Participating mothers were not occupationally exposed to DDT (dichlorodiphenyltrichloroethane) but were residents of a zone in Mexico with endemic malaria. We measured serum levels of DDE before pregnancy and during each trimester of the pregnancy. We evaluated PDI and MDI of the Bayley Scales for Infant Development (BSID-II), at 1, 3, 6, and 12 months of age. We adjusted for quality of the home environment and maternal intellectual coefficient (IQ). We used generalized mixed-effects models for statistical analysis.

RESULTS

Third-trimester DDE level (7.8 +/- 2.8 ppb) was significantly higher than the level at baseline, first, and second trimesters, but the differences never exceeded 20%. Only DDE levels during the first trimester of pregnancy were associated with a significant reduction in PDI (every doubled increase of DDE level reduced the PDI 0.5 points). DDE was not associated with MDI.

CONCLUSIONS

A critical window of exposure to DDE in utero may be the first trimester of the pregnancy, and psychomotor development is a target of this compound. Residues of DDT metabolites may present a risk of developmental delay for years after termination of DDT use.

Assessment of lymphocyte subpopulations and cytokine secretion in children exposed to arsenic

Exposure of several human populations to arsenic has been associated with a high incidence of detrimental dermatological and carcinogenic effects. To date, studies examining the immunotoxic effects of arsenic in humans, and specifically in children, are lacking. Therefore, we evaluated several parameters of immunological status in a group of children exposed to arsenic through their drinking water. Peripheral blood mononuclear cells (PBMCs) of 90 children (6 to 10 years old) were collected. Proportions of lymphocyte subpopulations, PBMC mitogenic proliferative response, and urinary arsenic levels were evaluated. Increased urine arsenic levels were associated with a reduced proliferative response to phytohemaglutinin (PHA) stimulation (P=0.005), CD4 subpopulation proportion (P=0.092), CD4/CD8 ratio (P=0.056), and IL-2 secretion levels (P=0.003). Increased arsenic exposure was also associated with an increase in GM-CSF secretion by mononucleated cells (P=0.000). We did not observe changes in CD8, B, or NK cell proportions, nor did we observe changes in the secretion of IL-4, IL-10, or IFN-gamma by PHA-activated PBMCs. These data indicate that arsenic exposure could alter the activation processes of T cells, such that an immunosuppression status that favors opportunistic infections and carcinogenesis is produced together with increased GM-CSF secretion that may be associated with chronic inflammation.

Occupational toluene exposure induces cytochrome P450 2E1 mRNA expression in peripheral lymphocytes

Print workers are exposed to organic solvents, of which the systemic toxicant toluene is a main component. Toluene induces expression of cytochrome P450 2E1 (CYP2E1), an enzyme involved in its own metabolism and that of other protoxicants, including some procarcinogens. Therefore, we investigated the association between toluene exposure and the CYP2E1 response, as assessed by mRNA content in peripheral lymphocytes or the 6-hydroxychlorzoxazone (6OH-CHZ)/chlorzoxazone (CHZ) quotient (known as CHZ metabolic ratio) in plasma, and the role of genotype (5 -flanking region RsaI/PstI polymorphic sites) in 97 male print workers. The geometric mean (GM) of toluene concentration in the air was 52.80 ppm (10-760 ppm); 54% of the study participants were exposed to toluene concentrations that exceeded the maximum permissible exposure level (MPEL). The GM of urinary hippuric acid at the end of a work shift (0.041 g/g creatinine) was elevated relative to that before the shift (0.027 g/g creatinine; p < 0.05). The GM of the CHZ metabolic ratio was 0.33 (0-9.3), with 40% of the subjects having ratios below the GM. However, the average CYP2E1 mRNA level in peripheral lymphocytes was 1.07 (0.30-3.08), and CYP2E1 mRNA levels within subjects correlated with the toluene exposure ratio (environmental toluene concentration:urinary hippuric acid concentration) (p = 0.014). Genotype did not alter the association between the toluene exposure ratio and mRNA content. In summary, with further validation, CYP2E1 mRNA content in peripheral lymphocytes could be a sensitive and noninvasive biomarker for the continuous monitoring of toluene effects in exposed persons.

Assessment of lymphocyte subpopulations and cytokine secretion in children exposed to arsenic

Exposure of several human populations to arsenic has been associated with a high incidence of detrimental dermatological and carcinogenic effects. To date, studies examining the immunotoxic effects of arsenic in humans, and specifically in children, are lacking. Therefore, we evaluated several parameters of immunological status in a group of children exposed to arsenic through their drinking water. Peripheral blood mononuclear cells (PBMCs) of 90 children (6 to 10 years old) were collected. Proportions of lymphocyte subpopulations, PBMC mitogenic proliferative response, and urinary arsenic levels were evaluated. Increased urine arsenic levels were associated with a reduced proliferative response to phytohemaglutinin (PHA) stimulation (P=0.005), CD4 subpopulation proportion (P=0.092), CD4/CD8 ratio (P=0.056), and IL-2 secretion levels (P=0.003). Increased arsenic exposure was also associated with an increase in GM-CSF secretion by mononucleated cells (P=0.000). We did not observe changes in CD8, B, or NK cell proportions, nor did we observe changes in the secretion of IL-4, IL-10, or IFN-gamma by PHA-activated PBMCs. These data indicate that arsenic exposure could alter the activation processes of T cells, such that an immunosuppression status that favors opportunistic infections and carcinogenesis is produced together with increased GM-CSF secretion that may be associated with chronic inflammation.

