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ABSTRACT The use of the cytome assay in monitoring studies on children has increased in recent years. For this reason, it is necessary to know the role of possible confounding factors that could affect its outcomes. The objective was to evaluate the influence of some demographic variables and diet on the baseline values of the cytome assay biomarkers in lymphocytes and buccal mucosa cells from a group of Argentine adolescents. Following the calculation of the biomarkers, a multivariate regression analysis including confounders was performed. In lymphocytes it was observed that micronuclei (MNi) had a negative association with a moderate consumption of roots and tubers, while the number of nuclear buds (NBUDs) was higher in minors not exposed to second-hand smoke (SHS). Regarding epithelial cells, MNi had a negative relationship with the intake of tropical fruits and red meat; on the contrary, this parameter increased with the moderate ingestion of legumes. In addition, oral NBUDs had a positive association with citrus and red meat consumption, whereas cereals and oil decreased its frequency. Furthermore, an increased number of binucleated cells was observed for adolescents who ate white meat and an increase in pyknotic cells for those exposed to SHS. These results revealed that in adolescents the baseline level of the cytome assay biomarkers, especially of those related to genotoxicity, can be influenced by exogenous variables, for instance, dietary habits. Thus, such factors need to be considered when carrying out biomonitoring studies on child populations.

RESUMEN El uso del ensayo de citoma en estudios de seguimiento en niños se ha incrementado en los últimos años y resulta necesario conocer el papel de posibles factores de confusión que podrían afectar sus resultados. El objetivo fue evaluar la influencia de algunas variables demográficas y de la dieta en los valores basales de los biomarcadores de este ensayo en linfocitos y células de mucosa bucal de un grupo de adolescentes argentinos. Luego del cálculo de los biomarcadores, se realizó un análisis de regresión multivariada incluyendo factores de confusión. En linfocitos se observó que los micronúcleos (MN) se asociaron negativamente con un consumo moderado de raíces y tubérculos, mientras que los brotes nucleares (BrN) aumentaron en los menores no expuestos al humo de segunda mano (HSM). En células epiteliales, los MN tuvieron una relación negativa con el consumo de frutas tropicales y carnes rojas, aunque aumentaron con el consumo moderado de legumbres. Los BrN orales tuvieron una asociación positiva con el consumo de cítricos y carnes rojas, mientras que los cereales y el aceite disminuyeron su frecuencia. Además, se encontró un mayor número de células binucleadas para quienes comieron carne blanca y un aumento de células picnóticas para los expuestos a HSM. Estos resultados revelaron que en los adolescentes el nivel basal de los biomarcadores del ensayo de citoma, especialmente de aquellos relacionados con la genotoxicidad, puede verse influenciado por variables exógenas como los hábitos alimentarios. Por lo tanto, dichos factores deben considerarse al realizar estudios de biomonitoreo en poblaciones infantiles.

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La identificación de relaciones causales es uno de los problemas fundamentales de la investigación científica en medicina y es necesaria para poder ejercerla en forma efectiva. Sin embargo, desde el punto de vista práctico es difícil establecer la existencia de relaciones causales en estudios de carácter observacional, en gran parte por la presencia de factores de confusión. El análisis a través de variables instrumentales es una de las estrategias que permite controlar el efecto confundidor y documentar la presencia de relaciones causa-efecto en estas situaciones. En este artículo, el autor resume los principales supuestos del análisis a través de variables instrumentales, haciendo foco en la aleatorización mendeliana. (AU)

The identification of causal relationships is one of the fundamental challenges in scientific research in medicine and is necessary for its effective practice. However, from a practical standpoint, establishing the existence of causal relationships in observational studies is difficult, largely due to the presence of confounding factors. Analysis through instrumental variables is one of the strategies that allows to control the confounding effect and documenting the presence of cause-and-effect relationships in these situations. In this article, the author summarizes the main assumptions of analysis through instrumental variables, with a focus on Mendelian randomization. (AU)

