PON1Q192R genetic polymorphism modifies organophosphorous pesticide effects on semen quality and DNA integrity in agricultural workers from southern Mexico

Pesticide exposure, including organophosphorous (OP) insecticides, has been associated with poor semen quality, and paraoxonase (PON1), an enzyme involved in OP deactivation, may have a role on their susceptibility, due to PON1 polymorphisms. Our objective was to evaluate the role of PON1Q192R polymorphism on the susceptibility to OP toxicity on semen quality and DNA integrity in agricultural workers. A cross-sectional study was conducted in farmers with Mayan ascendancy from southeastern Mexico chronically exposed to pesticides; mostly OP. Fifty four agricultural workers (18-55 years old) were included, who provided semen and blood samples. Semen quality was evaluated according to WHO, sperm DNA damage by in situ-nick translation (NT-positive cells), PON1Q192R polymorphism by real-time PCR and serum PON1 activity by using phenylacetate and paraoxon. Two OP exposure indexes were created: at the month of sampling and during 3 months before sampling, representing the exposure to spermatids-spermatozoa and to cells at one spermatogenic cycle, respectively. PON1 192R and 192Q allele frequencies were 0.54 and 0.46, respectively. Significant associations were found between OP exposure at the month of sampling and NT-positive cells and sperm viability in homozygote 192RR subjects, and dose-effect relationships were observed between OP exposure during 3 months before sampling and sperm quality parameters and NT-positive cells in homozygote 192RR farmers. This suggests that cells at all stages of spermatogenesis are target of OP, and that there exists an interaction between OP exposure and PON1Q192R polymorphism on these effects; farmers featuring the 192RR genotype were more susceptible to develop reproductive toxic effects by OP exposure.

Maternal and paternal occupational exposure to agricultural work and the risk of anencephaly

AIMS

To evaluate the association between parental occupational exposure to agricultural work and the risk of anencephaly in three Mexican states.

METHODS

A paired case control study (1:1) was done based on records of the Epidemiological Surveillance System of Neural Tube Defects in Mexico; 151 cases of anencephaly of more than 20 weeks' gestation were selected between March 2000 and February 2001. Controls were selected from the same maternity services as those of the cases and were born alive without congenital malformations. Information was obtained from both parents by means of a general questionnaire, a food frequency questionnaire, and a specific questionnaire on occupational exposure to pesticides. Exposures were analysed with emphasis on the three months before and one month after the last menstruation periods (acute risk period (ARP)), as well as exposure prior to the above mentioned period (non-acute risk period (NARP)).

RESULTS

The children of mothers who worked in agriculture in the ARP had a greater risk of anencephaly (OR = 4.57, 95% CI 1.05 to 19.96). The risk of fathers having a child with anencephaly was greater in those who applied pesticides irrespective of whether it was done in the ARP or the NARP (OR = 2.50, 95% CI 0.73 to 8.64; and OR = 2.03, 95% CI 0.58 to 7.08, respectively).

CONCLUSIONS

These results support the hypothesis of the effect of maternal exposure to agricultural work on anencephaly and suggest that exposure of the father to pesticides in the periconceptional period or prior to this can also increase the risk of having an anencephalic child.

[Acute effects of air pollution on health: evidence from epidemiological studies]

OBJECTIVE

To summarize the evidence of acute health effects from exposure to particulate matter and ozone.

MATERIAL AND METHODS

A meta-analysis was performed using random effect models, to summarize the health effects of pollution, published in major international and Mexican journals up to June 2000.

RESULTS

Results were given as percent increase in ten units of PM10 (microgram/m3) and ozone (ppb). PM10 was found to have an effect on mortality (0.96%), hospital admissions (1.39%), emergency room visits (3.11%), respiratory symptoms (7.72%), pulmonary forced vital capacity (1.42%), and restricted activity days (7.74%). Ozone effects were equally significant.

CONCLUSIONS

These findings show the great impact that air pollutants may have on the health of populations living in large metropolis.

