Trends of Antihypertensive, Antidiabetic, and Nonsteroidal Anti-Inflammatory Drugs Use among the Health Workers Cohort Study, Mexico 2004 to 2018.

Background: Hypertension and type 2 diabetes (T2D) are the most prevalent noncommunicable diseases in Mexico and worldwide. According to international practice management guidelines, the principal chronic management therapy is daily oral medication. Aim: We aim to describe the trends of antihypertensive, antidiabetic, and nonsteroidal anti-inflammatory (NSAID) drugs use among the Mexican adult population from 2004-2018. Methods: We analyzed data from the Health Workers Cohort Study (HWCS) for males and females aged >18 years. We calculated the prevalence of chronic diseases and utilization for every kind of antihypertensive, antidiabetic, and NSAIDs (measured by self-reported utilization) at baseline and two follow-ups (2004, 2010, and 2017). Trends were analyzed using Fisher's exact test. Results: Hypertension prevalence increased from 19.8 to 30.3%, higher than T2D prevalence from 7.0 to 12.8% through fourteen years of follow-up. Like the self-reported dual therapy, the proportion of patients using beta-blockers and angiotensin II receptor blockers increased. Regarding T2D, the prevalence of metformin utilization increased to 83.9%. The utilization of common NSAIDs, mainly for muscular pain, remained around 13 to 16%. Conclusions: Our findings showed a changing prevalence of drug utilization for hypertension and T2D between 2004 and 2018 and consistent use of NSAIDs in the adult Mexican population.

Exposure to the pesticide DDT and risk of diabetes and hypertension: Systematic review and meta-analysis of prospective studies.

BACKGROUND: Experimental evidence suggests that p,p'-DDE might be involved in the development of diabetes and hypertension (HTN); however, the evidence in humans is inconclusive. OBJECTIVE: To summarize the epidemiological evidence for the association of p,p'-DDT exposure and its breakdown products with the risk of diabetes and HTN from prospective studies. METHODS: We performed a systematic review and meta-analysis based on the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement. Eligible studies (prospective) were search in PubMed, Web of Science, EBSCO, and SciELO databases (July 11, 2020). Different search algorithms were used for diabetes and HTN. Pooled odds ratios (ORs) were estimated from meta-analysis with random effects for each exposure and outcome. RESULTS: A total of 23 prospective studies were included in this review, 16 assessed diabetes and seven HTN; very few measured p,p'-DDT. Exposure to p,p'-DDE was associated with a slightly increased risk of type 2 diabetes (T2D) (pooled OR = 1.44; 95%CI: 1.00, 2.07; p = 0.049) and HTN (pooled OR = 1.21; 95%CI: 1.07, 1.38). Dose-response meta-analysis suggested a non-linear relation between p,p'-DDE and T2D. Exposure to p,p'-DDE was not associated with gestational diabetes (pooled OR = 1.01; 95%CI: 0.94, 1.09); similarly, p,p'-DDT was not associated with T2D (pooled OR = 1.03; 95%CI: 0.79, 1.35). CONCLUSIONS: Evidence from prospective studies suggests that exposure to p,p'-DDE, the main breakdown product of p,p'-DDT, might increase the risk of developing T2D; such increase may be apparent only at low levels. Exposure to p,p'-DDE may also increase the risk of having HTN; however, further evidence is required.

Marcadores de funcionamiento renal en pacientes infectados por SARS-CoV-2. Revisión rápida de la literatura.