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BACKGROUND: The ability of SARS-CoV-2 to remain in asymptomatic individuals facilitates its dissemination and makes its control difficult. OBJECTIVE: To establish a cohort of asymptomatic individuals, change to the symptomatic status, and determine the most frequent clinical manifestations.  METHODS: Between April 9 and August 9, 2020, molecular diagnosis of SARS-CoV-2 infection was confirmed in 154 asymptomatic people in contact with subjects diagnosed with COVID-19. Nasopharyngeal swabs were performed on these people in different hospitals in Córdoba, the Caribbean area of Colombia. The genes E, RdRp, and N were amplified with RT-qPCR. Based on the molecular results and the Cq values, the patients were subsequently followed up through telephone calls to verify their health conditions. RESULTS: Overall, of 154 asymptomatic individuals, 103 (66.9%) remained asymptomatic, and 51 (33.1%) changed to symptomatic. The most frequent clinical manifestations in young people were anosmia and arthralgia. Adults showed cough, ageusia, and odynophagia; in the elderly were epigastralgia, dyspnea, and headache. Mortality was 8%. CONCLUSIONS: A proportion of 33% of presymptomatic individuals was found, of which four of them died. This high rate could indicate a silent transmission, contributing significantly to the epidemic associated with SARS-CoV-2.

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Abstract Introduction Results from studies that have investigated gender differences in neuropsychological functioning in schizophrenia have been inconsistent. Differences in the illness stage, in the demographic and clinical characteristics of the samples, and the instruments used to measure cognition may have contributed to the heterogeneity in the results. Objective Investigate the heterogeneity in the results comparing cognitive functioning in chronically ill male and female patients with schizophrenia. Method Twenty-five women and twenty-five men chronically ill patients with schizophrenia matched on age, age at illness onset, and years of education were evaluated in cognitive functioning using the WAIS-IV. Results Men showed higher scores than women on the two global measures, on the perceptual reasoning and working memory indices, and on the information, visual puzzles, digit span, and arithmetic subtests of the WAIS-IV. Cohen's d effect sizes were high for the two global measures and the two indices (d > .68). Discussion and conclusion Overall, in chronically stable patients with diagnosis of schizophrenia, women's performance on cognitive functioning was below men's when assessed with the WAIS-IV, except in the case of processing speed. This pattern of gender differences is similar to the pattern observed in healthy populations. Our results can help to clarify the heterogeneity in the results from studies on gender differences in cognitive functioning in schizophrenia and may be valuable in designing cognitive-targeted interventions for schizophrenia.

Resumen Introducción Los resultados de los estudios que han investigado diferencias de género en funcionamiento neuropsicológico en la esquizofrenia han sido inconsistentes. Diferencias en la fase de la enfermedad, en las características demográficas y clínicas de las muestras y en los instrumentos utilizados podrían explicar esa heterogeneidad. Objetivo Investigar la heterogeneidad en los resultados comparando el funcionamiento cognitivo de pacientes con diagnostico de esquizofrenia. Método Veinticinco mujeres y veinticinco hombres pacientes con diagnóstico de esquizofrenia equiparados en edad, edad al inicio de la enfermedad y nivel educativo se evaluaron en funcionamiento cognitivo utilizando la WAIS-IV. Resultados Los hombres mostraron puntuaciones más altas que las mujeres en las dos medidas globales, en los índices de razonamiento perceptivo y de memoria de trabajo y en las subtests de la WAIS-IV de información, puzles visuales, amplitud de dígitos y aritmética. Los tamaños de efecto d de Cohen fueron altos en las dos medidas globales y en los dos índices (d > .68). Discusión y conclusión En conjunto, la ejecución de las mujeres en funcionamiento cognitivo está por debajo de la de los hombres cuando se mide con la WAIS-IV, excepto en el caso de la velocidad de procesamiento. Este patrón de diferencias de género es similar al patrón observado en población sana. Nuestros resultados pueden ayudar a clarificar la heterogeneidad de resultados en los estudios sobre diferencias de género en el funcionamiento cognitivo en la esquizofrenia y podrían ser útiles en el diseño de intervenciones centradas en la cognición.

