Intrauterine lead exposure and preterm birth

The objective of this study was to determine the risk of preterm birth in relation to umbilical cord blood lead levels (UCL) among primiparous and multiparous women. A case-cohort study was performed in Mexico City during 1995. A total of 459 full-term births was compared with 161 preterm births (before 37 gestational weeks). Mothers were interviewed before the delivery about their reproductive histories and other related factors of preterm birth. Lead was determined by atomic absorption spectrophotometry. Lead levels were higher in primiparous women who had a preterm birth than in primiparous women with a full-term birth (9.77+/-2.0 microgram/dl vs 8.24+/-2.15 microgram/dl); this difference was marginally significant. After adjusting for other known preterm birth risk factors, the frequency of preterm birth was almost three times higher among women who had UCL levels greater or equal to 5.1 microgram/dl compared to those who had UCL levels lower than 5.1 microgram/dl. This difference was not observed among multiparous women. Our results suggest that intrauterine lead exposure may be associated with preterm birth in first deliveries but not in subsequent ones.

The adipose tissue to serum dichlorodiphenyldichloroethane (DDE) ratio: some methodological considerations

Dichlorodiphenyldichloroethane (DDE) adipose tissue level has been regarded as a preferred indicator of accumulated human exposure to DDT; however, blood sera are more feasible to obtain and analyze than adipose tissue samples. Inconsistent and scarce information exists in relation to the adipose tissue/serum DDE ratio. As a part of a hospital-based case-control study performed in Mexico City from 1994 to 1996, 198 paired serum and adipose tissue samples were obtained from 72 women with histologically confirmed breast cancer and 126 women with benign breast disease. Both adipose tissue and serum DDE levels were determined by gas-liquid chromatography and reported as ppb lipid weight (ng/g) as well as wet basis (ng/ml). Results showed that the adipose tissue/serum DDE ratio (ADSE) varies according to the type of information (lipid vs wet basis, arithmetic vs geometric means) used for its estimation. ADSE gets a value near 1 (1.1) only when the geometric DDE levels in lipid basis are used for its estimation. The correlation between DDE serum and adipose tissue levels was found (r=0.364, P<0.001). The ADSE did not vary by disease status, nor was it altered by parity, history of breast-feeding, and other reproductive characteristics. We endorse the use of venipuncture instead of biopsy as a way to estimate DDT body burden levels in further research.

[Is cancer preventable?]

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.

Dietary factors and the risk of gastric cancer in Mexico City

Dietary factors play an important role in gastric cancer risk but have not been investigated extensively in Mexico. The authors conducted a population-based case-control study of gastric cancer in the Mexico City, Mexico, metropolitan area in 1989-1990. A total of 220 patients with histologically confirmed gastric adenocarcinomas were interviewed. Controls were an age-stratified random sample of residents of the Mexico City metropolitan area. The dietary questionnaire was a 70-item semiquantitative food frequency adapted for the Mexican diet. Odds ratios were calculated for quartiles of consumption of food groups and were adjusted for age, gender, calories, chili pepper intake, cigarette smoking, socioeconomic status, added salt, and history of peptic ulcer disease. There was approximately a threefold increased risk of gastric cancer for frequent consumption (highest quartile) of both fresh meat (odds ratio (OR) = 3.1) and processed meat (OR = 3.2). Odds ratios were also significantly elevated for frequent consumption of dairy products (OR = 2.7) and fish (OR = 2.2). The authors observed a decreasing gradient of risk with increasing frequency of vegetable consumption due to a significant inverse trend for the yellow and orange vegetables. High intake of citrus fruits showed a slight inverse association. Consumption of salty snacks more than twice per month was associated with an 80 percent increased risk, and there was a significant positive trend. These findings are consistent with many studies around the world that indicate important roles for salt, processed meats, and vegetable consumption in gastric cancer risk.

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.

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.

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.

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.

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.

[Reproducibility of a questionnaire for studying climacteric]

OBJECTIVE

This study evaluated the reproducibility of a questionnaire concerned with the clinical and epidemiological aspects of menopause.