Dietary and genetic determinants of homocysteine levels among Mexican women of reproductive age

OBJECTIVE

To evaluate the independent and joint effects of dietary folate, vitamin B(12) consumption and methylenetetrahydrofolate reductase (MTHFR) polymorphisms (677C>T and 1298A>C) on the circulating folate and homocysteine (Hcy) levels among Mexican women of reproductive age.

DESIGN

A cross-sectional, population-based study.

SUBJECTS

The first 130 healthy non-pregnant women (aged 16-34 years) who agreed to participate in a reproductive cohort in Morelos, Mexico.

MAIN OUTCOME MEASUREMENTS

Dietary intakes of vitamin B(12) and folate were estimated using a semiquantitative food frequency questionnaire. MTHFR 677C>T and 1298A>C polymorphisms were ascertained using the PCR-based method. Serum levels of Hcy and folate were determined using high-performance liquid chromatography and radioimmunoassay, respectively.

RESULTS

Genotype frequencies for the MTHFR 677C>T polymorphism were 21.5% (CC), 52.3% (CT) and 26.2% (TT) among Mexican women. Of the population, 22% had the MTHFR 1298AC genotype, while no individual carried the 1298CC genotype. We observed an increased level of Hcy among carriers of the 677TT genotype, compared to carriers of the 677CC genotype. The highest level of Hcy was observed among MTHFR 677TT carriers with low B(12) intake (<2.0 microg/day), which resulted with a significant interaction (P=0.01).

CONCLUSION

Vitamin B(12) is an important determinant of Hcy levels in Mexico. Supplementation of folic acid with vitamin B(12) may be preferable when the MTHFR 677T variant allele is prevalent.

Methylenetetrahydrofolate reductase 677C>T polymorphism and gastric cancer susceptibility in Mexico

This study investigated whether methylenetetrahydrofolate reductase MTHFR 677C>T polymorphism modified gastric cancer (GC) risk independently as well as in combination with folate intake and alcohol consumption. A hospital-based case-control study of 201 cases and 427 controls was conducted in three geographical areas of Mexico, between 1994 and 1996. The MTHFR 677T allele frequency was 51.0% in cases compared with 45.3% in controls. After controlling for dietary sources of folate, alcohol intake and other selected variables, a significant increase in GC risk was found among carriers of the 677TT genotype compared with those with the 677CC genotype (odds ratio (OR) 1.62, 95% confidence interval (CI) 1.00-2.59), with a significant trend (P = 0.048). There were no significant interactions between the MTHFR polymorphism and consumption of folate and alcohol. Our results suggest that the high prevalence of MTHFR 677T allele may be a contributor to the high rate of morbidity and mortality in GC in Mexico.

Low lead environmental exposure alters semen quality and sperm chromatin condensation in northern Mexico

We evaluated environmental-lead (Pb) effects on semen quality and sperm chromatin, considering Pb in seminal fluid (PbSF), spermatozoa (PbSpz), and blood (PbB) as exposure biomarkers in urban men (9.3 microg/dL PbB). Several individuals (44%) showed decreases in sperm quality; sperm concentration, motility, morphology and viability associated negatively with PbSpz, whereas semen volume associated negatively with PbSF. Multiple linear regression estimated PbSF and PbSpz thresholds for alterations in semen quality. Forty-eight percent of samples showed high values of nuclear chromatin condensation (NCD) positively associated with PbSF and zinc in spermatozoa (ZnSpz). ZnSpz values were higher than in fertile men. These results suggest that Pb may affect sperm chromatin by altering sperm Zn availability. PbB was not associated with semen quality or NCD, suggesting that Pb in semen compartments assesses better the amount of Pb in the reproductive tract; therefore, these are better biomarkers to evaluate toxicity at low Pb-exposure levels.