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Abstract Introduction: The low frequency of cases and deaths from the SARS-CoV-2 COVID-19 virus in some countries of Africa has called our attention about the unusual behavior of this disease. The ivermectin is considered a drug of choice for various parasitic and viral diseases and shown to have in vitro effects against SARS-CoV-2. Aims: Our study aimed to describe SARS-CoV2 infection and death rates in African countries that participated in an intensive Ivermectin mass campaign carried out to control onchocerciasis and compare them with those of countries that did not participate. Methods: Data from 19 countries that participated in the World Health Organization (WHO) sponsored African Programme for Onchocerciasis Control (APOC), from 1995 until 2015, were compared with thirty-five (Non-APOC), countries that were not included. Information was obtained from https://www.worldometers.info/coronavirus/ database. Generalized Poisson regression models were used to obtain estimates of the effect of APOC status on cumulative SARS-CoV-2 infection and mortality rates. Results: After controlling for different factors, including the Human Development Index (HDI), APOC countries (vs. non-APOC), show 28% lower mortality (0.72; 95% CI: 0.67-0.78) and 8% lower rate of infection (0.92; 95% CI: 0.91-0.93) due to COVID-19. Conclusions: The incidence in mortality rates and number of cases is significantly lower among the APOC countries compared to non-APOC countries. That a mass public health preventive campaign against COVID-19 may have taken place, inadvertently, in some African countries with massive community ivermectin use is an attractive hypothesis. Additional studies are needed to confirm it.

Resumen Introducción: La baja frecuencia de casos y muertes por el virus SARS-CoV-2 COVID-19 en algunos países de África llamó nuestra atención sobre el comportamiento inusual de esta enfermedad. La ivermectina se considera un fármaco de elección para diversas enfermedades parasitarias y virales, y se ha demostrado que tiene efectos in vitro contra el SARS-CoV-2. Objetivos: Nuestro estudio tiene el objetivo describir las tasas de infección y mortalidad del SARS-CoV-2 en los países africanos que participaron en una campaña intensiva masiva de ivermectina para el control de la oncocercosis y compararlas con las de los países que no participaron. Métodos: Los datos de 19 países que participaron en el Programa Africano para el Control de la Oncocercosis (APOC) patrocinado por la Organización Mundial de la Salud (OMS), desde 1995 hasta 2015, se compararon con 35 países que no fueron incluidos (NO APOC). La información sobre casos y muertes por COVID-19 se obtuvo de la base de datos https://www.worldometers.info/coronavirus/. Se utilizaron modelos de regresión de Poisson para obtener estimaciones del efecto del estado APOC sobre las tasas acumuladas de infección y mortalidad por SARS-CoV-2. Resultados: Después de controlar diferentes factores, incluido el Índice de Desarrollo Humano (IDH), los países APOC (frente a los no APOC) mostraron una mortalidad 28% menor (razón de tasas ajustada: RR= 0.72, IC 95%: 0.67-0.78) y una tasa de infección 8% menor (RR= 0.92, IC 95%: 0.91-0.93) por COVID-19. Conclusiones: Las tasas de mortalidad e infección son significativamente más bajas en países APOC en comparación con los países no APOC. Una campaña preventiva masiva de salud pública contra el COVID-19 pudo haber tenido lugar inadvertidamente en algunos países africanos con un uso masivo de ivermectina en la comunidad es una hipótesis atractiva. Se necesitan estudios adicionales para confirmarlo.

