Differential effects of obesity with and without hyperinsulinemia on plasma lipoprotein(a) concentrations in men.

To determine the association of in vivo concentrations of insulin, obesity, and gender with lipoprotein(a) [Lp(a)] levels, we used a cross-sectional population-based survey of a multistage random sample of the Mexico City adult population. We studied 423 normoglycemic, normotensive subjects from an original sample of 825, comprised of 239 men and 189 women with a mean age of 38.6 years (range, 17 to 90). All subjects were divided into 8 groups according to body mass index, fasting insulin, and gender. Lp(a) concentrations (mg/dL) were similar in obese women with and without high insulin levels (19.9 v 18.6), but hyperinsulinemic obese men had significantly lower Lp(a) levels than normoinsulinemic obese men (7.9 v 29.4). In addition, the proportion of obese men with Lp(a) concentrations of > or = 30 mg/dL was significantly higher in the normoinsulinemic than in the hyperinsulinemic (29.2% v 0.0%). The frequency distribution of Lp(a) levels was shifted to a lower range in hyperinsulinemic men compared with normoinsulinemic men. Our results show that in men, hyperinsulinemic obesity is associated with low Lp(a) levels, while obesity with normoinsulinemia is related to increased Lp(a) concentration. These observations were not found in women. These findings may explain the conflicting results reported by several studies.

Effect of the new diagnostic criteria for diabetes in the Mexico City study.

OBJECTIVE: To assess the effect of the new American Diabetes Association (ADA) diagnostic criteria for diabetes in the Mexico City survey. METHODS: The data available from the Mexico City study were included. This cross-sectional survey was conducted from January 1991 to March 1992 and involved 805 adults (20 years of age or older; mean age, 41 years). Survey procedures and results were previously published. Of the residents with diabetes, 74.2% had a previous diagnosis, and 25.8% were diagnosed on the basis of fasting plasma glucose (FPG) levels obtained during the survey. For the current report, these data were reanalyzed on the basis of the new ADA diagnostic criteria. RESULTS: The prevalence of newly diagnosed diabetes with use of the old and the new criteria was 23.1% versus 32.3% in men (P = 0.31) and 27.5% versus 36.3% in women (P = 0.32), respectively. The crude prevalence rate of diabetes increased from 8.7% to 9.3% (P = 0.42), and the age-adjusted rate increased from 10.6% to 11.2% for women (P = 0.64) and from 6.0% to 6.5% for men (P = 0.49). The prevalence of impaired FPG was 4.8%. Those patients with impaired FPG or newly diagnosed diabetes with FPG levels between 126 and 140 mg/dL had a more atherogenic risk profile than did those with normal carbohydrate metabolism. CONCLUSION: On the basis of the 1990 population census in Mexico City, the new ADA criteria will add 28,331 patients with diabetes (6.9%) to an already insufficient medical system. For those patients with impaired FPG or newly diagnosed diabetes on the basis of the new criteria, management should be focused on the control of the diverse and highly prevalent coronary risk factors.

[Risk factors for the development of germ cell tumors in children]. / Factores de riesgo para el desarrollo de tumores de células germinales en niños.

The search for risk factors for development of germ cell tumors (GCT) in children who lived in Mexico City (MC). A protective, observational, case-control study was conducted in children under 15 years of age resident in MC, insurer by the Mexican Institute of Social Security. The study population was selected between January 1st, 1990 and December 31st, 1994. Parents of the children were interviewed with a 230-items precoded questionnaire, validated previously with a pilot study. For analysis were obtained simple frequencies and odds ratios (OR) and 95% confidence interval (95%CI). There were 21 cases and 105 controls. The most significant risk factors were winter conception (OR = 7.6, 95% CI 1.5-39.3; P = 0.007); low parental education level (OR = 2.9, 95% CI 1.1-7.5; P = 0.026); and parental combined dust and electricity exposure before pregnancy (OR = 26, 95% CI 2.28-1291.86; P = 0.0007). during (OR8.58, 95% CI 0.89-106.55; P = 0.041) and after pregnancy (OR = 9.66, 95% CI 0.99-120.22; P = 0.027). There was a protective effect with repetitive infections during infancy. In conclusion, Winter conception is in accordance with infectious etiology theory of GCT development. The low parental education level and the combined exposure to dust and electricity are very important. The protective effect of repetitive infections and other factors make necessary more epidemiologic studies in this field.

Prevalence of high blood pressure and associated coronary risk factors in an adult population of Mexico City.