MATERIAL AND METHODS

The study population consisted of a hundred perimenopausal Mexican women seeking care at gynecology and obstetric health care services. Their participation was voluntary and they answered the same questionnaire two times with a 15-30 day lag between each application.

RESULTS

The Kappa coefficient was high (0.81-1.0) for categorical variables such as: type of menstrual cycles, type of menopause, breast-feeding, use of estrogen during menopause and use of hormonal contraceptives. The Kappa coefficient was moderate (0.7-0.8) for symptoms related to menopause such as hot flashes, sweating, painful coitus, vaginal dryness and a decrease in libido. Mean differences were calculated for continuous variables such as age at menarche, age at menopause, time using estrogen and the duration of breast-feeding, the majority had a value of zero and 95% confidence intervals for these mean differences included the null value. The questionnaire also included other characteristics such as tobacco consumption and a short food frequency questionnaire, which showed high concordance (Kappa 0.7-1.0).

CONCLUSIONS

The results of this study show that this questionnaire has a high level of reproducibility and can be useful as a research tool to explore menopause in Mexican women.

Exercise and reproductive factors as predictors of bone density among osteoporotic women in Mexico City

We examined the association between physical activity and reproductive factors with bone density among 313 Mexican women, aged 26-83 years. Bone mineral density (BMD) was measured with a HOLOGIC QRD 1000 w, DXA densitometer at the lumbar spine and femoral region. We explored the relation between BMD and parity, age, body mass index (BMI), type of menopause, and level of exercise. Multiple regression models examining determinants of bone density at the lumbar and femoral regions showed that increasing age and lack of exercise were statistically significant predictors of bone demineralization. The number of pregnancies also had a deletereous effect on bone density, especially for lumbar spine, as well as BMI <20 kg/m2. Our results suggest that physical activity, parity, and BMI are important determinants of bone density in this 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.

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.

[Breast cancer. A historical account, present and future]

This essay describes the different theoretical constructions of breast cancer models, such as the biological, hygienist-preventive and epidemiological. An anecdotal account of the Hippocratic model is also presented. This disease will be one of the major challenges posed by noncommunicable diseases in coming years, due to a significant increase of life expectancy and to a decrease of the overall annual growth rate-resulting in the ageing of the population-, as well as to lifestyle changes-particularly the considerable decrease of fertility rates and breastfeeding practices-, and to the poor efficiency and effectiveness of breast cancer screening programs. In this context, one of the main challenges for breast cancer control is to secure the multidisciplinary approach offered by public health. After analyzing the different models, we favor the sociomedical model as the one that incorporates several areas of knowledge to formulate an effective response to breast cancer.

[Reproductive risk factors and sexual history associated with cervical cancer in Mexico]

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.

[Beliefs about chili pepper consumption and health in Mexico City]

Eating chili peppers is a cultural tradition in Mexico. Controversial characteristics have been empirically associated to chili pepper consumption and human health. In this paper, the beliefs about the health impacts of chili pepper consumption in two independent groups of Mexico City residents are described. The results confirm, on the one hand, that there is a wide variety of health benefits and damages associated with chili pepper consumption, but on the other hand, that the levels of chili pepper consumption are not related to beliefs about its human health impact.

[NAFTA: a challenge and an opportunity for environmental health. The case of the maquila industry]

The three countries that have signed the North American Free Trade Agreement (NAFTA) have focused particular interest and concern on the potential impact that this agreement will have on the environmental health, based on the premise that economical development should not detriment neither the environment nor the human health. In this paper, the NAFTA is presented as an opportunity to improve environmental and occupational health in Mexico and assumes that the study of the potential impact of NAFTA could help to find the solutions of the former and actual environmental health problems. From this perspective, the north-border maquila industry is analyzed as a case study for the purpose of identifying and predicting the impact of NAFTA on environmental and the occupational health. Preventive as well as control measurements are suggested. The general characteristics of the U.S.-Mexico border and the maquila industry are presented. The lack of both social investment and urban planning along with population and economical growth are described. An explanation of the impact that these factors have had on the environmental and occupational problems is discussed. Special emphasis is given to the human health problems including that of water, air and soil contamination by industrial toxic residues. Also, some possible health impact of NAFTA are outlined. Finally a sustainable developmental intervention is suggested, based on NAFTA as an opportunity to take advantage of coming structural changes that will improve the environmental health conditions at the northern-border and in the entire country.