 Objetivo. Resumir la evidencia científica sobre las altera-ciones renales asociadas con la infección por SARS-CoV-2. Material y métodos. Se realizó una revisión rápida con la metodología Cochrane. Resultados. La enfermedad renal crónica (ERC) preexistente en pacientes con SARS-CoV-2 varió de 1 a 38% y la lesión renal aguda (LRA), de 2.9 a 86.4%. El pronóstico de la infección fue peor en pacientes con ERC y en aquellos con reserva renal remanente (RRR) intacta que desarrollaron LRA. El riesgo de muerte fue mayor (riesgo relativo combinado = 1.49; IC95%: 1.09-2.04) en pacientes infectados por SARS-CoV-2 con ERC preexistente. Los mar-cadores de RRR mostraron alteraciones en pacientes con SARS-CoV-2 graves y fatales; el marcador más utilizado fue la creatinina sérica. Conclusiones. La evidencia científica muestra la relevancia de la evaluación y monitoreo perma-nente de la RRR en pacientes hospitalizados por SARS-CoV-2 para mejorar el pronóstico de aquellos con ERC preexistente, así como de aquellos sin ERC que desarrollan LRA.

[Intimate partner violence and depression among adult women working in a health facility in Mexico]. / Violencia de pareja y depresión en mujeres que trabajan en una institución de salud de México.

OBJECTIVE: To assess the effect of intimate partner violence on the risk of depression and depressive symptoms among adult women. METHOD: We analyzed data from the Mexican Health Workers' Cohort study (n=470). Type and severity of intimate partner violence was ascertained between 2004 and 2011. Self-reported medical diagnosis of depression (2011) was the main outcome; depressive symptoms ascertained with the Centre for Epidemiologic Studies-Depression (CES-D) scale was the secondary outcome. Random-effects regressions were run to model the risk of depression (logistic) and depressive symptoms (linear) in relation to intimate partner violence. RESULTS: 41.9% women experienced intimate partner violence at baseline. The incidence of depression was 7.2%. The risk of depression increased with any type of IPV (adjusted odds ratio [aOR]=2.9; 95% confidence interval [95%CI]: 1.4-6.2) and with physical (aOR=4.3; 95%CI: 1.8-10.1), psychological (aOR=3.1; 95%CI: 1.4-6.6) and sexual (aOR=3.1; 95%CI: 1.2-8.2) violence. Depressive symptoms (CES-D) increased slightly with physical and sexual intimate partner violence. CONCLUSIONS: Intimate partner violence was associated with a higher risk of depression in this sample of women working in a Mexican health facility. Our results indicate the need to develop infrastructure, to implement strategies of attention and counselling, and to provide a safe environment in the workplace for women who experience intimate partner violence.

Marcadores de funcionamiento renal en pacientes infectados por SARS-CoV-2. Revisión rápida de la literatura / Markers of kidney function among SARS-CoV-2 infected patients. A rapid review of the literature

Resumen Objetivo: Resumir la evidencia científica sobre las alteraciones renales asociadas con la infección por SARS-CoV-2. Material y métodos: Se realizó una revisión rápida con la metodología Cochrane. Resultados: La enfermedad renal crónica (ERC) preexistente en pacientes con SARS-CoV-2 varió de 1 a 38% y la lesión renal aguda (LRA), de 2.9 a 86.4%. El pronóstico de la infección fue peor en pacientes con ERC y en aquellos con reserva renal remanente (RRR) intacta que desarrollaron LRA. El riesgo de muerte fue mayor (riesgo relativo combinado = 1.49; IC95%: 1.09-2.04) en pacientes infectados por SARS-CoV-2 con ERC preexistente. Los marcadores de RRR mostraron alteraciones en pacientes con SARS-CoV-2 graves y fatales; el marcador más utilizado fue la creatinina sérica. Conclusiones: La evidencia científica muestra la relevancia de la evaluación y monitoreo permanente de la RRR en pacientes hospitalizados por SARS-CoV-2 para mejorar el pronóstico de aquellos con ERC preexistente, así como de aquellos sin ERC que desarrollan LRA.

