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.

Dichlorodiphenyltrichloroethane serum levels and breast cancer risk: a case-control study from Mexico.

Some, but not all, epidemiological studies have suggested that dichlorodiphenyltrichloroethane (DDT) may play a role in the development of breast cancer. These investigations have been conducted in countries where this substance has been banned for at least 20 years. We conducted a study in Mexico, a country in which DDT is still being used to control malaria. In a hospital-based case-control study, we compared 141 histologically confirmed cases of breast cancer with 141 age-matched controls (+/-3 years). All subjects were identified at three referral hospitals of Mexico City between March 1994 and April 1996. Reproductive histories and other variables were obtained by structured interviews, DDT/DDE levels were determined in serum by gas-liquid chromatography. The arithmetic mean of serum DDE in lipid basis was 562.48 +/- 676.18 ppb (range, 10.24-4661.44) for the cases and 505.46 +/- 567.22 ppb (range, 0.004 to 4361.75) for the controls, but this difference was not statistically significant. The age-adjusted odds ratios for breast cancer regarding the serum level of DDE were 0.69 (95% confidence interval, 0.38-1.24) and 0.97 (confidence interval, 0.55-1.70) for the contrasts between tertile 1 (lowest level) and tertiles 2 and 3, respectively. These estimates were unaffected by adjustment for body mass, accumulated time of breast-feeding and menopause, and other breast cancer risk factors. These results do not lend support to the hypothesis that DDT is causally related to breast cancer at the body-burden levels found in our study population but do not exclude the possibility that higher levels of exposure could still play a role in the etiology of this tumor.

Prevalence and determinants of lead intoxication in Mexican children of low socioeconomic status.

This paper reports on the prevalence of lead poisoning in children between 1 and 5 years of age living in a marginal area to the north of Mexico City and also includes an evaluation of sources of exposure to this metal in the same area. The results show that 67.5% of the children studied have blood lead (PbB) levels > or = 10 micrograms/100 ml. Twenty-one percent of these children (1987) had PbB levels that required medical evaluation (> or = 20 micrograms/100 ml- < or = 40 micrograms/100 ml), and 112 children needed medical treatment (PbB > or = 40 micrograms/100 ml). In addition, the study found that the probability of higher blood lead levels (> or = 20 micrograms/dl) corresponds to children whose mothers use lead-glazed pottery dishes (OR = 2.80; CI 95%, 1.55-5.07) and to children who habitually bite colored pencils (OR = 2.05; CI 95%, 1.13-3.71) compared, respectively, with children whose mothers do not use that type of dishes and children who do not bite pencils. Our results provide baseline information for estimating the impact and costs of population-based interventions aimed at these populations and also confirm the need to strengthen health education programs to promote the reduction of lead exposure in the general population.

Is DDT use a public health problem in Mexico?

We review the potential impact of DDT on public health in Mexico. DDT production and consumption patterns in Mexico during the last 20 years are described and compared with those in the United States. In spite of the restrictions on DDT use in antimalaria campaigns in Mexico, use of DDT is still higher than in other Latin American countries. We analyzed information from published studies to determine accumulated levels of this insecticide in blood, adipose tissue, and breast milk samples from Mexican women. Current lipid-adjusted DDE levels from women living in Mexico City are 6.66 ppb in mammary adipose tissue and 0.594 ppm in total breast milk. Finally, the methodological limitations of existing epidemiological studies on DDT exposure and breast cancer are discussed. We conclude that DDT use in Mexico is a public health problem, and suggest two solutions: identification of alternatives for the control of malaria and educational intervention to reduce DDT exposure. We also recommend strengthening epidemiological studies to evaluate the association between accumulated DDT levels in adipose tissue and breast cancer incidence among Mexican women.

Histological types of gastric cancer in Mexico.

BACKGROUND: Gastric cancer is the second leading cause of malignant tumours in Mexico. The distribution of the histological types of this tumour has not been estimated from a population-based representative sample. METHODS: The histological types of gastric cancer according to the Lauren classification and selected socio-demographic characteristics for 220 patients from different socioeconomic levels are reported. The study population represents 66% of all new gastric cancer cases during 1989-1990 reported to the Mexico City Cancer Registry. The patients attended four public hospitals, seven social security hospitals and four private hospitals in Mexico City. A second histological diagnosis was performed by one pathologist. RESULTS: No specific histological type of gastric cancer predominated since the estimated distribution for intestinal gastric cancer was 44.5%, for diffuse gastric cancer 43.2% (and the remaining 12.3% corresponded to indeterminate tumours). The distribution of intestinal and diffuse gastric cancer did not vary significantly according to socioeconomic level or medical care unit and it showed a clear relationship with gender, the intestinal type of gastric cancer being more common among males. CONCLUSIONS: Mexico may not have been affected by the gastric cancer epidemic at the beginning of the twentieth century but the available information and the results of this study are only useful to demonstrate that, currently, no histological type of gastric cancer (according to Lauren's classification) predominates significantly in this country.