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Identificar el sesgo de confusión y cómo controlarlo es uno de los desafíos metodológicos más importantes en el diseño de estudios que buscan identificar la causalidad. Este sesgo está presente en cualquier análisis de la asociación entre una exposición y un resultado de interés, una asociación que puede estar sesgada o no por una tercera variable llamada confusor. Podemos diagnosticar un confusor en todos los casos en los que este crea una asociación espuria entre una variable de exposición o variable independiente y la variable de resultado o variable dependiente. Para controlar el sesgo de confusión, podemos usar diferentes métodos. Estos incluyen aquellas técnicas aplicadas en el diseño del estudio, tales como restricción, aleatorización y coincidencia, y aquellas técnicas empleadas en el análisis de datos, como la estratificación, el análisis multivariado, la estandarización, los puntajes de propensión, el análisis de sensibilidad y el inverso ponderación de probabilidad. En esta revisión, analizamos cómo identificar una variable de confusión y las principales técnicas para controlar el sesgo de confusión.

Addressing confounding bias is one of the challenges when conducting causality studies. This occurs when we report a causal association between an exposure and an outcome, when in fact it could be result of the effect of a third factor called confounding variable. That is, when a confounder variable creates a spurious relationship between the exposure or independent variable and the outcome of interest or dependent variable. By knowing the confounding variables and their association with the exposure of interest, the confounding bias could be controlled. To control for confounding bias, we can use different methods. These include techniques applied in study design, such as restriction, randomization, and coincidence, and techniques used in data analysis, such as stratification, multivariate analysis, standardization, propensity scores, analysis sensitivity and the inverse probability weighting. In this review, we discuss how to identify a confounding variable and the main techniques for controlling for confounding bias.

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INTRODUCTION: The low frequency of cases and deaths from the SARS-CoV-2 COVID-19 virus in some countries of Africa has called our attention about the unusual behavior of this disease. The ivermectin is considered a drug of choice for various parasitic and viral diseases and shown to have in vitro effects against SARS-CoV-2. AIMS: Our study aimed to describe SARS-CoV2 infection and death rates in African countries that participated in an intensive Ivermectin mass campaign carried out to control onchocerciasis and compare them with those of countries that did not participate. METHODS: Data from 19 countries that participated in the World Health Organization (WHO) sponsored African Programme for Onchocerciasis Control (APOC), from 1995 until 2015, were compared with thirty-five (Non-APOC), countries that were not included. Information was obtained from https://www.worldometers.info/coronavirus/ database. Generalized Poisson regression models were used to obtain estimates of the effect of APOC status on cumulative SARS-CoV-2 infection and mortality rates. RESULTS: After controlling for different factors, including the Human Development Index (HDI), APOC countries (vs. non-APOC), show 28% lower mortality (0.72; 95% CI: 0.67-0.78) and 8% lower rate of infection (0.92; 95% CI: 0.91-0.93) due to COVID-19. CONCLUSIONS: The incidence in mortality rates and number of cases is significantly lower among the APOC countries compared to non-APOC countries. That a mass public health preventive campaign against COVID-19 may have taken place, inadvertently, in some African countries with massive community ivermectin use is an attractive hypothesis. Additional studies are needed to confirm it.

INTRODUCCIÓN: La baja frecuencia de casos y muertes por el virus SARS-CoV-2 COVID-19 en algunos países de África llamó nuestra atención sobre el comportamiento inusual de esta enfermedad. La ivermectina se considera un fármaco de elección para diversas enfermedades parasitarias y virales, y se ha demostrado que tiene efectos in vitro contra el SARS-CoV-2. OBJETIVOS: Nuestro estudio tiene el objetivo describir las tasas de infección y mortalidad del SARS-CoV-2 en los países africanos que participaron en una campaña intensiva masiva de ivermectina para el control de la oncocercosis y compararlas con las de los países que no participaron. MÉTODOS: Los datos de 19 países que participaron en el Programa Africano para el Control de la Oncocercosis (APOC) patrocinado por la Organización Mundial de la Salud (OMS), desde 1995 hasta 2015, se compararon con 35 países que no fueron incluidos (NO APOC). La información sobre casos y muertes por COVID-19 se obtuvo de la base de datos https://www.worldometers.info/coronavirus/. Se utilizaron modelos de regresión de Poisson para obtener estimaciones del efecto del estado APOC sobre las tasas acumuladas de infección y mortalidad por SARS-CoV-2. RESULTADOS: Después de controlar diferentes factores, incluido el Índice de Desarrollo Humano (IDH), los países APOC (frente a los no APOC) mostraron una mortalidad 28% menor (razón de tasas ajustada: RR= 0.72, IC 95%: 0.67-0.78) y una tasa de infección 8% menor (RR= 0.92, IC 95%: 0.91-0.93) por COVID-19. CONCLUSIONES: Las tasas de mortalidad e infección son significativamente más bajas en países APOC en comparación con los países no APOC. Una campaña preventiva masiva de salud pública contra el COVID-19 pudo haber tenido lugar inadvertidamente en algunos países africanos con un uso masivo de ivermectina en la comunidad es una hipótesis atractiva. Se necesitan estudios adicionales para confirmarlo.