[Health risk control for organophosphate pesticides in Mexico: challenges under the Free Trade Treaty]

This paper discusses recent trends concerning the commercialization of pesticides in Mexico and focuses on organophosphates and their potential health risk impact. It points out the existing lack of knowledge on health effects associated to chronic exposure to organophosphate pesticides. A need for both toxicological and epidemiologic studies of chronic exposure is identified. Regulatory programs for pesticides in Mexico and the United States are also compared. The paper also addresses the possibility of effective enforcement of environmental and health regulations in Mexico as a result of more rigorous surveillance under NAFTA.

[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]

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.

[Dietary fiber and gastro-intestinal tumors, implications for the Mexican population]

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.

Chili pepper consumption and gastric cancer in Mexico: a case-control study

Laboratory studies indicate that capsaicin, the hot-tasting component of chili peppers, may be carcinogenic. A population-based case-control study was conducted in Mexico City during 1989-1990 to evaluate the relation between chili pepper consumption and gastric cancer risk. The study included 220 incident cases and 752 controls randomly selected from the general population. Information was collected by interview. Chili pepper consumers were at high risk for gastric cancer compared with nonconsumers (age- and sex-adjusted odds ratio = 5.49, 95% confidence interval (CI) 2.72-11.06). Among consumers, there was a highly significant trend of increasing risk with increasing self-rated level of consumption (low, medium, and high) (p = 2 x 10(-7). The odds ratio for high-level consumers compared with nonconsumers was 17.11 (95% CI 7.78-37.59). However, when consumption was measured as frequency per day, a significant trend among consumers was not observed. Multivariable adjustment increased the magnitude of the chili pepper-gastric cancer association, but a significant trend among consumers (measured as frequency per day) was still not observed. Chili pepper consumption may be a strong risk factor for gastric cancer, but further studies are needed to test this hypothesis.

[Research in Mexico on the health impact of environmental chemical pollutants]

This paper is intended to offer a qualitative and quantitative diagnosis on publications concerned with human health impact of exposure to environmental chemical pollutants in Mexico. The review of these subjects included scientific papers on studies carried out in Mexico, published both in Mexican and international journals. The articles were analyzed according to the following criteria: chemical pollutants, type of study and institution that conducted it, study population, design, and analysis of data. The article concludes that publications in this field are scarce. Moreover, this review showed that there is little diversity, limited methodology and an unequal distribution of the human and material resources for research. All this indicates a rudimentary level of scientific knowledge in Mexico regarding public health implications of chemical pollutants.

[Reproductive risk factors and uterine cervix cancer in Mexico City]

An epidemiological case control study nested in the Early Cancer Detection program of the Health Ministry in Mexico City was carried out to evaluate the principal reproductive risk factors associated with uterine cervix cancer. Information from 12,741 gynecological cytologies reported to the National Cancer Registry, during the period between January 2 to March 31, 1987 was studied. In this population group the most important reproductive risk factors associated with uterine cervix cancer were: multiple births (seven or more births, OR = 3.24, IC 95% = 2.20-4.76), initiation of active sex life before 14 years (OR = 1.53, 95% IC = 1.13-2.08) and late menarche (in the group with menarche after 17 year of ages OR = 3.22, 95% IC = 1.06-9.77). In relation to the Early Cancer Detection program, an important number of women made use of the program when they showed symptoms. The prevalence among women who had at least one symptom was 43.09 per cent. Women with a tumor at the cervical level at the time of the cytology were 7.76 times more likely to have of uterine cervix cancer (95% IC = 4.84-13.15). Symptoms such as dysfunctional bleeding (OR 2.79, IC 95% = 1.90-4.12), metrorrhagia (OR 2.66, 95% IC 1.83-3.86) and bloody leukorrhea (OR 2.64, 95% IC 2.05-3.38) can be relevant findings in women at high risk. The attributable fraction of higher exposure in the presence of gynecological signs and symptoms is the cervical tumor, with 87.46 per cent.(ABSTRACT TRUNCATED AT 250 WORDS)