Abstract: Objective: To summarize the scientific literature on kidney abnormalities associated with SARS-CoV-2 infection. Materials and methods: It was conducted a rapid review using the Cochrane methodology. Results: Pre-existing chronic kidney disease (CKD) in SARS-CoV-2 infected patients ranged from 1-38% and acute kidney injury (AKI) ranged from 2.9-86.4%. The prognosis of patients with SARS-CoV-2 infection was worse among those with CKD and those with normal remnant kidney function (RKF) that developed AKI. The risk of death was higher (pooled risk ratio =1.49; 95%CI: 1.09-2.04) among SARS-CoV-2 infected patients with pre-existing CKD. The RKF markers showed alterations among severe and non-surviving SARS-CoV-2 patients; the most common marker was serum creatinine. Conclusions: The scientific evidence shows the relevance of the evaluation and permanent monitoring of the RKF in SARS-CoV-2 hospitalized patients to improve the prognosis of those with pre-existing CKD as well as the prognosis of those without CKD who develop AKI.

[Predictors of kidney function in a cohortof Mexican adults]. / Predictores de la función renal en una cohorte de adultos mexicanos.

OBJECTIVE: Our aim was to examine prospectively predictors of subclinical renal alterations among adults without chronic kidney disease. MATERIALS AND METHODS: We analyzed data from a cohort of Mexican adults (n=757). Kidney function (2010) was assessed with the estimated glomerular filtration rate (eGFR-Cr), serum creatinine and uric acid. Predictors of each kidney function marker (2004) were identified with linear and logistic regression models. RESULTS: 33% had an eGFR-Cr 40 years old and users of antihypertensive medication; and higher among those with a high protein intake. Serum creatinine predictors were similar to those observed for eGFR-Cr. Uric acid decreased in men, among those with obesity, hypertension and high cholesterol. CONCLUSIONS: Conventional kidney function biomarkers are useful to identify subclinical alterations. Some predictors of kidney function are potentially modifiable, therefore susceptible for intervention among high-risk groups.

OBJETIVO: Examinar prospectivamente los predictores de alteraciones subclínicas de la función renal en adultos sin diagnóstico previo de enfermedad renal crónica. MATERIAL Y MÉTODOS: Se analizaron datos de una cohorte de adultos mexicanos (n=757). La función renal (2010) se midió mediante la tasa de filtración glomerular estimada (TFGECr), creatinina y ácido úrico séricos. Los predictores (2004) se identificaron con modelos de regresión lineal y logística. RESULTADOS: Se clasificó 33% con TFGE-Cr disminuida.La TFGE-Cr fue menor en hombres, en >40 años y en usuarios de antihipertensivos; y fue mayor en aquellos con consumo proteico alto. Los predictores de la creatinina fueron similares a los de la TFGE-Cr. El ácido úrico disminuyó en participantes hombres, con obesidad, hipertensión e hipercolesterolemia. CONCLUSIONES: Los biomarcadores séricos convencionales son útiles para identificar alteraciones subclínicas de la función renal. Algunos predictores de la función renal son potencialmente modificables, por tanto susceptibles de intervención.

Predictores de la función renal en una cohorte de adultos mexicanos / Predictors of kidney function in a cohort of Mexican adults

Resumen: Objetivo: Examinar prospectivamente los predictores de alteraciones subclínicas de la función renal en adultos sin diagnóstico previo de enfermedad renal crónica. Material y métodos: Se analizaron datos de una cohorte de adultos mexicanos (n=757). La función renal (2010) se midió mediante la tasa de filtración glomerular estimada (TFGE-Cr), creatinina y ácido úrico séricos. Los predictores (2004) se identificaron con modelos de regresión lineal y logística. Resultados: Se clasificó 33% con TFGE-Cr disminuida. La TFGE-Cr fue menor en hombres, en >40 años y en usuarios de antihipertensivos; y fue mayor en aquellos con consumo proteico alto. Los predictores de la creatinina fueron similares a los de la TFGE-Cr. El ácido úrico disminuyó en participantes hombres, con obesidad, hipertensión e hipercolesterolemia. Conclusión. Los biomarcadores séricos convencionales son útiles para identificar alteraciones subclínicas de la función renal. Algunos predictores de la función renal son potencialmente modificables, por tanto susceptibles de intervención.