BACKGROUND: Several studies have addressed arterial hypertension prevalence in Mexico. However, few include an analysis of other types of hypertension and their associated risk factors. The present work describes the prevalence of high blood pressure (HBP), isolated systolic hypertension (ISH) and diastolic hypertension (DH) and their association to certain risk factors of cardiovascular disease in an adult population of Mexico City. METHODS: A cross-sectional study was performed on 825 subjects aged between 20 and 90 years, selected by multistage cluster sampling. HBP was diagnosed by previous history if systolic blood pressure was > or = 140 mmHg and/or diastolic blood pressure > or = 90 mmHg. The measurements taken included body mass index, waist-to-hip ratio, systolic and diastolic blood pressure, levels of insulin, glucose, trigylycerides, total cholesterol, high and low density lipoprotein cholesterol, and lipoprotein(a). RESULTS: Prevalence adjusted by age for HBP was 19.4%, for ISH, 4.7%, and for DH, 4.1%. Age had an important influence on HBP and ISH with a highly significant X2t. The profile of metabolic variables was modified according to sex and type of hypertension. Thus, in DH, metabolic variables were more affected than in other types of hypertension. CONCLUSIONS: Results in HBP prevalence in the present study were lower than in other surveys performed in Mexico. It must be noted, however, that much care should be taken to choose the strategy of subject selection, since results of the prevalence of a disease depend on it to a great extent. The ISH and DH and their association to risk factors must be studied thoroughly because they constitute different clinical entities.

Incidence of malignant neoplasms in children attending Social Security Hospitals in Mexico City.

An increase in neoplasms in Mexican children has been reported. In 1991, the incidence in children from Mexico City (MC) was 70 (x 10(6) child/year), although this rate might be underestimated. The aim of the present study was to estimate the incidence of malignant neoplasms in children resident in MC attending Social Security (SS) hospitals. This study was a retrospective hospital survey. All records of childhood malignant neoplasms diagnosed between 1992 and 1993 in the two SS hospitals which attend childhood neoplasms in MC were reviewed. Histopathological diagnoses were reevaluated and incidence rates (x 10(6) child/ year) in terms of age, sex, and place of residence were estimated. A total of 667 cases were found for the period of study, of which 199 corresponded to residents of MC. The neoplasms with highest prevalence were leukemias (39.2%), lymphomas (17.6%), and central nervous system tumors (12.6%). A general incidence of 94.3 was found, which was highest in children under 5 years of age. Leukemias had an incidence of 36.4, lymphomas of 15.2, and central nervous system tumors of 12.0. Prevalence was higher in boys (male/female ratio of 1.6). As for the place of residence, the highest incidence corresponded to children living in the southern areas of MC. Eighty percent of the leukemias were acute lymphoblastic, while 54% of solid neoplasms were classified as stages III and IV. In conclusion, the incidence of malignant neoplasms in children resident in MC treated at SS hospitals is consistent with that found worldwide, and also with the Latin American pattern.

Clustering of metabolic disorders and hyperinsulinemia in Mexico City.

OBJECTIVE: To investigate the relationship between fasting insulin concentrations and several metabolic and anthropometric variables in the Mexico City population. DESIGN: Cross-sectional, randomized, stratified by age, sex and economically active and inactive. SUBJECTS: 700 healthy adults, older than 20 years, 396 males and 304 females. MEASUREMENTS: Body mass index, waist to hip ratio, systolic and diastolic blood pressure, insulin, glucose, triglycerides, total, HDL and LDL cholesterol and lipoprotein(a). RESULTS: Means for age were 39 +/- 13 years for men and 41 +/- 12 for women (p < 0.05). In males, the mean values of body mass index, waist-to-hip ratio, systolic and diastolic blood pressure, triglycerides, glucose and LDL-cholesterol : HDL-cholesterol increased significantly with higher insulin levels. A significant inverse tendency was observed for the mean concentrations of HDL-cholesterol and lipoprotein(a). Age, total cholesterol and LDL-cholesterol were not related to the insulin levels. A similar pattern was observed in women, significance, however, was only obtained for the body mass index, triglycerides, glucose, HDL-cholesterol and lipoprotein(a). Age-adjusted multiple regression analysis showed that insulin was directly and independently associated to triglyceride levels and inversely with lipoprotein(a) concentrations for both sexes, and with HDL-C, only in males. CONCLUSIONS: The prevalence of insulin resistance related metabolic disorders was high in a random sample of the Mexico City population. Increased cardiovascular risk factors associated with the insulin resistance syndrome were observed with higher insulin levels, and lipoprotein(a) was inversely and significantly related to insulin. Preventive strategies are urgently needed to avoid the already increased incidence of morbidity and mortality associated to atherosclerotic disease.