Assessing the health benefits of urban air pollution reductions associated with climate change mitigation (2000-2020): Santiago, São Paulo, México City, and New York City

To investigate the potential local health benefits of adopting greenhouse gas (GHG) mitigation policies, we develop scenarios of GHG mitigation for México City, México; Santiago, Chile; São Paulo, Brazil; and New York, New York, USA using air pollution health impact factors appropriate to each city. We estimate that the adoption of readily available technologies to lessen fossil fuel emissions over the next two decades in these four cities alone will reduce particulate matter and ozone and avoid approximately 64,000 (95% confidence interval [CI] 18,000-116,000) premature deaths (including infant deaths), 65,000 (95% CI 22,000-108,000) chronic bronchitis cases, and 46 million (95% CI 35-58 million) person-days of work loss or other restricted activity. These findings illustrate that GHG mitigation can provide considerable local air pollution-related public health benefits to countries that choose to abate GHG emissions by reducing fossil fuel combustion.

[Difficulties of the methods for studying environmental exposure and neural tube defects]

OBJECTIVE

To discuss the attitudes in the assessment of environmental exposures as risk factors associated with neural tube defects, and to present the main risk factors studied to date.

RESULTS

Environmental exposures have been suggested to have a roll in the genesis of birth defects. However, studies conducted in human populations have found difficulties in the design and conduction to show such an association for neural tube defects (anencephaly, espina bifida and encephalocele) because of problems raised from: a) the frequency measures used to compare time trends and communities, b) the classification of heterogeneous malformations, c) the inclusion of maternal, paternal and fetal factors as an integrated process and, d) the assessment of environmental exposures.

CONCLUSIONS

Hypothetically both maternal and paternal environmental exposures can produce damage before and after conception by direct action on the embryo and the fetus-placenta complex. Therefore, in the assessment of environmental exposures we need to take into account: a) both paternal and maternal exposures; b) the critical exposure period, three months before conception for paternal exposures and one month around the conceptional period for maternal exposures; c) quantitatively evaluate environmental exposures when possible, avoiding a dichotomous classification; d) the use of biological markers of exposure is highly recommended as well as markers of genetic susceptibility.

Predictors of death from pulmonary tuberculosis: the case of Veracruz, Mexico

OBJECTIVES

To identify factors (particularly social, economic and cultural), associated with the risk of death from pulmonary tuberculosis in Mexico.

METHODS

A case-control study of patients receiving medical attention from the official health services of Veracruz, Mexico. Cases were deaths from pulmonary tuberculosis in 1993. Controls were survivors randomly selected from the State Tuberculosis Case Registry. Next of kin provided information for both cases and controls.

RESULTS

Multivariate analysis of 161 cases and 161 controls showed an increased risk of dying for those patients who withdrew from treatment (odds ratio [OR] = 3.52), who were refused medical attention during some period of time in any health center (OR = 4.45), and who had a concomitant disease at the time of diagnosis (OR = 2.62). A linear trend with age was observed (OR = 1.02 per year), as well as a lower risk for those patients who were compliant with treatment and optimistic about surviving the disease (OR = 0.17). The risk of death was not associated with the presence of a health care unit in the town, time spent to get to the health center, or the residence of a patient in an urban area.

CONCLUSIONS

These findings indicate that deaths due to tuberculosis in this area are not related to the geographical distribution of health services but to delays in treatment after the onset of disease and to the low adherence of patients to the treatment regimen.

Blood lead levels measured prospectively and risk of spontaneous abortion

Studies of low to moderate level lead exposures have reported mixed findings regarding the risk of spontaneous abortion, despite lead's abortifacient properties at very high doses. To evaluate the risk of spontaneous abortion from low or moderate lead exposures, a nested case-control study was conducted within a cohort of pregnant women in Mexico City, 1994-1996. During their first trimester, 668 women enrolled, were interviewed, and contributed blood specimens. Pregnancies were followed by home visits or telephone calls. Spontaneous abortions before week 21 (n = 35) were matched with pregnancies that survived beyond week 20 (n = 60) on maternal age, hospital, date of enrollment, and gestational age at enrollment. Mean blood lead levels were 12.03 microg/dL for cases and 10.09 microg/dL for controls (p = 0.02). Odds ratios for spontaneous abortion comparing 5-9, 10-14, and > or =15 microg/dL with the referent category of <5 microg/dL of blood lead were 2.3, 5.4, and 12.2, respectively, demonstrating a significant trend (p = 0.03). After multivariate adjustment, the odds ratio for spontaneous abortion was 1.8 (95% confidence interval = 1.1, 3.1) for every 5 microg/dL increase in blood lead. Low to moderate lead exposures may increase the risk for spontaneous abortion at exposures comparable to US general population levels during the 1970s and to many populations worldwide today; these are far lower than exposures encountered in some occupations.