Abstract: Objectives: Our aim was to examine prospectively predictors of subclinical renal alterations among adults without chronic kidney disease. Materials and methods: We analyzed data from a cohort of Mexican adults (n=757). Kidney function (2010) was assessed with the estimated glomerular filtration rate (eGFR-Cr), serum creatinine and uric acid. Predictors of each kidney function marker (2004) were identified with linear and logistic regression models. Results: 33% had an eGFR-Cr <90 ml/min/1.73 m2. eGFR-Cr was lower among men, those >40 years old and users of antihypertensive medication; and higher among those with a high protein intake. Serum creatinine predictors were similar to those observed for eGFR-Cr. Uric acid decreased in men, among those with obesity, hypertension and high cholesterol. Conclusion: Conventional kidney function biomarkers are useful to identify subclinical alterations. Some predictors of kidney function are potentially modifiable, therefore susceptible for intervention among high-risk groups.

Patterns of beverage consumption and risk of CHD among Mexican adults.

CHD is becoming an increasing priority worldwide, as it is one of the main causes of death in low- and middle-income countries lately. This study aims to evaluate the association between beverage consumption patterns and the risk of CHD among Mexican adult population. We performed a cross-sectional analysis using data from 6640 adults participating in the Health Workers' Cohort Study. Factor analysis was performed to identify beverage patterns using sex-specific Framingham prediction algorithms to estimate CHD risk. The prevalence of moderate to high CHD risk was 17·8 %. We identified four major beverage consumption patterns, which were categorised as alcohol, coffee/tea, soft drinks and low-fat milk. We observed a lower risk of CHD (OR=0·61; 95 % CI 0·46, 0·80; and OR=0·58; 95 % CI 0·43, 0·79, respectively) among participants in the upper quintile of alcohol or low-fat milk consumption compared with those in the bottom quintile. In contrast, a higher consumption of soft drinks was positively associated with CHD risk (OR=1·64; 95 % CI 1·21, 2·20) when compared with other extreme quintiles. Finally, coffee/tea consumption was not significantly associated with CHD risk. Our findings suggest that a beverage pattern characterised by a higher intake of sugar-sweetened beverages may be associated with an increased risk of CHD among the Mexican adult population, whereas patterns of moderate alcohol intake and low-fat milk may be associated with a reduced risk.

Influence of mealtime habits on the risk of weight gain and obesity in Mexican adults.

OBJECTIVE: To prospectively examine the extent to which mealtime habits influences the risk of weight gain and obesity in Mexican adults. DESIGN: We performed a prospective cohort study. The Mealtime Habits Quality (MHQ) scale was used for assessing participants' MHQ; the outcomes of interest were gain ≥5 % of body weight, developing overweight/obesity and abdominal obesity, after 7 years of follow-up. In order to estimate the independent effect of MHQ on anthropometric indicators, generalized linear models were computed to obtain adjusted relative risks (95 % CI). SETTING: The state of Morelos, Mexico. SUBJECTS: Mexican adults (n 837) aged 18-70 years participating in a cohort study. RESULTS: Compared with participants classified in the higher MHQ category, individuals in the middle and lower MHQ groups had a 4·1 (2·5, 6·7) and 6·2 (3·9, 9·7) fold greater risk of gain ≥5 % of body weight, respectively; 6·6 (2·8, 15·5) and 8·6 (3·7, 19·8) fold greater risk of becoming overweight/obese, respectively; and 3·8 (2·0, 7·3) and 5·3 (2·8, 9·8) fold greater risk of developing abdominal obesity, respectively. CONCLUSIONS: This study provides evidence about the influence of a set of mealtime habits on obesity indicators, showing that greater adherence to unadvisable mealtime habits increases the risk of developing unhealthy anthropometric indicators. Since the meal is one of the most important sources of food intake, and consequently weight status, the MHQ scale can be a useful population tool to predict weight gain and obesity.