CYP1A2 phenotype and genotype in a population from the Carboniferous Region of Coahuila, Mexico

CYP1A2 regulation by polycyclic aromatic hydrocarbons (PAHs) exposure and polymorphism was investigated in 46 male volunteers from the Carboniferous Region in northern Coahuila, Mexico. PAH exposure was estimated by the urinary excretion of 1-hydroxypyrene (1-OHP), whereas the regulatory effects were assessed by the caffeine metabolic ratio (CMR). Genotype was evaluated by determining 5'-flanking region (-2964) and intron I (734) polymorphisms. A statistically significant difference in the urinary 1-OHP geometric means of Barroterán, Cloete and Juárez (2.30, 0.45 and 0.04, respectively) was observed. As for the genotype, the intron I distribution was 0% C/C, 46% C/A and 54% A/A, whereas that of the 5'-flanking region was 26% G/G, 42% G/A and 32% A/A. Both distributions were in agreement with the Hardy-Weinberg equilibrium model. A greater enzyme activity was observed in the A/A compared to C/A individuals according to the CMR (P<0.001), whereas the 5'-flanking region polymorphism showed no effect on CYP1A2 enzymatic activity. These results suggest that intron I polymorphism and PAH exposure are relevant factors that modulate CYP1A2 enzymatic activity.

Genetic polymorphisms and activity of PON1 in a Mexican population

Human paraoxonase (PON1) plays a role in detoxification of organophosphorus (OP) compounds by hydrolyzing the bioactive oxons, and in reducing oxidative low-density lipoproteins, which may protect against atherosclerosis. Some PON1 polymorphisms have been found to be responsible for variations in catalytic activity and expression and have been associated with susceptibility to OP poisoning and vascular diseases. Both situations are of public health relevance in Mexico. Therefore, the aim of this study was to evaluate PON1 phenotype and the frequencies of polymorphisms PON1 -162, -108, 55, and 192 in a Mexican population. The studied population consisted of unrelated individuals (n = 214) of either gender, 18-52 years old. Serum PON1 activity was assayed using phenylacetate and paraoxon as substrates. PON1 variants, -162, 55, and 192, were determined by real-time PCR using the TaqMan System, and PON1 -108 genotype by PCR-RFLP. We found a wide interindividual variability of PON1 activity with a unimodal distribution; the range of enzymatic activity toward phenylacetate was 84.72 to 422.0 U/mL, and 88.37 to 1645.6 U/L toward paraoxon. All four PON1 polymorphisms showed strong linkage disequilibrium (D% >90). PON1 polymorphisms -108, 55, and 192 were independently associated with arylesterase activity; whereas the activity toward paraoxon was related only with PON1 192 polymorphism, suggesting that this polymorphism is determinant to infer PON1 activity. A better understanding of the phenotype and genotypes of PON1 in Mexican populations will facilitate further epidemiological studies involving PON1 variability in OP poisoning and in the development of atherosclerosis.

Is induced abortion a contributing factor to tubal infertility in Mexico? Evidence from a case-control study

OBJECTIVE

To determine the contribution of induced abortion to tubal infertility in Mexico.

DESIGN

Population- and hospital-based case-control study.

SETTING

Tertiary hospitals in Mexico City.

SAMPLE

Women between 20 and 40 years with infertility and controls of the same age: 251 cases, 502 hospital controls, 502 neighbourhood controls.

METHODS

A case-control study was conducted in four tertiary hospitals in Mexico City with 251 cases and 1004 controls (two hospital and two neighbourhood controls per case, matched by age [+/-2 years]). Cases were infertile women, aged 20-40, with tubal occlusion confirmed by laparoscopy. Controls were fertile women, who had carried a pregnancy to term within the last two years. Participants completed a previously validated questionnaire asking about reproductive history and induced abortion.

RESULTS

Our study did not show an association between induced abortion and tubal infertility among women that did not relate both events (cases vs hospital controls: OR = 1.57, 95% CI: 0.29-8.65; cases vs neighbourhood controls: OR = 0.82, 95% CI: 0.07-8.99) using conditional logistic models adjusting by marital status, number of pregnancies, age at first sexual intercourse and history of pelvic inflammatory disease. In contrast, early age at sexual debut and history of pelvic inflammatory disease significantly increased the risk of tubal infertility.

CONCLUSIONS

In Mexico, the lack of association between induced abortion and tubal damage causing infertility observed in this population might be explained by a shift toward "safer" abortion practices.

[Institutional factors contributing to the utilization of breast clinical examination]

OBJECTIVE

To identify factors associated with utilization of breast clinical examination (BCE) and their relationship with institutional medical practice.

MATERIAL AND METHODS

This is a qualitative study conducted between 1996 and 1997 in medical units of Instituto Mexicano del Seguro Social (Mexican Institute of Social Security) and Secretaria de Salud (Ministry of Health). Eight focus groups were included: four groups of female users and four groups of health professionals; in total, 47 users and 29 physicians and nurses participated. Interpretations of information were based on the organizational ability to respond to the user's expectations, "ability/knowledge" within the organization and the institutional medical practice, at the light of the Grounded Theory.

RESULTS

Service demand was conditioned on the perception of poor quality of care, lack of trust in physicians, and organizational aspects. When providing care, male physicians were not interested and felt uneasy about performing the BCE. Female physicians seemed more interested and were well accepted by users.