Air pollution and infant mortality in Mexico City

Historic air pollution episodes of the 1950s led to acute increases in infant mortality, and some recent epidemiologic studies suggest that infant or child mortality may still result from air pollution at current levels. To investigate the evidence for such an association, we conducted a time-series study of infant mortality in the southwestern part of Mexico City in the years 1993 to 1995 using mortality data from death registrations and air pollution measurements from a monitoring station we operated. Excess infant mortality was associated with the level of fine particles in the days before death, with the strongest association observed for the average concentration of fine particles during the period 3 to 5 days previously: a 10-microg m(-3) increase in the mean level of fine particles during these 3 days was associated with a 6.9% excess of infant deaths (95% confidence interval 2.5-11.3%). Infant mortality was also associated with the levels of nitrogen dioxide and ozone 3 to 5 days before death, but not as consistently as with particles.

Mortality and ambient fine particles in southwest Mexico City, 1993-1995

++Epidemiologic studies have focused attention on the health effects of fine particulate air pollutants <2.5 microm in diameter (PM2.5). To further characterize the potential effects of fine particles, we investigated the relationship of air pollution to mortality in Mexico City during 1993-1995. The concentration of PM2.5 was measured on a 24-hr integrated basis; concentrations of NO2 and ozone were measured hourly and reduced to 24-hr means. Daily mortality was determined from death registration records, and Poisson regression was used to model daily death counts as a function of air pollutant levels on the same and previous days, while controlling for temperature and periodic cycles. Without taking other air pollutants into account, a 10 microg/m3 increase in the level of PM2.5 was associated with a 1.4% increase in total mortality, both on the current day and 4 days after exposure [95% confidence interval (CI), 0.2-2.5]. An equivalent increase in PM2.5 was also associated with somewhat larger excesses of deaths among people over 65 years of age and from cardiovascular and respiratory causes, which occurred after a lag of 4 days. The mean concentration of ozone over a 2-day period was associated with a 1.8% increase in mortality from cardiovascular diseases. NO2 was not consistently related to mortality. Fine particles had an independent effect on mortality when modeled simultaneously with other pollutants, and the association of ozone with cardiovascular mortality was strengthened after adjusting for NO2 and PM2.5. These results support previous findings that urban air pollution at current levels leads to excess mortality and suggest that fine particles may play a causal role in producing that excess.

Mortality and ambient fine particles in southwest Mexico City, 1993-1995

++Epidemiologic studies have focused attention on the health effects of fine particulate air pollutants <2.5 microm in diameter (PM2.5). To further characterize the potential effects of fine particles, we investigated the relationship of air pollution to mortality in Mexico City during 1993-1995. The concentration of PM2.5 was measured on a 24-hr integrated basis; concentrations of NO2 and ozone were measured hourly and reduced to 24-hr means. Daily mortality was determined from death registration records, and Poisson regression was used to model daily death counts as a function of air pollutant levels on the same and previous days, while controlling for temperature and periodic cycles. Without taking other air pollutants into account, a 10 microg/m3 increase in the level of PM2.5 was associated with a 1.4% increase in total mortality, both on the current day and 4 days after exposure [95% confidence interval (CI), 0.2-2.5]. An equivalent increase in PM2.5 was also associated with somewhat larger excesses of deaths among people over 65 years of age and from cardiovascular and respiratory causes, which occurred after a lag of 4 days. The mean concentration of ozone over a 2-day period was associated with a 1.8% increase in mortality from cardiovascular diseases. NO2 was not consistently related to mortality. Fine particles had an independent effect on mortality when modeled simultaneously with other pollutants, and the association of ozone with cardiovascular mortality was strengthened after adjusting for NO2 and PM2.5. These results support previous findings that urban air pollution at current levels leads to excess mortality and suggest that fine particles may play a causal role in producing that excess.