Health workers cohort study: methods and study design / Cohorte de trabajadores de la salud: métodos y diseño del estudio

Abstract: Objective: To examine different health outcomes that are associated with specific lifestyle and genetic factors. Materials and methods: From March 2004 to April 2006, a sample of employees from three different health and academic institutions, as well as their family members, were enrolled in the study after providing informed consent. At baseline and follow-up (2010-2013), participants completed a self-administered questionnaire, a physical examination, and provided blood samples. Results: A total of 10 729 participants aged 6 to 94 years were recruited at baseline. Of these, 70% were females, and 50% were from the Mexican Social Security Institute. Nearly 42% of the adults in the sample were overweight, while 20% were obese. Conclusion: Our study can offer new insights into disease mechanisms and prevention through the analysis of risk factor information in a large sample of Mexicans.

Resumen: Objetivo: Examinar diferentes desenlaces en salud y su asociación con factores genéticos y del estilo de vida. Material y métodos: De marzo de 2004 a abril de 2006, una muestra de empleados de tres diferentes instituciones de salud y académicas, así como miembros de sus familias, fueron enrolados en el estudio, previa firma de consentimiento informado. Durante la medición basal y el seguimiento (2010-2013) los participantes completaron un cuestionario autoaplicado, exámenes físicos y proporcionaron muestras sanguíneas. Resultados: Fueron incluidos participantes (10 729) de entre 6 y 94 años en la medición basal. De estos, 70% fueron mujeres y 50% del Instituto Mexicano del Seguro Social. Aproximadamente 42% de los adultos tuvieron sobrepeso y 20% obesidad. Conclusión: Este estudio puede ofrecer conocimientos sobre los mecanismos de la enfermedad a través del análisis de factores de riesgo en una muestra de mexicanos.

High Vitamin D Consumption Is Inversely Associated with Cardiovascular Disease Risk in an Urban Mexican Population.

BACKGROUND: Vitamin D deficiency is a major global public health problem. Recent epidemiological studies have assessed the relationship between vitamin D and multiple outcomes, including cardiovascular disease. However, this evidence is limited and inconclusive. Our purpose in this study was to evaluate the association between dietary vitamin D intake and cardiovascular disease risk in adult Mexican population. METHODS: We conducted a cross-sectional analysis with the baseline data from 6294 men and women aged 20-80 years participating in the Health Workers Cohort Study. Data on sociodemographic, lifestyle, and medical history factors were collected with a self-administered questionnaire. Dietary intake was evaluated by using a semi-quantitative food-frequency questionnaire. Cardiovascular disease risk was calculated using a recalibration of the Framingham heart disease prediction score. To evaluate the association between vitamin D intake and 10-year cardiovascular disease risk, odds ratios (OR) and 95% confidence intervals (95% CI) were calculated using multiple logistic regression analysis. RESULTS: A total of 6294 subjects (1820 men and 4474 women) with a mean age of 42 years, were included. Of these, subjects in the highest quintile of vitamin D intake presented lower levels of triglycerides 14.6 mg/dL (P for trend = 0.001); 2.0 cm less in waist circumference (P for trend = 0.001) and 0.8 points less in the Framingham cardiovascular disease risk score (P for trend = 0.002) compared with the subjects in the lower quintile of vitamin D intake. Additionally, participants in the highest quintile of vitamin D consumption were less likely to develop elevated 10-year cardiovascular disease risk, compared with those in the lowest quintile (OR = 0.51; 95%CI: 0.33, 0.77; P for trend = 0.007). CONCLUSION: Our data suggest that higher consumption of vitamin D is associated with a reduced risk of cardiovascular disease in Mexican population.

Mealtime habits and risk of developing the metabolic syndrome or insulin resistance among Mexican adults.