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The COVID-19 pandemic has produced an endless stream of information in relation to data, analysis and projections of all aspects of this disease. One of the characteristics of scientific information is that it is full of uncertainties, which are not correctly disclosed to the general population. In this essay, we describe the main cognitive biases that cause people to modify their perception of risk, where the most important are memory, novelty, and emotionality or affection. In addition, we review frequent errors that have been made in terms of collection, dissemination and analysis of information by scientific communicators, experts in other areas and the media in general. Ideally, these biases and confounders should be known to all who participate in the flow of information on the health problems of this pandemic, in order to integrate the uncertainty inherent in the data and the critical analysis of the information received.

La pandemia COVID-19 ha producido un caudal interminable de información en relación a datos, análisis y proyecciones de todos los aspectos de esta enfermedad. Una de las características de la información científica es que está llena de incertidumbres, las que no se divulgan correctamente a la población general. En este ensayo, hacemos una descripción de los principales sesgos cognitivos que hacen que las personas modifiquen su percepción de riesgo donde los más importantes son el de memoria, de novedad y emocionalidad o afecto. Además, revisamos errores frecuentes que se pueden cometer en términos de recolección, difusión y análisis de la información de parte de comunicadores científicos, expertos en otras áreas y medios de comunicación en general. Idealmente, estos sesgos y confundentes deben ser conocidos por todos los que participan en el flujo de información de los problemas de salud de esta pandemia, de manera de poder integrar la incertidumbre inherente a los datos y el análisis crítico de la información que se recibe.

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OBJECTIVES: To evaluate the state of mental health and its relation with associated factors among nursing students. METHODS: A cross-sectional study was conducted with 130 students from the Nursing and Midwifery College affiliated to the University of Medical Sciences of Shiraz (Iran). Data was collected through a document that included information on the demographic characteristics, the mean grades of the practical assignments and of the total (practical and theoretical assignments), and the Goldberg Health Questionnaire (GHQ-28) that measures symptoms grouped into four dimensions (somatic symptoms, anxiety and insomnia, social dysfunction, and depression). RESULTS: Most of the participants (65.1%) were women; 5.3% were between 21 and 22 years of age, 84.5% were single, and 33.3% were in the sixth semester; 68.5% of the students had problems with mental health. By dimensions of the GHQ-28, it was found that 7.7% had somatic symptoms, 13.8% symptoms of anxiety and sleep disorders, 52.3% social dysfunction, and 6.2% depression. Males had a higher score of depression than females, and being single was related with higher scores of physical symptoms, anxiety and insomnia, and depression, compared with those who were married. An inverse relationship was found between the GHQ-28 average score and the semester, the grade in practical assignments, and the total grade for physical symptoms and anxiety and insomnia. CONCLUSIONS: There is a high proportion of nursing students with suspected mental health disorder. Some demographic and academic factors are related with the mental health of students and must be kept in mind by the institutions training future nurses.