CONCLUSIONS

Psychological, cultural, social, and institutional barriers exist in the access and utilization of BCE. Identifying these barriers and their origins could support the development of actions to improve the physician-patient relationship. The English version of this paper is available at: http://www.insp.mx/salud/index.html.

Helicobacter pylori-CagA seropositivity and nitrite and ascorbic acid food intake as predictors for Gastric Cancer

A hospital-based case-control study was carried out between 1994 and 1996 to evaluate the risk of gastric cancer (GC) according to Helicobacter pylori-CagA (+) seropositivity, nitrite and ascorbic acid intake. Three geographical areas of Mexico were selected on the basis of their contrasting dietary patterns and H. pylori seroprevalence. Nitrite and ascorbic acid consumption were estimated by interview among 211 cases and 454 matched controls. Serum antibodies against IgG H. pylori and CagA were detected by immunosorbent assays. The adjusted risk for GC was significantly higher among CagA+ subjects compared with those that were CagA negative (Odds Ratio (OR)=2.04 95% Confidence Interval (CI) 1.37-3.02 P for trend P < 0.001), this effect remained significant among diffuse GC cases (OR 2.05 95% CI 1.25-3-36). No significant effects due to nitrite and ascorbic consumption or interactions of these nutrients with CagA seropositivity were detected. Seropositivity to H. pylori CagA+ strains may be an independent factor for diffuse GC in Mexico.

Organophosphorous pesticide exposure alters sperm chromatin structure in Mexican agricultural workers

Our objective was to evaluate alterations in sperm chromatin structure in men occupationally exposed to a mixture of organophosphorus pesticides (OP) because these alterations have been proposed to compromise male fertility and offspring development. Chromatin susceptibility to in situ acid-induced denaturation structure was assessed by the sperm chromatin structure assay (SCSA). Urinary levels of alkylphosphates (DAP) were used to assess exposure. Diethylthiophosphate (DETP) was the most frequent OP metabolite found in urine samples indicating that compounds derived from thiophosphoric acid were mainly used. Chromatin structure was altered in most samples. About 75% of semen samples were classified as having poor fertility potential (>30% of Percentage of DNA Fragmentation Index [DFI%]), whereas individuals without OP occupational exposure showed average DFI% values of 9.9%. Most parameters of conventional semen analysis were within normality except for the presence of immature cells (IGC) in which 82% of the samples were above reference values. There were significant direct associations between urinary DETP concentrations and mean DFI and SD-DFI but marginally (P = 0.079) with DFI%, after adjustment for potential confounders, including IGC. This suggests that OP exposure alters sperm chromatin condensation, which could be reflected in an increased number of cells with greater susceptibility to DNA denaturation. This study showed that human sperm chromatin is a sensitive target to OP exposure and may contribute to adverse reproductive outcomes. Further studies on the relevance of protein phosphorylation as a possible mechanism by which OP alter sperm chromatin are required.

Nutritional factors and breast cancer in Mexico

Breast cancer (BC) morbidity and mortality in Mexico are on the rise, affecting younger women with more frequency. Nutritional factors are often mentioned as determinants of BC but their relevance is not well established in Latin-American countries, where dietary habits show great variation. From a study population previously assembled in Mexico City, 141 histologically confirmed cases of BC were matched by age (+/-3 yr) to an equal number of hospital controls. A food frequency questionnaire was administered to all subjects and the risk of BC was estimated in relation to the intake of selected nutrients. The findings of this study show a protective effect against BC due to a high intake of polyunsaturated fat (odds ratio, OR = 0.10, 95% CI = 0.02-0.40, P for trend = 0.001) and vitamin E (OR = 0.10, 95% CI = 0.02-0.44, P for trend = 0.003) among postmenopausal women. In addition, our findings also suggest that a high intake of total fiber (OR = 0.29, 95% CI = 0.08-1.10, P for trend = 0.080) and carotenes (OR = 0.42, 95% CI = 0.16-1.14, P for trend = 0.088) lowers BC risk among premenopausal women. The relationship between the intake of nutrients and BC risk needs further confirmation.