[The case-control design in medical research]

The aim of this paper is to present a conceptual and practical framework of the case-control design in medical research. To illustrate this method, practical examples directed to clinicians and other health professionals interested in medical research are presented. The case-control method is very versatile and allows for multiple applications. Guidelines for the selection of cases and controls, and some considerations on sample size are presented. In the statistical analysis we use concrete examples of how to estimate odds ratios, confidence intervals, and methods to control for potential confounders, from stratified analysis to logistic regression.

Particulate air pollution and daily mortality: can results be generalized to Latin American countries?

OBJECTIVE

Recently, a series of reports, based on ecological analyses of routinely collected data, have shown positive associations between measures of particle concentration and daily mortality counts in various cities of the US and Europe.

MATERIAL AND METHODS

We reviewed the process of generalization of these results to Latin American countries addressing possible differences in air pollution mixtures, exposure profiles, and population susceptibility.

RESULTS

A limitation to the process of generalization is the lack of a well-established biological mechanism by which particles may act on daily mortality. Also, sources and levels of ambient air pollution as well as population characteristics and habits vary widely between Northern communities of Europe and the US, and Latin American countries, which impairs the process of generalization. However, results of studies conducted in Latin American countries suggest a similar effect to that observed in Northern countries of Europe and the US.

CONCLUSIONS

Despite uncertainty about the mechanism, there is sufficient evidence that particles are harmful for health. Control measures of particle emission are urgently needed in Latin American countries. Given the potential of misclassification of exposure, the dose-response relationship observed in Northern Europe and the US may not be adequate for Latin American populations. There is a need for a new generation of epidemiological studies including a specific assessment of exposure to fine particles and of events surrounding death.

Ozone, suspended particulates, and daily mortality in Mexico City

To investigate acute, irreversible effects of exposure to ozone and other air pollutants, the authors examined daily death counts in relation to air pollution levels in Mexico City during 1990-1992. When considered singly in Poisson regression models accounting for periodic effects, the rate ratio for total mortality associated with a 100-ppb increment in 1-hour maximum ozone concentration was 1.024 (95% confidence interval (CI) 1.011-1.039). Measures of average ozone concentration were somewhat more strongly related to mortality. The rate ratio was 1.024 (95% CI 0.984-1.062) per 100 ppb for sulfur dioxide and 1.050 (95% CI 1.030-1.067) per 100 micrograms/m3 for total suspended particulates. However, when all three pollutants were considered simultaneously, only total suspended particulates remained associated with mortality, indicating excess mortality of 6% per 100 micrograms/m3 (rate ratio = 1.058, 95% CI 1.033-1.083), consistent with observations in other cities in the United States and Europe. The authors found no independent effect of ozone, but it is difficult to attribute observed effects to a single pollutant in light of the complexity and variability of the mixture to which people are exposed. Nevertheless, particulate matter may be a useful indicator of the risk associated with ambient air pollution.

Exposure assessment for workers applying DDT to control malaria in Veracruz, Mexico

DDT has systematically been used in sanitation campaigns against malaria in Mexico. To assess chronic occupational exposure, we studied a group of workers dedicated to spraying houses to control malaria vectors in the state of Veracruz. Exposure was directly estimated for a subgroup of 40 workers by measuring DDT metabolites in adipose tissue samples and indirectly estimated for 331 workers by using a questionnaire to determine their occupational history. Participants ranged in age from 20 to 70 years, and 80% of the workers had been employed in the sanitation campaign for at least 20 years. The mean concentrations of extractable lipids found in adipose tissue samples were as follows: total DDT, 104.48 micrograms/g; p,p'-DDE, 60.98 micrograms/g; p,p'-DDT, 31.0 micrograms/g; o,p'-DDT, 2.10 micrograms/g; and p,p'-DDD, 0.95 microgram/g. The DDT metabolite p,p'-DDE was selected as the indicator of chronic exposure. An index of chronic occupational exposure was constructed according to worker position and based on the historical duration and intensity of DDT application. A linear model including this index, the use of protective gear, and recent weight loss explained 55% of the variation of p,p'-DDE concentrations in adipose tissue. By this model, the predicted values of p,p'-DDE concentration in adipose tissue for the 331 workers are between 9.56 micrograms/g and 298.4 micrograms/g of fat, with a geometric mean of 67.41 micrograms/g. These high levels of DDT in adipose tissue call for exposure prevention programs and the promotion of more secure application measures and hygiene. We also discuss the use of indirect measures of DDT exposure in epidemiological studies of health effects.