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Os métodos de escore de propensão são a probabilidade de um sujeito receber um tratamento condicional em um conjunto de características de base (confundidores), sendo usado para comparar pacientes com distribuição similar de fatores de confusão, de modo que a diferença nos resultados forneça estimativa imparcial do efeito do tratamento. Esta revisão mostra os conceitos básicos dos escore de propensão e fornece orientação na implementação de métodos de propensão, além de outros, como estratificação, ponderação e ajuste de covariáveis, tornando-se uma guia prático para o clínico

The propensity score methods are the probability of a subject receiving conditional treatment on a set of baseline characteristics (confounders), and are used to compare patients with similar confounding distributions, so that the difference in results provides an unbiased estimate of the treatment effect. This review shows the basic concepts of propensity scores, and provides guidelines for the implementation of propensity methods, and others based on it, such as stratification, weighting, and adjustment of covariables, becoming a practical guide for the clinician

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The association between air pollution and suicide has recently been under examination, and the findings continue to be contradictory. In order to contribute evidence to this still unresolved question, the objective of the present study was to evaluate the association between air quality and daily suicides registered in Mexico City (MC) between 2000 and 2016. Air quality was measured based on exposure to particulate matter under 2.5 and 10 micrometers (µm) (PM2.5 and PM10, respectively), ozone (O3), nitrogen dioxide (NO2), and sulfur dioxide (SO2), adjusting for weather variables (air temperature and relative humidity), and holidays. To this end, an ecologic time series analysis was performed using a Poisson regression model conditioned by time and stratified by gender and age groups. Models were also generated to explore the lagged and accumulative effects of air pollutants, adjusted by weather variables. The effects of the pollutants were very close to the null value in the majority of the models, and no accumulative effects were identified. We believe these results, in this case, no evidence of a statistical association, contribute to the current debate about whether the association between air pollution and suicide reported in the scientific literature reflects an actual effect or an uncontrolled confounding effect.

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Background: Confusion in observational epidemiological studies distorts the relationship between exposure and event. "Step by step" regression models, diverts the decision to a statistical algorithm with little causal basis. Directed Acyclic Graphs (DAGs), qualitatively and visually assess the confusion. They can complement the decision on confounder control during statistical modeling. Aim: To evaluate the minimum set of confounders to be controlled in a cause-effect relationship with the use of "step-by-step regression" and DAGs, in a study of arsenic exposure. Material and Methods: We worked with data from Cáceres et al., 2010 in 66 individuals from northern Chile. The interindividual variability in the urinary excretion of dimethyl arsenic acid attributable to the GSTT1 polymorphism was estimated. A causal DAG was constructed using DAGitty v2.3 with the list of variables. A multiple linear regression model with the step-by-step backwards methodology was carried out. Results: The causal diagram included 12 non-causal open pathways. The minimum adjustment set corresponded to the variables "sex", "body mass index" and "fish and seafood ingest". Confusion retention of the multivariate model included normal and overweight status, gender and the interaction between "water intake" and GSTT1. Conclusions: The use of DAG prior to the modeling would allow a more comprehensive, coherent and biologically plausible analysis of causal relationships in public health.

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BACKGROUND: Recent epidemiological studies have suggested that air pollution could be associated with suicide. However, other studies have criticized these results for being analytically weak and not taking into account potential confounding factors. As such, further studies examining the relationship under diverse contexts are necessary to help clarify this issue. This study explored the association between specific air pollutants (NO2, SO2, PM10, PM2.5, CO and O3) and suicide incidence in four Colombian cities after adjusting for climatic variables and holidays. METHODS: A time series of daily suicides among men and women living in Bogota, Medellin, Cali and Bucaramanga was generated using information from the National Administrative Department of Statistics (DANE) for the years 2011-2014. At the same time, the average daily concentration of each air pollutant for each city was obtained from monitoring stations belonging to the National Air Quality Surveillance System. Using this information together, we generated conditional Poisson models (stratified by day, month and year) for the suicide rate in men and women, with air pollutants as the principal explanatory variable. These models were adjusted for temperature, relative humidity, precipitation and holidays. RESULTS: No association was found between any of the examined pollutants and suicide: NO2 (IRR:0.99, 95% CI: 0.95-1.04), SO2 (IRR:0.99, 95% CI: 0.98-1.01), PM10 (IRR:0.99, 95% CI:0.95-1.03), PM2.5 (IRR:1.01, 95% CI: 0.98-1.05), CO (IRR:1.00, 95% CI:1.00-1.00) and O3 (IRR: 1.00, 95% CI: 0.96-1.04). In the same way, no association was found in stratified models by sex and age group neither in lagged and cumulative effects models. CONCLUSIONS: After adjusting for major confounding factors, we found no statistically significant association between air pollution and suicide in Colombia. These "negative" results provide further insight into the current discussion regarding the existence of such a relationship.