Dichlorodiphenyldichloroethane burden and breast cancer risk: a meta-analysis of the epidemiologic evidence

The relationship of dichlorodiphenyltrichloroethane (DDT) exposure and breast cancer risk has received increasing attention since the beginning of the 1990s. Contradicting published results regarding the relationship between body burden levels of p,p'-dichlorodiphenyldichloroethane (p,p'-DDE)--the main DDT metabolite--and breast cancer, we argue that such differences stem from methodologic differences among those studies. We performed a meta-analysis of 22 articles using DerSimonian and Laird's method for random effects models. The Q-statistic was used to identify heterogeneity in the outcome variable across studies. The gradient of p,p'-DDE exposure in epidemiologic studies was homogenized to serum lipid bases (nanograms per gram). The potential for publication bias was examined by means of the Begg's test. We discuss methodologic features of the studies in an attempt to reconcile the findings. The summary odds ratio (OR) for selected studies was 0.97 (95% confidence interval, 0.87-1.09) and the gradient of exposure ranged from 84.37 to 12,948 ng/g. No overall heterogeneity in the OR was observed (chi-squared = 27.93; df = 23; p = 0.218). Neither the study design nor the lack of breast-feeding control or the type of biologic specimen used to measure p,p'-DDE levels were the causes of heterogeneity throughout the studies. Evidence for publication bias was not found (p = 0.253). Overall, these results should be regarded as a strong evidence to discard the putative relationship between p,p'-DDE and breast cancer risk. Nevertheless, the exposure to DDT during critical periods of human development--from conception to adolescence--and individual variations in metabolizing enzymes of DDT or its derivatives are still important areas to be researched in regard to breast cancer development in adulthood.

Capsaicin consumption, Helicobacter pylori positivity and gastric cancer in Mexico

Gastric cancer (GC) incidence has not declined in Mexico. We assessed whether the intake of capsaicin (CAP), the pungent compound of chili peppers, increases the risk of GC independently of H. pylori positivity (Hp). From 1994 to 1996, a hospital-based case-control study was performed in 3 areas of Mexico; 234 cases of GC and 468 matched controls were enrolled and their diet and other characteristics were inquired. Chili pepper intake was queried by interview and CAP content of chilies was determined in a separate analysis by gas chromatography to estimate CAP intake; IGg Hp serum antibodies were determined by ELISA. The risk of GC was increased (OR = 1.71; 95% CI = 0.76-3.88) among high-level consumers of CAP (90-250 mg of capsaicin per day, approximately 9-25 jalapeño peppers per day) as compared to low-level consumers (0-29.9 mg of capsaicin per day, approximately 0 to less than 3 jalapeño peppers per day; p for trend p = 0.026); this effect was independent of Hp status and other potential GC determinants and was higher among diffuse GC cases (OR = 3.64; 95% CI = 1.09-12.2; p for trend = 0.002) compared to intestinal GC cases (OR = 1.36; 95% CI = 0.31-5.89; p for trend = 0.493). No significant interaction was found between CAP intake and Hp on GC risk. Chili pepper consumption might be an independent determinant of GC in Mexico.

Dietary and reproductive factors associated with benign breast disease in Mexican women

Benign breast disease (BBD) is common in women in the reproductive age group. The results of epidemiological studies that have examined the relationship between diet and BBD are controversial and scarce. The aim of the present study was to identify and evaluate the impact of dietary and reproductive risk factors in the development of BBD in Mexican women. Between 1994 and 1996, 121 women with BBD and 121 age-matched (+/- 3 yr) clinical controls with non-breast-related diseases were identified. The study population was directly interviewed about their reproductive history, and a semiquantitative food frequency questionnaire was used to obtain dietary information. The population was originally identified as part of a hospital-based case-control study examining exposure to 1,1-bis(p-chlorophenyl)-2,2,2-trichloroethane and breast cancer. A significant reduction in the risk of BBD was observed when comparing the upper with the lower tertiles of consumption of citrus fruit [odds ratio (OR) = 0.43, 95% confidence interval (CI) = 0.21-0.88], non-citrus fruit (OR = 0.35, 95% CI = 0.16-0.76), diary products (OR = 0.36, 95% CI = 0.18-0.75), and food sources of lignans (OR = 0.48, 95% CI = 0.24-0.98). A marginally significant reduction in the risk of BBD associated with the consumption of vitamin B-12 (OR = 0.48, 95% CI = 0.23-1.02) was also observed. Our results add new information about the role of diet in the etiology of BBD.

[Factors associated with quality of life parameters in older adults in Morelos]

OBJECTIVE

This study aimed to identify a set of factors related to quality of life across the dimensions of physical, social and emotional functioning and general health perception in an elderly population from the state of Morelos, Mexico.

MATERIAL AND METHODS

A cross-sectional study was carried out from March to September of 1997 in urban and rural areas of the state of Morelos. The sample was built from randomly selected 2,571 households in the study areas. Data for the study were collected by means of structures personal interviews, using a questionnaire applied to 869 subjects who were 60 years or older at the time of the interview. Quality of life was analyzed in four dimensions: physical, social and emotional functioning and general health perception. Independent variables were: gender, age, perceived morbidity, activity level, health check-up and hospitalization during the last year, tobacco consumption and family income. Statistical analyses went from descriptive statistics to the fitting of multivariate unconditional logistic regression models.