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.

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.

Lactation and lead body burden turnover: a pilot study in Mexico.

A pilot study was conducted in Morelos, Mexico in March 1999 to assess the body burden of lead in 24 Mexican women of childbearing age. Lead levels were measured in whole blood and at three bone sites: two primarily trabecular (calcaneus and patella) and one primarily cortical (tibia). Demographic and reproductive characteristics of the women and potential sources of lead exposure were gathered by a direct interview. An inverse relationship was noted between months of lactation and age-adjusted calcaneus lead level (P = 0.001). No association was observed between age-adjusted patella or tibia lead level and months of lactation (P = 0.15). Blood lead levels were positively associated with the use of lead-glazed ceramics (P = 0.01). Bone and blood lead levels were observed to be 77% higher in these rural Mexican women than in urban New York City women. This pilot study provides further limited evidence for the hypothesis that lead mobilization occurs during lactation.

Age of natural menopause among women in Mexico City.

OBJECTIVES: The average age of menopause among women in Mexico City was calculated, considering their reproductive and socio-demographic characteristics. The information was obtained from a population-based control group from a case-controlled study of gynecologic cancer. METHODS: Interviews were carried out with 1005 women resident in Mexico City chosen at random from a sample using the housing sample framework of the Mexico General Directorate of Epidemiology, 472 of whom had undergone a natural menopause. RESULTS: The most important results include an average age for menopause in this population of 46.5 +/- 5 years (95% C.I. 46-48) with a median of 47. Groups of women with an average early menopause were those with no formal education (1.6 years), low socio-economic level (1.3 years, P < 0.05), nulliparas (2.6 years, P < 0.05), those who had never breastfed (2.2 years, P < 0.05) and those who had not used contraceptive hormones (1.7 years, P < 0.05). CONCLUSION: This phenomenon must be documented in Mexico because of its strong links with the morbidity and mortality of the growing number of women who are reaching advanced ages and whose survival is calculated at 30 years after menopause.

Quality control study on negative gynecological cytology in Mexico.

An external evaluation of the quality of diagnosis of gynecological cytology specimens (Papanicolaou or "Pap" tests) in the Cytopathological Laboratory at the Mexico General Hospital was performed, with evaluation of 6,011 Pap tests randomly selected from 31,378 Pap studies previously reported as negative during 1988-1989. These tests were part of the early detection program for cervical cancer run by the Ministry of Health of Mexico City. A quality index for specimens was constructed based on the presence of endocervical cells, mucus, and squamous metaplastic cells. The index of false negatives for the diagnosis of cervical neoplasm in this sample which correspond to diagnostic error by the examiner was 0.18% (11). The constructed quality index revealed that 64.1% of specimens were low quality. The correlation between diagnostic error and low quality was .87. Results indicate that laboratories participating in early detection programs for cervical cancer in developing countries need to implement (1) external evaluation programs for Pap diagnosis; (2) permanent training programs in registration; and (3) monitoring procedures for collection, fixation, and transportation of cytologic materials.

Validity and reproducibility of cytologic diagnosis in a sample of cervical cancer screening centers in Mexico.

OBJECTIVE: To evaluate the diagnostic precision of the cervical cytology (smear) in a sample of 16 cervical cancer screening centers (CCSCs) from the Mexican Ministry of Health and Mexican Institute for Social Security CCSCs distributed across the country. STUDY DESIGN: Each center received a batch of 90 cytologic specimens with a random positive prevalence of 1.5-36%. Positive cases were always histologically confirmed. The "gold standard" was an expert pathologist certified by the Mexican Board of Pathology. RESULTS: Our results show that cytologic diagnosis validity and reproducibility vary greatly within and between institutions. The false negative rate (FNR) varied between 10% and 54%, independent of the prevalence of positive cases. CONCLUSION: Quality control of diagnostic precision is central to the consistency of results obtained at CCSCs. In Mexico the high FNR calls for governmental regulation of cytopathology policies and methods, such as through national and international accreditation of cytotechnology programs. In order to decrease the FNR, developing countries must frame managerial development strategies to streamline the cervical cancer screening program, including continuing education, improvement of operation processes in CCSCs, internal and external quality control of cytopathology laboratories and cervical sampling procedures, and standardization of diagnostic criteria.

Levels of dichloro-dyphenyl-trichloroethane (DDT) metabolites in maternal milk and their determinant factors.