Meals are an important source of food intake, contributing to body weight and health status. Previous studies have examined the relationship between isolated mealtime behaviours and the metabolic syndrome (MetS). The aim of this study was to examine the influence over time of ten interrelated mealtime habits on the risk of developing the MetS and insulin resistance (IR) among Mexican adults. We conducted a prospective cohort study with a sample of 956 health workers. The Mealtime Habits Quality (MHQ) scale is based on four mealtime situations (availability of time to eat, distractions while eating, environmental and social context of eating, and familiar or cultural eating habits), which were used to assess the participants' MHQ at the baseline (2004-2006) and follow-up (2010-2012) evaluations. The MetS was assessed using criteria from the National Cholesterol Education Program Adult Treatment Panel III (NCEP-ATP III) and the International Diabetes Federation (IDF). IR was defined using the homoeostasis model assessment. Crude and adjusted relative risks were calculated to estimate the relationship between MHQ and the risk of developing the MetS or IR. Participants classified in the lower MHQ category had an 8·8 (95 % CI 3·1, 25) and 11·1 (95 % CI 3·4, 36·1) times greater risk of developing the MetS (using the NCEP-ATP III and IDF criteria, respectively), and an 11·2 times (95 % CI 3·9, 31·5) greater likelihood of developing IR, compared with those in the higher MHQ group. This prospective study reveals that individuals who engaged in more undesirable than recommended mealtime behaviours had a >10-fold risk of developing the MetS or IR.

Health workers cohort study: methods and study design.

OBJECTIVE:: To examine different health outcomes that are associated with specific lifestyle and genetic factors. MATERIALS AND METHODS:: From March 2004 to April 2006, a sample of employees from three different health and academic institutions, as well as their family members, were enrolled in the study after providing informed consent. At baseline and follow-up (2010-2013), participants completed a self-administered questionnaire, a physical examination, and provided blood samples. RESULTS:: A total of 10 729 participants aged 6 to 94 years were recruited at baseline. Of these, 70% were females, and 50% were from the Mexican Social Security Institute. Nearly 42% of the adults in the sample were overweight, while 20% were obese. CONCLUSION:: Our study can offer new insights into disease mechanisms and prevention through the analysis of risk factor information in a large sample of Mexicans.

Haplotypes in the CRP gene associated with increased BMI and levels of CRP in subjects with type 2 diabetes or obesity from Southwestern Mexico.

OBJECTIVE: We evaluated the association between four polymorphisms in the CRP gene with circulating levels of C-reactive protein (CRP), type 2 diabetes (T2D), obesity, and risk score of coronary heart disease. METHODS: We studied 402 individuals and classified them into four groups: healthy, obese, T2D obese, and T2D without obesity, from Guerrero, Southwestern Mexico. Blood levels of CRP, glucose, cholesterol, triglycerides, and leukocytes were measured. Genotyping was performed by PCR/RFLP, and the risk score for coronary heart disease was determined by the Framingham's methodology. RESULTS: The TT genotype of SNP rs1130864 was associated with increased body mass index and T2D patients with obesity. We found that the haplotype 2 (TGAG) was associated with increased levels of CRP (ß = 0.3; 95%CI: 0.1, 0.5; P = 0.005) and haplotype 7 (TGGG) with higher body mass index (BMI) (ß = 0.2; 95%CI: 0.1, 0.3; P < 0.001). The risk score for coronary heart disease was associated with increased levels of CRP, but not with any polymorphism or haplotype. CONCLUSIONS: The association between the TT genotype of SNP rs1130864 with obesity and the haplotype 7 with BMI may explain how obesity and genetic predisposition increase the risk of diseases such as T2D in the population of Southwestern Mexico.

Diseños de investigación en epidemiología genética / Genetic epidemiology research designs

Se describen los distintivos de los diseños de investigación epidemiológica que son utilizados con mayor frecuencia en los estudios de asociación genética. Los estudios de casos y controles proporcionan un método eficiente para evaluar asociaciones entre genes candidatos y enfermedad. Los estudios de cohorte, por su parte, si bien aportan un mayor grado de causalidad, no son eficientes para la exploración inicial en la identificación de las asociaciones gen-enfermedad. Los estudios transversales son menos costosos, requieren períodos de tiempo más cortos y son de utilidad para estimar la prevalencia de enfermedades, de factores de riesgo o de variantes genéticas. Los estudios basados en familias han sido exitosos para encontrar alelos que confieren mayor riesgo para el desarrollo de enfermedades de transmisión mendeliana.