RESULTS

The factors associated with the dimensions of quality of life were: physical functioning; gender, illness in last year, age, tobacco consumption and activity level. In social functioning only health check up was significant, as protector factor of good social quality. In emotional functioning the associated factors were: gender, illness and medical check-up in last year. For the dimension health perception the variables were: gender, illness, hospitalization in last year and activity. All of them statistically significant p < 0.05.

CONCLUSIONS

The factors associated with quality of life vary according to each dimension. However; gender, morbidity, health check up and activity were common for the dimensions studied; so that these aspects should be considered for planning interventions to improve the quality of life in elderly people.

Preterm birth in relation to maternal organochlorine serum levels

PURPOSE

To evaluate the associations of serum levels of p,pacute;-DDE and two other persistent organochlorine pesticides, beta-HCH and HCB, in relation to preterm birth.

METHODS

During 1995 we performed a case-cohort study and 233 mothers were recruited at three large maternity hospitals in Mexico City. Serum levels were obtained shortly after delivery.

RESULTS

A non-significant increased risk of preterm birth in relation to serum p,p'-DDE levels was observed. There was also a suggestion of an increased risk of preterm birth among women in the highest tertile of beta-HCH (adjusted odds ratio 1.85, 95% CI = 0.94-3.66, p value for test of trend p = 0.08) compared with the lowest tertile. No association was found between HCB serum levels and preterm births.

CONCLUSIONS

These findings suggest that p,pacute;-DDE and other organochlorine pesticides may pose a risk to preterm birth in countries that continue to use such insecticides for malaria control.

Serum levels of beta-hexachlorocyclohexane, hexachlorobenzene and polychlorinated biphenyls and breast cancer in Mexican women

Information on the association between exposure to beta-hexachlorocyclohexane (beta-HCH), hexachlorobenzene (HCB) or polychlorinated biphenyls (PCBs) and the incidence of breast cancer is inconclusive. However, exposure to such compounds is a public health concern in Mexico and is subject to recent regulation. Serum levels of beta-HCH, HCB and PCBs were analysed in 95 histologically confirmed breast cancer cases and 95 hospital controls, 20-79 years of age, from Mexico City, enrolled between March 1994 and April 1996. After adjusting for established risk factors, there was no evidence of a relationship between beta-HCH, HCB and PCBs and breast cancer risk (OR for beta-HCH tertile 3 versus tertile 1: 1.05 95% CI 0.46-2.40; OR for HCB tertile 3 versus tertile 1: 0.46 95% CI 0.20-1.07; OR for PCBs 1.31 95% CI 0.33-5.21 for the high category of exposure). This study lends no support to the case for a role for beta-HCH, HCB or PCBs in breast cancer aetiology.

Food consumption and adipose tissue DDT levels in Mexican women

This article analyzes food consumption in relation to levels of DDE (the principal metabolite of DDT) in the adipose tissue of 207 Mexican women residing in States with high and low exposure to DDT. Data on the women's dietary habits and childbearing history were obtained from a personal interview. Adipose tissue DDE levels were measured by gas-liquid chromatography and compared by analysis of variance (ANOVA) and multiple linear regression. Adipose tissue DDE levels increased significantly with age (p = 0.005) and residence in coastal areas (p = 0.002) and non-significantly with the consumption of onion, cauliflower, prickly pear, squash blossoms, sweet corn, broad beans, chili pepper sauce, ham, and fish. Even so, during breastfeeding there was a non-significant reduction in these levels. The findings suggest that certain foods serve as vehicles for DDE residues and confirm that breastfeeding is a mechanism for the elimination of this insecticide, which accumulates over the years in the human body.

Breast-feeding and serum p,p'DDT levels among Mexican women of childbearing age: a pilot study

For almost 50 years, millions of Mexicans have been directly and/or indirectly exposed to (1,1,1-trichloro-2,2-bis[p-chlorophenyl]ethane) (p,p'DDT). The potential related health outcomes of this exposure are of international concern. The objective of the study was to determine the effect of breast-feeding on serum levels of 1,1-dichloro-2; 2'-bis(p-chlorophenyl)ethylene (p,p'DDE) and p,p'DDT in women of childbearing age who were residents of the state of Morelos, Mexico. In March 1999, we examined a sample of 24 women, ages 21 to 36 years, who came with their children to the outpatient facility of a county Health Center in the state of Morelos. The geometric mean for p,p'DDE was 21.8 ng/ml+/-2.58 (GSD) and 2.9 ng/ml+/-2.84 for p,p'DDT. For each month of breast-feeding we observed similar significant decreases for both p,p'DDE (beta=-0.0403 per log concentration unit, P=0.001) and p,p'DDT (beta=-0.0309, P=0.03) serum levels, adjusted by mothers' age and number of children. The adjusted half-life estimate for p,p'DDE serum levels was 17 months. It was concluded that breast-feeding leads to rapid removal of p,p'DDT from the body (<2 year half-life) compared to nonlactational elimination rates (<5 year half-life). In this population, serum p,p'DDE levels were similar to those found 20 years ago in the United States.