High blood pressure and cardiovascular risk factors in an adult population of Mexico City. Characteristics of the studied population.

The present report is a description of the characteristics of a studied population and of the methodology used in a study performed to investigate high blood pressure prevalence and cardiovascular risk factors among the adult population of Mexico City. A cross-sectional study was conducted from January 1991 to March 1992. Random samplings of multiple stages was used and 825 adult subjects were studied in Mexico City. The following measurements were registered: blood pressure, body mass index (BMI), waist-hip ratio (WHR), total cholesterol (TC), triglycerides (TG), high density lipoproteins (HDL-C) and low density lipoproteins (LDL-C), lipoprotein (a) (Lp(a)), glucose and insulin. Personal and family history of cardiovascular illness were investigated, as well as exposure to some risk factors such as smoking, alcohol consumption and sedentarism. The response rate was 86.6%. The prevalence of high blood pressure was 21.1%, and of non-insulin dependent diabetes mellitus was 8.7%. Frequency of dyslipidemia in the studied sample was 24.4% for high TG, 23.6% for low HDL-C, 23.6% for high LDL-C, 14.9% for Lp(a) excess (Lp(a) > or = 30 mg/dl; overweight and obesity were more prevalent among women. The diversity of living conditions among the population of Mexico City was included in the sampling strategy design, not only to register the high blood pressure (HBP) frequency in each stratum but to identify other cardiovascular risk factors which could be decisive in the development of HBP. Regarding the features of the studied population, BMI did not reveal differences among men, but their TG levels were higher and HDL levels lower than those of other populations. In women, the results obtained for BMI, WHR, lipids and lipoproteins were also higher compared with the mean reported for other populations.

The prevalence of NIDDM and associated coronary risk factors in Mexico City.

OBJECTIVE: To determine the prevalence of diabetes and associated coronary risk factors in the Mexico City population. RESEARCH DESIGN AND METHODS: A sample of 805 adults was selected from Mexico City. The participants, 20-90 years of age and living in the city, were selected by the method of multistage cluster sampling with proportional allocation. Diabetes was diagnosed by previous history or if fasting blood glucose was > or = 7.8 mmol/l ( > or = 7.8 mmol/l ( > or = 140 mg/dl). RESULTS: The crude rate prevalence of NIDDM was 8.7%, with an age-adjusted rate of 10.6% for women and 6.0% for men. Age strongly influenced diabetes prevalence, with a chi 2 of risk tendency of 39.1 (P < 0.00005). A significant proportion (5.9%) of younger individuals (35-44 years of age) was affected by the disease. Diabetes was associated with advanced age, had a greater impact in the low-income group, and showed increased odds ratio for hypertension, dyslipidemias, and myocardial infarction in men and women and for obesity only in women. CONCLUSION: There is a high prevalence of NIDDM in Mexico City that also strikes a significant group of younger individuals. Associated coronary risk factors are also common and more prevalent in diabetic individuals. Current epidemiological data in Mexico and Mexican-Americans in the U.S. suggest that we may be on the ascending limb for diabetes and cardiovascular disease. There is a critical need for resources to be allocated to programs for primary and secondary prevention, which must be well structured and organized so that proper standards of care are followed to prevent progression of the disease.

[The utility of joint sensitivity and specificity curves applied to a diagnostic test]. / Utilidad de las curvas de sensibilidad y especificidad conjunta en la aplicación de una prueba de diagnóstico.

The aim of this study was to obtain the cut point to determine an individual's seronegativity with respect to measles using commercial reagents. To determine the test sensitivity, the serum of 22 individuals 21 years of age or older, and a positive history of measles (positive control group) was studied. For specificity, the serum of 22 children 15 to 24 months old, and no measles vaccination record nor positive history of measles (negative control group), was analyzed. The antibodies titer determination for both groups was done using the ELISA technique and the Brunell method, subsequently, as well as a ROC curve (Received Operating Curve). When the Brunell method was used, the cut points were 0.4090 (sensitivity 1.0 and specificity 0.95) and 0.5042 (sensitivity 0.95 and specificity 1.0). When a ROC curve was done the cut point was 0.4500, with a sensitivity and specificity of 100 per cent. It was also concluded that the latter is the best method to obtain this cut point, because it does not establish arbitrary values when the data distribution does not follow a normal pattern.