Blood lead levels in pregnant women of high and low socioeconomic status in Mexico City

This study examined the determinants of blood lead (BPb) in 513 pregnant women in Mexico City: 311 from public hospital prenatal clinics, representing primarily women of low socioeconomic status (SES), and 202 from private hospitals, primarily women of high SES. Overall, BPb levels ranged from 1.38 to 29 micrograms/dl, with geometric means of 6.7 and 11.12 micrograms/dl for women from private and public hospitals, respectively. The crude geometric means difference obtained by t-test was 4.42 (p < 0.001). BPb was measured from January 1994 to August 1995 and showed higher levels during fall and winter and lower levels during spring and summer. The main BPb determinants were the use of lead-glazed ceramics in women from public hospitals and season of the year in women from private hospitals. Consumption of tortillas (corn bread rich in calcium) decreased BPb levels in the lower SES group, but the relationship was not statistically significant (p > 0.05). Consumption of milk products significantly (p < 0.05) reduced BPb levels in the higher SES group. In 112 women whose diets were deficient in calcium, taking calcium supplements lowered their blood lead levels about 7 micrograms/dl. A predictive model fitted to these data, using the strongest predictors plus gestational age, showed a difference of 14 micrograms/dl between the best and worst scenarios in women from public hospitals. Avoiding use of lead-glazed ceramics, consuming diets rich in calcium, and, if needed, taking calcium supplements, would be expected to result in substantial lowering of BPb, especially in pregnant women of low socioeconomic status.

Ozone exposure and daily mortality in Mexico City: a time-series analysis

Daily death counts in Mexico City were examined in relation to ambient ozone levels during 1990-1992 for the purpose of investigating the acute, irreversible effects of air pollution, with emphasis on ozone exposure. Air pollution data were obtained from nine monitoring stations operated by the Departamento del Distrito Federal. Mortality data were provided by the Instituto Nacional de Estadística, Geografía, e Informática. Increases in numbers of deaths were positively associated with elevated air pollution levels on the same day and on the previous day. The magnitude of the increases was small but statistically significant, after Poisson regression models were used to adjust for temperature and long-term trends. In models using data for a single pollutant, the "crude" ratio for total mortality associated with an increase of 100 parts per billion (ppb)* in one-hour maximum ozone concentration was 1.029 (95% CI 1.015, 1.044). A moving average of ozone showed a stronger association (rate ratio [RR] = 1.048, 95% CI 1.025, 1.070), and excess mortality (an increase in the number of deaths, relative to the average on days with low pollution levels) was more evident for persons over 65 years of age. Separate analyses of the effect of elevated ozone for different areas of the city showed similar results, but they were not statistically significant. Other pollutants also were related to mortality. The RR was 1.075 (95% CI 0.984, 1.062) per 100-ppb increase for sulfur dioxide and 1.049 (95% CI 1.030, 1.067) per 100 micrograms/m3 increase in total suspended particulates (TSP) when these pollutants were considered in separate models. However, when all three pollutants were considered simultaneously, only TSP remained associated with mortality, indicating excess mortality of 5% per 100 micrograms/m3 increase [RR = 1.052, 95% CI 1.034, 1.072]. The excess mortality associated with TSP is consistent with that observed in other cities in America and Europe. This study provides some evidence that ozone is associated with all-cause mortality and with mortality among the elderly after controlling for long-term cycles. However, ozone levels exhibited little or no effect on mortality rates when other air pollutants were considered simultaneously. Particulate matter appeared to be an important pollutant; it independently predicted changes in mortality. Nevertheless, because of the complexity and variability of the mixtures to which people are exposed, it is difficult to attribute the observed effects to a single pollutant. The technical feasibility and scientific validity of isolating the effect of single pollutants in such complex mixtures requires further research and careful consideration. Given the large population living in and exposed to ambient air pollution in Mexico City and other metropolises throughout the world, these small but significant associations of mortality with air pollution indices are of public health concern.