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Pesticides are a complex mixture of chemicals used to protect crops from a number of pests and diseases. They have been considered as potential mutagenic agents. This study aims at evaluation of the mutagenic effect of pesticide exposure to agricultural workers through chromosomal aberrations (CA) and micronucleus (MN) assay in peripheral blood lymphocytes and oral mucosal cells, respectively. The exposed group was consisted with 97 farmers, while the control (un-exposed) group consisted of 55. The results showed a significant (p < 0.05) increase in frequency of CA and MN in the exposed group. Both CA and MN profiles were linked to a significant (p < 0.05) co-relation with the confounding factors such as smoking habits, alcohol, vegetables, tea/coffee, vitamins, and sweetener consumptions. More cytogenetic events were denoted in smoking and alcohol consumption as well as non-personal protective equipment (non-PPE) and low/no vegetables user farmers. In conclusion, a deficiency of dietary and medicaments-derived antioxidants, while consumption of alcohol and tobacco, as well as effects of radiation, heavy metal poisoning (especially from sweeteners), and non-PPE using habits, may contribute cytogenetic damage to the workers.

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Because the real-world impact of new vaccines cannot be known before they are implemented in national programs, post-implementation studies at the population level are critical. Studies based on analysis of hospitalization rates of vaccine-preventable outcomes are typically used for this purpose. However, estimates of vaccine impact based on hospitalization data are particularly prone to confounding, as hospitalization rates are tightly linked to changes in the quality, access and use of the healthcare system, which often occur simultaneously with introduction of new vaccines. Here we illustrate how changes in healthcare delivery coincident with vaccine introduction can influence estimates of vaccine impact, using as an example reductions in infant pneumonia hospitalizations after introduction of the 10-valent pneumococcal conjugate vaccine (PCV10) in Brazil. To this end, we explore the effect of changes in several metrics of quality and access to public healthcare on trends in hospitalization rates before (2008-09) and after (2011-12) PCV10 introduction in 2010. Changes in infant pneumonia hospitalization rates following vaccine introduction were significantly associated with concomitant changes in hospital capacity and the fraction of the population using public hospitals. Importantly, reduction of pneumonia hospitalization rates after PCV10 were also associated with the expansion of outpatient services in several Brazilian states, falling more sharply where primary care coverage and the number of health units offering basic and emergency care increased more. We show that adjustments for unrelated (non-vaccine) trends commonly employed by impact studies, such as use of single control outcomes, are not always sufficient for accurate impact assessment. We discuss several ways to identify and overcome such biases, including sensitivity analyses using different denominators to calculate hospitalizations rates and methods that track changes in the outpatient setting. Employing these practices can improve the accuracy of vaccine impact estimates, particularly in evolving healthcare settings typical of low- and middle-income countries.