Food sources of phytoestrogens and breast cancer risk in Mexican women

We analyzed the intake of selected foods that contain phytoestrogens in relation to breast cancer (BC) risk using data from a hospital-based case-control study performed in Mexico City from 1994 to 1995. A total of 198 women with BC, aged 21-79 years, were individually age matched to an identical number of women with no breast disease. By a direct interview, information on socioeconomic characteristics and diet was obtained. A semiquantitative questionnaire was used to estimate the frequency of consumption of 95 foods. The effect of selected foods that contain phytoestrogens on BC risk was estimated using logistic regression models. The adjusted odds ratio for the consumption of more than one slice of onion per day and BC was 0.27 (95% confidence interval = 0.16-0.47), with a statistically significant trend (p < 0.001). This protective effect remained after adjustment for known risk factors of BC. Among premenopausal women, there was also a protective and significant effect due to the intake of lettuce and spinach and nonsignificant protective effects for the consumption of apples and herbal tea. Additional studies aimed at evaluating the potential protective effect of particular phytoestrogens on BC risk are needed.

Epidemiologic panorama of stomach cancer mortality in Mexico

BACKGROUND

Annually, there are more than 6 million deaths from a type of malignant neoplasia worldwide. In developing countries, the highest rates of incidence of malignant neoplasias are uterine cervical cancer, stomach, lung, esophagus, pharynx, and liver cancers. Recent estimates on the incidence of cancer worldwide show that, in 1990, stomach cancer (SC) was the second most frequent type of cancer (900,000 new cases annually). Rates of incidence have decreased consistently in nearly all areas of the world. In Mexico, however, rates of incidence and mortality have increased gradually between 1980 and 1997; in 1995, 4,685 people died of SC in Mexico. This report presents a descriptive analysis of SC mortality in Mexico.

METHODS

A mortality database edited from the electronic files of the National Institute of Informatics, Statistics and Geography (INEGI) in Mexico was used; population denominators were edited by the Mexican National Population Council (Conapo). Adjusted mortality rates, taking as standard of reference the population of Mexico City by sex, year, and 10-year age groups were calculated as well as the sex ratio for the 1980-1997 period. To evaluate the magnitude of risks by state, the standardized mortality ratio (SMR) was calculated; prematurity was evaluated through the potential lost-life years index (PLLYI). The analysis was carried out using the Excel and Stata 5.0 software programs.

RESULTS

During the years from 1980 to 1997, in Mexico the total number of deaths from SC was 76,315. The male:female ratio was 1.2:1.0. SMR by state showed that the states of Yucatán, Sonora, Zacatecas, Michoacán, and Chiapas had higher mortality rates. The PLLYI was higher for males in the states of Chiapas, Sonora, Chihuahua, Zacatecas, and Southern Baja California, and higher for females in Chiapas, Oaxaca, Yucatán, Puebla, and Campeche.

CONCLUSIONS

World statistics on mortality caused by SC suggest a decreasing trend. Findings for this study show an increase in the adjusted mortality rates by SC during the 1980-1997 period in Mexico. However, when analyzing the different indicators that reveal risks, magnitude, and prematurity of mortality, there is a differential trend in mortality by sex that includes regional patterns probably related to different socioeconomic levels.

[Identification of malignant breast lesions in Mexico]

OBJECTIVE

To evaluate the modes of detection of breast malignancies in Mexico City and to estimate the number of patients diagnosed in advanced stages.

MATERIAL AND METHODS

This cross-sectional study was conducted between 1994 and 1996, among 256 women with a histological diagnosis of breast cancer, at three tertiary level public hospitals in Mexico City. Personal interviews were conducted to collect data on reproductive characteristics, clinical history, and breast cancer modes of detection. Data analysis consisted of percentages, odds ratios, and 95% confidence intervals.

RESULTS

Ninety percent of women sought medical care after identifying a breast lump by themselves. Only 10% of patients had a stage-I tumor; all 27 cases first identified by a physician were in stage II-B and higher.

CONCLUSIONS

An increasing trend of breast cancer mortality in Mexico City will persist, unless a greater proportion of tumors in situ is detected; this would require enhancing breast cancer screening programs and conducting an intense educational intervention among women at risk.

[Lead elimination by traditional curing]

OBJECTIVE

To evaluate traditional acidic curing as a preventive method for reducing lead content of glazed ceramic ware.

MATERIAL AND METHODS

In 27 ceramic ware pieces from four states in Mexico, the level of residual lead was determined through atomic absorption spectrophotometry after four washings with acetic acid 3%.

RESULTS

The lead content of the vinegar washing diminished proportionally with the number of washings, although it remained highly above the permissible levels of this metal (2.5-7.0 p.p.m.).

CONCLUSIONS

Traditional acidic curing of glazed ceramic ware is not a useful preventive measure for reducing lead exposure.