[Sociodemographic characteristics of people who died from pulmonary tuberculosis in Veracruz, Mexico, 1993]

OBJECTIVE

We describe the socio-demographic and medical care characteristics of people who died of pulmonary tuberculosis in 1993 in the state of Veracruz, Mexico.

MATERIAL AND METHODS

Once selected, through death certificate, an interview and verbal autopsy was applied to the closest available relative.

RESULTS

A total of 300 interviews were carried out. Half of the deaths were diagnosed with tuberculosis the same year they died. Approximately half of the deceased withdrew from treatment and 40% reported abuse of alcohol consumption. Patients who died of pulmonary tuberculosis belonged to the most vulnerable social groups. 35% were illiterate or had no education, and 67% lacked a regular job. There were no differences found between those who used private medical services and those who used official or public services.

CONCLUSIONS

Important findings include the high proportion of patients diagnosed in advanced stages of the disease, alcoholism, adverse reactions to drugs as a cause of withdrawal from treatment, and other current diseases at the time of tuberculosis diagnosis.

Endemic fluorosis in San Luis Potosi, Mexico. I. Identification of risk factors associated with human exposure to fluoride

In order to identify risk factors associated with human exposure to fluoride in San Luis Potosi (SLP), Mexico, a biochemical and epidemiological study was carried out in 1992. Results from the analysis of fluoride sources showed that 61% of tap water samples had fluoride levels above the optimal level of 0.7-1.2 ppm. The levels were higher after boiling. In bottled water, fluoride levels ranged from 0.33 to 6.97 ppm. These sources are important since in SLP 82% of the children drink tap water, 31% also drink bottled water, 92% prepare their food with tap water, 44% boiled all the drinking water, and 91% used infant formula reconstituted with boiled water. The prevalence and severity of dental fluorosis in children (11-13 years old) increased as the concentration of water fluoride increased. At levels of fluoride in water lower than 0.7 ppm a prevalence of 69% was found for total dental fluorosis, whereas at levels of fluoride in water higher than 2.0 ppm a prevalence of 98% was found. In the same children, fluoride levels in urine were quantified. The levels increased as the concentration of water fluoride increased. Regressional analysis showed an increment of 0.54 ppm (P < 0.0001) of fluoride in urine for each ppm of fluoride in water. Fluoride urinary levels were higher in samples collected during the afternoon (1800) when compared with sample collected during the morning (1100). Taking together all these results, three risk factors for human exposure to fluoride in SLP can be identified: ambient temperature, boiled water, and food preparation with boiled water. These factors explain the prevalence of dental fluorosis in SLP.

[Effects of the application of the years of productive life lost index (investment-production-consumer model) on the sequence of causes of death in Mexico]

In the search for methods to support the decision making process and to maximize the benefit resulting from the health priorities, this paper discusses the investment-production-consumption model (IPC). This method attempts to quantify the socio-economic impact of mortality. This type of evaluation takes into account age at death and the potential for future productivity and thus assesses the generation of losses or gains to society, depending on the stage of life in which death occurs. The impact of different causes of death estimated by this method is illustrated from the cause of Mexico. These results are compared with the relative importance attributed by the use of mortality rates and years of potential life lost. The ordering by rates shows heart diseases, accidents and tumors as first causes of deaths. On the other hand, the indicator of years of potential life lost shows causes of death at younger ages to occupy the first place. The YPLLipc, however, gives greater importance to infections, accidents and homicides.

[Does clinical depression increase the risk of death from non-violent causes?]