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Background: Pap smear coverage in Chile has gradually decreased in the last years, from 67% to 59%, making it necessary to determine the causes of this decline. Aim: To analyze the relationship between the characteristics of the cervical cancer screening target population in the public health care system and the percentage of PAP coverage. Material and Methods: This study was carried out in women aged between 25 and 64 years, belonging to a public health care system and registered in any of the eight primary healthcare centers of a Metropolitan Santiago low income community. The analysis considered information from the recruitment database (n = 6,058) and interviewed women database (n = 1,042). Results: In 52% of cases there were difficulties in recruiting women, mainly due to wrong addresses. Among contacted women, 4.1% had a hysterectomy or had cervical cancer and 1.4% were dead. When analyzing the variable “adherence to cervical cancer screening” in the interviewed women, 76.8% reported to comply with the ministerial guidelines. From that group, 20.5% reported to attend screening at the private health care system. Seventy seven percent of women who had timely screening visits, reported attending screening periodically every 3 years or less. Conclusions: Pap smear coverage must be analyzed considering the different factors that affect it. Among the latter, the exclusion of some women from the target population and performing the screening in private clinics stand out.

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Introducción. La dieta se reconoce como segunda causa evitable relacionada con el desarrollo de cáncer. No obstante, dado su naturaleza multicausal, al estudiar la relación cáncer-dieta deben considerarse otros factores con potencial efecto confusor para evitar sesgos en estimaciones de riesgo. Objetivos. a) Identificar el efecto confundente del nivel de actividad física, hábito de fumar y nivel socioeconómico en la relación cáncer colorrectal (CCR) y dieta; b) Valorar el riesgo de factores alimentarios asociados a CCR, considerando las variables confundentes identificadas. Metodología. Se condujo un estudio caso-control (n=319; 102 casos de CCR, 217 controles) en Córdoba, Argentina (2006-2011). Se realizó un análisis bivariado entre variables alimentarias de interés y presencia de CCR, estimando ORs como medida de asociación. Luego, mediante análisis de Mantel-Haenszel, se estratificó por potenciales variables confundentes. Finalmente, se construyeron modelos de regresión logística múltiple, incluyendo las confundentes. Resultados. Se verificó efecto confusor del nivel socioeconómico en relación al consumo de carnes rojas cocidas, fibra y etanol, y de la actividad física en cuanto al consumo de fibra alimentaria. Controlando por dichos efectos, no se encontró asociación (OR 0,71; IC95 por ciento 0,31-1,62) entre la ingesta de fibra y la patología, y se observó un efecto promotor (OR 1,75; IC95 por ciento 0,95- 2,60) del nivel socioeconómico bajo y de la ingesta energética diaria (OR 1,0003; IC95 por ciento 1,00008-1,0006). Conclusión. Se reconoce el nivel socioeconómico y la actividad física como potenciales variables confusoras en el estudio de la relación CCR y alimentación en Argentina. Se recomienda considerarlas como variables de ajuste al realizar análisis de riesgos alimentarios.

Introduction. Diet is the second preventable cause related to the development of cancer. Given its multi-causal nature, in studying the relationship between cancer and diet, other factors with potential confounding effect must be considered to avoid bias in risk estimates. Objectives: a) Identifying the confounding effect of physical activity level, smoking habits and socioeconomic status in the relationship between colorectal cancer and cooked red meat, fiber and alcohol intake; b) Assessing the effect of dietary factors on the occurrence of colorectal cancer, considering the confounding variables identified. Methods. A case-control study was conducted (102 cases with colorectal cancer and 217 controls) in Cordoba, Argentina, over 2006-2011. A bivariate analysis, between food variables and the presence of colorectal cancer, and a Mantel-Heanzel analysis, stratifying by the potential confounders, were conducted. Finally, multiple logistic regression models were constructed, including the confounding variables. Results. Confounding effect of the socioeconomic status related to cooked red meat, fiber and alcohol intake, and physical activity level was verified. There was no association between fiber intake and colorectal cancer (OR 0,71; IC95 percent 0,31-1,62), while a promoting effect of low socioeconomic status (OR 1,75; IC95 percent 0,95-2,60), and daily energy intake (OR 1,0003; IC95 percent 1,00008-1,0006) were found. Conclusion. It is recommended to consider socioeconomic status and physical activity as adjusted factors when conducting food risk analysis in the study of the relationship between colorectal cancer and diet in Argentina.

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