To document the levels and the determinants of dichloro-dyphenyl-trichloroethane (DDT) metabolites in maternal milk, we conducted a cohort study of 50 adult females who lived in Mexico City. We measured social and dietary characteristics via interview. Levels of DDT metabolites were determined by gas-liquid chromatography. The mean values (lipid milk basis) were 0.162 ppm p,p'-DDT; 0.138 ppm o,p'-DDT; and 0.594 ppm 2,2(bis)p-chlorophyenyl-1-1-dichloroethylene (DDE). The main determinants of DDT metabolites were maternal age, lifetime lactation, history of living in an agricultural area, and consumption of salted meat and fish. We estimated that 6.0% of the breast-fed babies had daily intakes of DDT above the level of 0.005 mg/kg d recommended by the World Health Organization/Food and Agriculture Organization of the United Nations (WHO/FAO). Health-outcomes research among children is needed, and investigators should design or adjust current surveillance programs.

Alcohol consumption and gastric cancer in Mexico.

This paper presents an assessment of alcohol consumption, including the popular Mexican liquor tequila, in relation to the incidence of gastric cancer. We conducted a population-based case-control study in Mexico City, with 220 gastric cancer cases and 752 population-based controls. A food frequency questionnaire was used to measure consumption of alcohol and other dietary items. Grams of ethanol were estimated by the Food Intake Analysis System 3.0 software. After adjustment for known risk factors, wine consumption was positively associated with the risk of developing gastric cancer (OR=2.93; CI 95% 1.27-6.75) in the highest category of wine consumption, corresponding to at least 10 glasses of wine per month, with a significant trend (p=0.005). This association remained among intestinal (OR=2.16; CI 95% 0.68-6.92, p-value for trend=0.031 ) and diffuse (OR=4.48; CI 95% 1.44-13.94, p-value for trend=0.018 ) gastric cancer cases. A borderline significant trend between GC risk and total ethanol intake was observed (p=0.068). Consumption of beer and distilled alcoholic beverages including brandy, rum, and tequila was not associated with GC risk. The results indicate the need to focus on the study of the potential effects of different types of wine, with emphasis on components other than ethanol regarding the incidence of gastric cancer, even among populations with moderate to low levels of alcohol consumption.

[Reproductive risk factors and sexual history associated with cervical cancer in Mexico]. / Factores de riesgo reproductivo e historia de vida sexual asociados a cáncer cervical en México.

Uterine cervical cancer is one of the principal public health problems in Mexico. The national mortality rate for cervical cancer in 1991 is estimated at 9.5 per 100,000 women, representing 4,194 deaths. In the period from August 1990 to December 1992, a case-control study was carried out that included 630 cases of histologically confirmed cervical cancer in eight Mexico City hospitals (two for people with no social security cover, four of the social security system and two private). As controls, 1,005 women were chosen from a random sampling of houses in the Mexico City metropolitan area. The main cervical cancer risk factors found in this study, adjusted for a multivariate model, were multiple normals births (with five births OR of 1.93 and 95% C.I. of 1.22-2.73) and a history of two or more sex partners (the OR with four or more sex partners was 5.56 and a C.I. of 2.3-13.4). In addition, there was an estimated lower risk of disease related to starting a sex life after 25 years of age (OR 0.41 with C.I. of 0.25-0.69) and to having cesareans as compared versus one normal birth (OR 0.28 and C.I. of 0.13-0.61). The information obtained is relevant since it identifies Mexican women with a high-risk of developing cervical cancer which can be used in planning programs for the early detection of cancer in this population.

[Helicobacter pylori infection and gastric cancer in Mexico. A challenge for prevention and population control]. / Infección por Helicobacter pylori y cáncer gástrico en México. Un reto para la prevención y el control poblacional.

The International Agency for Research on Cancer (IARC) of the WHO has recognized a cause-effect relationship between Helicobacter pylori (Hp) infection and gastric cancer of such magnitude that the presence of this infection increases the risk of gastric cancer approximately four times. Gastric cancer is currently the second cause of mortality due to malignant neoplasms in Mexico City. This article explores the association between Hp infection and gastric cancer incidence through an epidemiological study including 109 gastric cancer patients and 177 hospital controls in Mexico City. The study estimates that, in the population studied, Hp infection was present in 87.2% of the cases, compared with 82.5% of the controls. The odds ratio of having gastric cancer if infected with Hp was 1.44 IC95% 0.7-2.8. In addition, it was calculated that with eradication of Hp infection in the general population, gastric cancer incidence would decrease by at least 26.6%. An improvement of the actual sanitary conditions along with the development of an effective vaccine for Hp infection and the existence of increasingly effective treatments to eradicate the bacteria are the necessary next step for populational prevention and control of gastric cancer.

[Dietary fiber and gastro-intestinal tumors, implications for the Mexican population]. / Fibra dietética y tumores gastrointestinales, implicaciones para la población mexicana.