Studies of the effect of depression on life expectancy have found controversial results. In the past, an excess mortality was attributed to conditions seen at psychiatric institutions. More recently, in addition to an excess mortality due to violent causes of death, some studies also found excess mortality due to non-violent and all-cause mortality. Hospital studies that evaluated this relationship are generally flawed and lack of control for potential confounders. Underlying physical illnesses could explain the excess mortality reported. On the other hand, community-based studies have studied small number of depressed subjects, and have used diverse measurements of depression which hamper comparability. This paper critically reviews recent published studies and discusses possible mechanisms for this association.

[Malnutrition as a multiple cause of death]

With the purpose of describing the role of malnutrition at death time, an analysis of multiple causes of death in children under five years-old was performed on deaths which occurred during April and May 1985 in Mexico City. A proportional mortality analysis was done taking in consideration all the causes listed on the death certificate, not only the underlying causes. The number of deaths associated to malnutrition was greater by multiple cause than by underlying cause (OR = 7.9, 95% CI 5.0-12.7, p = 0.00000). The importance of considering multiple causes of death, mainly when there are frequent diseases which are some times recorded as underlying cause of death, is also discussed.

[Therapeutic effectiveness of anticoagulation in acute myocardial infarction: a case-control study]

The main aim was to assess the role of anticoagulant therapy (AT) in reducing the mortality for patients with acute myocardial infarction (AMI). A pair-matched case-control study was designed according to three confounding factors: gender, age (+/- 5 years), and hospitalization date (+/- 13 months). Cases were defined as patients with AMI who died during hospitalization and controls were those patients with AMI who survived. Excluded from the study were patients with strong indications or contraindications for use of AT, and also those with early death (less than 12 hr). The study undertaken at the National Institute of Cardiology "Ignacio Chávez" of Mexico City and all necessary information was obtained from clinical charts of patients discharged between the period from January 1, 1975 to December 31, 1985. Complete information was accomplished for 212 pairs of cases and controls. A protective odds ratio (favoring use of AT) = 12.1 (p less than 0.0001, 95% CI 4.2-34.9) was obtained by means of a multiple logistic regression analysis by conditional method. Other variables that entered into the logistic model were: antithrombotic therapy, severity measured by Killip scale and by Norris index. Such findings support the favorable therapeutic role of AT in patients with AMI.

[Ionizing radiation at low doses and cancer: epidemiological controversy]

The carcinogenic effects of ionizing radiation at high doses are un questionable. On the other hand, the deleterious exposure effects to low doses have not been totally proven, mainly due to methodological problems and difficulty in measuring reliable dose exposure. In this paper, some recent studies examining the effects of ionizing radiation in some occupational groups are reviewed and discussed. Also, the main areas of epidemiologic controversy are stressed. For future experiences, prospective, longitudinal studies with occupational cohorts, measuring radiation exposure with adequate registry and follow-up, are suggested.

[Analysis of multiple-cause mortality: a new approach]

Due to changes in mortality patterns, cronic and degenerative diseases have become a major problem in Mexico. Description and explanation of this kind of deaths is difficult by means of a single cause of death. In order to have a better understanding of this fenomenum an analysis of 4021 deaths occurred in Mexico city during april and may in 1985 using multiple cause of death was performed, this analysis take count of all causes reported in death certificates. With the method of multiple cause we found that the number of associated deaths, for example with hypertension and nutritional deficiencies, was considerably greater that when reported as underlying cause.

[Years of potential life lost in Mexico. Applications in the planning of health services]

During health care services planning, rational and coherent information is required in order to allocate resources in accordance with local relative need. In an attempt to recognize the national condition, Stone's method was used. This is a semi-quantitative method for analysing the relationship between health care resources and need. Years of potential life lost index was used for need assessment among the states, and confronted to its Federal Public Health Investment. The optimum resource/need ratio is regarded as that pertaining to the reference population, the nation as a whole. Deviation from the optimum ratio in the states is interpreted as a manifestation of inequitable resource distribution. The results show striking differences in needs and resources. Resource/need ratio varied from 0.21 in Oaxaca to 3.79 in Distrito Federal. The states least favoured in resource sharing were Oaxaca, Puebla, Hidalgo and México. On the other hand, Tamaulipas, Baja California Sur, Quintana Roo and Distrito Federal exceeded the optimum. These indexes permit a quantitative expression of the relationship between need and resources in order to reach geographical equity.