The epidemiology of Her-2/neu and P53 in breast cancer

Breast cancer is an etiologically heterogeneous disease with marked geographical variations. Joint consideration of the relationship between specific molecular alterations and known or suspected epidemiologic risk factors for this disease should help distinguish subgroups of women that are at elevated risk of developing breast cancer. In this article, we present a comprehensive literature review of the etiologic and prognostic roles of Her-2/neu and P53 among women. In addition, we discuss the advantages and limitations of using biomarkers in epidemiological studies. We conclude that more research is needed to understand the complex relationships between genetic alterations and etiologic risk factors for breast cancer.

[Strategies for teaching self-examination of the breast to women in reproductive age]

OBJECTIVE

To develop an effective strategy to inform Mexican women between 12 and 47 years of age about breast cancer (BC) and train them to perform breast self-examination (BSE).

MATERIAL AND METHODS

Between April, 1996 and July, 1998, two different strategies to teach BSE were designed and evaluated in Cuernavaca, State of Morelos, Mexico. These strategies included teaching materials and were based on opinions of women participating in the first stage of this study. Both strategies consisted of the presentation of a leaflet and a video. The first strategy was delivered by a public health nurse in charge of leading the session. The second one was presented by a BC survivor. This second strategy included slides and silicon breast models. These two strategies were then compared to a third one, consisting of a primary care nurse handling out a leaflet and showing a video, based on Health Secretariat's guidelines. In total, 149 women were trained. They were randomly assigned to any one of these three strategies. The effectiveness of the teaching strategies was determined by assessing the changes in the women's knowledge of BC and BSE, as well as in their ability to identify the largest number of lumps on a natural size silicon breast, before and after training. Statistical analysis included Student's t test, variance analysis, McNemar's chi 2, Pearson's chi 2, and multiple linear regression.

RESULTS

With all three strategies, there was an increase of approximately 30% in women's knowledge of BC and BSE as well as in their ability to detect lumps. Although at the beginning of the training only one out of every 20 women were able to identify more than three lumps in the silicon model, by the end between 3 and 4 of every 10 women were able to do this, with values of p < 0.05. Some factors determine women's learning of both BSE and information about BC as well as their ability to identify lumps.

CONCLUSIONS

Teaching BSE with any of the strategies evaluated could be included in an integral program to educate Mexican women on breast cancer prevention and early detection. The appropriate and monthly practice of BSE is linked both to a decrease in the amount of time elapsing between the identification of suspect signs and the demand for medical care, such as requesting a clinical breast examination, which entails identifying small tumors when BC is present.

Nutrient intake and gastric cancer in Mexico

In contrast to the decreasing trends observed in most countries, gastric-cancer mortality has remained at about the same level in Mexico throughout the last 40 years. As part of a study carried out in the metropolitan area of Mexico City, an assessment of nutrient intake and gastric cancer is presented here. The study population comprised 220 cases of gastric cancer and 752 population-based controls. Our results showed 70 to 80% reduction in the risk of developing this tumor, associated with the intake of polyunsaturated fat, fiber and vitamin E; and this effect was independent of the histological type of the tumor (i.e., intestinal or diffuse). On the other hand, an increased risk of gastric cancer was related to the consumption of saturated fat (OR(Q4vs.Q1) = 4.37, 95% CI 1.89-10.12) and, cholesterol (OR(Q4vs.Q1) = 2.39, 95% CI 1.23-4.64), but such effects were restricted to the intestinal type of gastric cancer. In the whole study population, mono-unsaturated fat intake increased the risk for gastric cancer, and a marginally significant increasing trend was observed for protein consumption. The findings from this study add information about the role of specific nutrients in the etiology of gastric cancer.

Nutrient intake and gastric cancer in Mexico

In contrast to the decreasing trends observed in most countries, gastric-cancer mortality has remained at about the same level in Mexico throughout the last 40 years. As part of a study carried out in the metropolitan area of Mexico City, an assessment of nutrient intake and gastric cancer is presented here. The study population comprised 220 cases of gastric cancer and 752 population-based controls. Our results showed 70 to 80% reduction in the risk of developing this tumor, associated with the intake of polyunsaturated fat, fiber and vitamin E; and this effect was independent of the histological type of the tumor (i.e., intestinal or diffuse). On the other hand, an increased risk of gastric cancer was related to the consumption of saturated fat (OR(Q4vs.Q1) = 4.37, 95% CI 1.89-10.12) and, cholesterol (OR(Q4vs.Q1) = 2.39, 95% CI 1.23-4.64), but such effects were restricted to the intestinal type of gastric cancer. In the whole study population, mono-unsaturated fat intake increased the risk for gastric cancer, and a marginally significant increasing trend was observed for protein consumption. The findings from this study add information about the role of specific nutrients in the etiology of gastric cancer.