[Risk factors associated with the development of leukemia in children]. / Factores de riesgo asociados al desarrollo de leucemia en niños.

INTRODUCTION: Leukemia is the most frequent neoplasia in children; in our country it is the main cause of medical attention in children with cancer. The are different risk factors associated with the development of this kind of cancer. OBJECTIVE: To identify which of the already known factors described in the literature associated with the development of leukemia are most frequent in the pediatric population of Mexico City. MATERIAL AND METHODS: A protective case-control study was carried out using prevalent and incident cases. In two third level hospitals of Mexico City, a total of 81 children who had been diagnosed as suffering from different kind of leukemia, confirmed by biopsy of bone marrow, were select and studied. The control were 154 children from two different sources: 77 of them came from the same hospital where the cases received medical care, the selection criteria was not to have any kind of neoplasia; and 77 came from the same community where those diagnosed children cases lived, the selection criteria for this group was that they were healthy children. Both cases and community controls were visited at home and interview to complete precoded questionnaire with the different variables of the study. The information from the hospital controls was obtained during the time they stayed in the hospital. Odds ratio (OR's) for the different associations were calculated, as well as its confidence intervals at 95% (IC) accord to Cornfield and unconditioned logistic regression was carried out to control confounding variables. RESULTS: OR greater than 1 was found in those with familiar cancer background 1.93 (1.2-3.63); the mother being exposed to X-ray during pregnancy 1.89 (0.84-4.22); previous abortions before the child with leukemia was born 2.44 (1-06-5.68); being born from full term birth 2.42 (0.47-16.65); being born with weight greater that 3500 g 2.21 (1.04-4.33); being exposed to fertilizers 4.73 (1.04-24.14) and insecticides 1.93 (1.05-3.56). OR smaller than 1 was found in those who have been in a hospital because of an infectious disease during the first year of life 0.57 (0.17-1.74); to have suffered from chicken pox 0.59 (0.32-1.08). No association to parent's age or job was found. Multivariated analysis shows that the exposure to insecticide is the most important risk factor associated with the development of leukemia in children. CONCLUSIONS: We obtained positive associations to different risk factors described in the literature, having found that exposure to fertilizers is the most important risk factor and finding no association with the parent's occupation. This leads to the need of carrying out further studies to investigate, in more detail, the occupation of the father to confirm whether or not this is a risk factor.

[Residence close to high-tension electric power lines and its association with leukemia in children]. / Residencia cercana a fuentes eléctricas de alta tensión y su asociación con leucemia en niños.

INTRODUCTION: There are different risk factors which have been related to the presence of leukemia in children. In the past years one of these factors has become relevant, the risk of living in an area near to high electric voltage lines, generators of electromagnetic fields of low frequency (EMF), which can cause development of leukemia in children. OBJECTIVE: To learn whether living in an area close to EMF generator sources, electric transformers, high electric voltage distribution or transmission lines and electric substations, is a risk factor in the development of leukemia in children living in Mexico City. MATERIAL AND METHODS: A projective study of case-control was accomplished. The cases were obtained from hospitals of the third level. The diagnosis of leukemia in its different varieties was confirmed through biopsy of bone marrow. The controls were selected in the same hospital from inpatients and outpatients with different problems, except neoplasia. A total sample of 81 cases and 77 controls was analyzed. The residence of the controls and cases were visited using a questionnaire coded with the different study variables. To diminish the memory bias in relation to EMF, the subjects were shown different pictures pointing out the different sources of exposures, which were asked. Having obtained the information, different odds ratios (OR) were calculated for the different associations, as well as the confidence intervals at 95% and an unconditioned logistic regression was accomplished to know the adjusted OR. RESULTS: There were no differences between the cases and controls according to the relative who gave the information, the current age of children, the parents's age, the social class and the parent's occupation. It was found that all the generating sources of EMF, which were involved in the study, had and OR above 1. Being the highest, the ones living near the distribution or transmission wires of high voltage with an OR of 2.63 (1.26-5.36) and 2.5 (0.97-6.67) respectively. When the distance of exposure was controlled, the highest OR was for distribution lines (OR 2.12; 0.79-5.85). When the analysis was applied to persons who have moved from the residence, it was found that the OR was above 1 in all the associations, the highest being the distribution wires and with the distance the highest was the electric substations. Furthermore, the multivariate analysis showed that the risk continued only for the distribution wires. CONCLUSIONS: The EMF exposure was found positive, however this is not very precise, that is why it is necessary to carry out other studies to confirm the existence of the association and correct possible biases which could appear during the research.