Certain nutrients serve as individual influences in the development or protection against chronic and/or degenerative diseases. Specifically, it has been observed that the abundant consumption of dietetic fiber is a protective factor against tumors of the digestive system. Many scientific articles have reported mechanisms by which dietetic fibers exert an important protective effect for colon cancer and in lesser degree against cancer of the stomach and rectum. In Mexico during 1990, neoplasms were the second cause of general mortality for the persons over the age of 65 years. The Fourth National Report of Cancer in Mexico revealed that tumors of the digestive tube were the third most frequent type of neoplasm in the country and that stomach cancer had the greatest incidence among cancers which affect this system. To date, we do not know how much the urban immigration and the consequent changes in food patterns have acted as cofactors for the increase in this type of tumors. During the seventies, a number of national and regional nutritional surveys showed that the Mexican population had a high consumption of fiber, as part of the traditional diet, comprised primarily of tortilla and beans. At the present time, the national dietary patterns have changed; the increasing consumption of high energy foods with a low nutritional value is associated with much less ingestion of dietary fiber. This article points out that the population may have additional digestive cancer risks, due to new food consumption patterns which have reduced the availability of dietary fiber.

[Consumption of foods prepared with corn, wheat and rice and its relationship to gastric cancer incidence in Mexico]. / El consumo de alimentos preparados con maíz, trigo y arroz, y su relación con la incidencia de cáncer gástrico en México.

To assess the consumption of food prepared with corn, wheat or rice, in relation to the risk of developing gastric cancer (GC). We analyzed information about cereal consumption using data from a study of diet and GC for which 220 histologically confirmed incident GC cases and 752 population-based controls, were recruited. All subjects were interviewed using a food frequency questionnaire in which the consumption of 11 foods prepared with corn, wheat or rice, 54 additional food items and 4 alcoholic beverages was assessed. Adjusting by age, gender and total caloric intake, the results did not show an increased risk for gastric cancer incidence in regard to the consumption of foods prepared with corn (O.R. q4 vs. q1 = 0.97 C.I. 95% 0.58-1.63), wheat (O.R. q4 vs. q1 = 1.07 C.I. 95% 0.62-1.84) or rice (O.R. q4 vs. q1 = 1.36 C.I. 95% 0.96-1.90). These results remained similar after stratifying by histological type of GC (i.e. intestinal vs. diffuse). Our results do not lend support to the hypothesis that the consumption of foods prepared with corn, wheat or rice increase the risk of being diagnosed with gastric cancer.

[Cancer of the uterine cervix. Historical perspective]. / Cáncer de cuello uterino. Una perspectiva histórica.

This paper describes the existing etiological paradigms which explain the development of cervical cancer (CACU), and particular, is a review of the historical attempts to explain the occurrence of the disease. Previous analysis concerning the prevalence of CACU in populations has been based on empirical work which can be summarized in several public health models, including: biomedical, hygienist-preventive, epidemiologic, ecologic, and social medical. We conclude that the existing paradigms must be reoriented in order to formulate organized social responses for the control of CACU.

[Is cancer preventable?]. / Es prevenible el cáncer?

Cancer prevention is possible when the causes and risk factors for this disease are known and can be avoided. Lung, breast, stomach and cervical cancers are those with the highest incidence internationally. Smoking, diet, physical activity and certain viruses are factors that have potential for modification, and they determine most of the cancers in the world. To reduce cancer risk, the following is recommended at the individual level: increasing fruit and vegetable consumption, decreasing consumption of red meats, animal fats and alcoholic beverages, avoiding smoking, exercising regularly and avoiding weight gain. Health education, restrictions as to where smoking is prohibited and establishing taxes on tobacco consumption are the principal strategies for designing population prevention programs.

[Evaluation of a program for the early detection of cancer of the uterine cervix in Mexico City. A populational-based epidemiologic study of cases and controls]. / Evaluación del programa de detección oportuna del cáncer del cuello uterino en la Ciudad de México. Un estudio epidemiológico de casos y controles con base poblacional.

Cervical cancer is still an important public health problem in Mexico; in spite of the development of various programs aimed at lowering mortality due to this disease, impact has not yet been achieved. In this study we present an evaluation of the Early Detection Program for Cervical Cancer in Mexico City. The authors carried out a case-control study with a populational base, in which a sample of cases obtained in eight hospitals and a sample of controls representative of the general population were included. We report a protective effect attributed to the program. The women with complete cytology showed 2.4 times less risk of cervical cancer. Nevertheless the effect of the program at a populational level is still limited because it covers only 20 per cent of the cases in the population. The results indicate the need for developing operative research programs in order to increase the demand for and the quality and efficiency of preventive services.