[The prevalence of elevated arterial pressure and risk factors in adolescents in the Federal District of Mexico]. / Prevalencia de tensión arterial elevada y factores de riesgo en adolescentes en el Distrito Federal.

To develop studies on blood pressure (BP) of young population, such as adolescents, is important, because it is an early way to obtain information about the factors that could influence or modify the levels of BP. A group of 1,146 junior high school students from Mexico City was studied, by means of a questionnaire to identify risk factors, which were classified as: 1. inherent factors, 2. acquired risks and 3. family background. A significant association was observed related to inherent factors in scholars, mainly at monarch age with an odds ratio of 2.45; and confidence intervals of (1.05-5.63) for systolic blood pressure (SBP) and 8.81 (4.44-17.54) for diastolic blood pressure (DBP). In relation to acquired risks, there was a positive association with the use of contraceptives. As for family background there was as important association, in the following order: obesity, diabetes and hypertension. Therefore, it may be said that since early ages there are risk factors for BP; although some of them were not significantly, they can not be excluded as risk factors because there is a possibility that a longer latency period may be needed for them to act as such.

[The consistency and validity of a measurement in clinical pediatric research. Its definition, evaluation and interpretation]. / Consistencia y validez de una medición en la investigaciíon clínica pediátrica. Definición, evaluación y su interpretación.

In clinical pediatric research as in all research, one of the fundamental characteristics is the measurement of the studied features, either clinical, of laboratory or cabinet. A measurement must have two fundamental characteristics, for it to be considered as scientific: consistency and validity. The first one is centered on the variability of the measurement, which is due to the measuring instrument, to the subject or entity which is measured and to the individual or individuals who carry out the measuring, this is known as intra or interobserver variability, respectively. Validity is the fact of "actually" measuring what we want to measure. Both characteristics of measurement, are often mixed, between them and with other concepts, and this is the reason of not having a clear idea of what is the real meaning. This paper discusses the different terms that have been used for consistency and validity of a measurement. Also it points out how to assess consistency, from the validity, taking into account the measuring scale of the variables and the number of observers. Easy examples are used for the application of different formulas and for the interpretation of the results.

[Susceptibility to measles in the adolescent population of the Federal District]. / Susceptibilidad al sarampión en la población adolescente del Distrito Federal.

It is well known that in developing countries, measles disease is frequently increasing among adolescents. In Mexico, it is also thought that this problem is moving in such a way; however, this can not be proven with the statistical information at hand. For this reason a serum-survey was carried out in a sample of 870 healthy teenagers drawn from public and private secondary schools in Mexico City, in order to know if they were susceptible to measles disease and in that way make the right decisions. The information background related to the vaccination and information about previously having the disease was obtained from a questionnaire that was given to the parents of the studied teenagers. In order to get de immune state of the studied group, measles antibody titles were quantified using the ELISA technique. The findings shown that the susceptibility in this group was of 21.4%, which is certainly higher than the ones that have been found in some other countries where measles epidemics in people at this age have been well documented. Accordingly, it is thought that the displacing of this illness can be found in teenagers of Mexico City. An association was found with male sex and having the illness before. Teenagers that studied in public secondary schools reported more frequently, they had had the illness than the ones who studied at private schools. It was also found that these teenagers had a higher probability of having antimeasles antibody titles which are considered non protective; that is why it is thought these students are more likely to become ill during the adolescence stage than those who already have had the illness and the consequent protection.

[Normal values of arterial pressure in adolescent students in the Federal District, Mexico]. / Valores normales de tensión arterial en escolares adolescentes en el Distrito Federal, México.

The studies of blood pressure (BP) in the adolescence are important because the growth and development, as well as the exposure to risk factors that begins in this period gives a good opportunity to make research on the behavior of BP and its modification in adulthood. We carried out a transversal study. Our sample was made by random conglomerates, multistage; we studied 1,123 children from 12 to 15 years on Mexico City. The behavior of the BP cifers for the males was that as age increases they increase at an average of 3 mmHg per year, in females we did not find this. When we compared the percentilar values by age and sex with studies carried out in the US, we had similar results.