This article describes the features of the epidemiologic research designs most commonly used in genetic association studies. Case-control studies are efficient in evaluating associations between candidate genes and disease. Cohort studies, in contrast, yield a greater degree of causality but are not efficient for the initial exploration to identify gene-disease associations. Cross-sectional studies are less expensive, require less time, and are useful for estimating the prevalence of diseases, risk factors, and genetic variants. Family-based studies have been successful in finding alleles that confer greater risk for developing Mendelian inheritance disorders.

[Case crossover studies: a conceptual and methodological approach]. / Estudio epidemiológico de casos y autocontroles: una aproximación conceptual y metodológica.

Case crossover studies are considered as a variant of case control studies, and they have been included in the scientific literature since approximately eighteen years ago. They have also been used in epidemiological research on acute or intermittent exposures that may lead to a number of events including heart attack or cardiac arrest, injuries, asthma, etc. Application of this particular study design requires defining concepts such as: triggers, induction time, case period and control period. Its use is limited in studies on chronic exposures. On the other hand, this type of design may reduce selection and misclassification bias, confounding, and overmatching. Another advantage is that it requires a small sample size because the same case can be used as its own control in one or several periods. Nevertheless, sample size calculation must be assessed as a matched case-control study. This is a type of study in which theoretical principles are accomplished in a sui generis manner.

Estudio epidemiológico de casos y autocontroles: una aproximación conceptual y metodológica / Case crossover studies: a conceptual and methodological approach

Los estudios de casos y autocontroles se clasifican como una variante de los estudios de casos y controles. Se han mencionado en la literatura científica desde hace aproximadamente 18 años, y son empleados en investigaciones epidemiológicas con exposiciones agudas o transitorias que pueden generar un evento en salud (infarto agudo del miocardio, asma, lesiones, enfermedades infectocontagiosas, entre otras). Para su manejo se requiere definir conceptos tales como disparadores, tiempo de inducción, periodo de caso, periodo de control. Su uso es limitado en la evaluación de exposiciones crónicas o no intermitentes. Por otro lado, este diseño reduce sesgos de selección, de información, de confusión y el sobrepareamiento. Una de sus ventajas es que requieren menor tamaño de muestra que un estudio clásico de casos y controles, donde los periodos de control se pueden obtener del mismo sujeto, sin la necesidad de entrevistar a otro tipo de controles. No obstante, para el cálculo del tamaño de la muestra se debe tener encuenta el enfoque de diseños pareados. Éste es un diseño donde los principios teóricos de homogeneidad, simultaneidad y representatividad se cumplen de manera singular.

Case crossover studies are considered as a variant of case control studies, and they have been included in the scientific literature since approximately eighteen years ago. They have also been used in epidemiological research on acute or intermittent exposures that may lead to a number of events including heart attack or cardiac arrest, injuries, asthma, etc. Application of this particular study design requires defining concepts such as: triggers, induction time, case period and control period. Its use is limited in studies on chronic exposures. On the other hand, this type of design may reduce selection and misclassification bias, confounding, and overmatching. Another advantage is that it requires a small sample size because the same case can be used as its own control in one or several periods. Nevertheless, sample size calculation must be assessed as a matched case-control study. This is a type of study in which theoretical principles are accomplished in a sui generis manner.

Body mass index associated with elevated blood pressure in Mexican school-aged adolescents.

OBJECTIVE: To evaluate the relationship between blood pressure and body mass index among adolescents. METHODS: A 14-month period cross-sectional study was carried out among 2387 adolescents attending public schools in the state of Morelos, Mexico between 2005 and 2007. We measured blood pressure during four visits, obtaining elevated blood pressure prevalence according to the guidelines for children and adolescents of the United States National Educational Program on High Blood Pressure (at least three visits needed to assess elevated blood pressure on the basis of 95th percentile specific for gender, age and height). We used specific body mass index percentiles for age and gender. We employed multiple linear and Cox proportional hazards models to identify factors related to elevated blood pressure. RESULTS: The overall prevalence of elevated blood pressure was 3.9%. Multiple linear models showed that overweight subjects had systolic and diastolic blood pressures that were 5.1 and 2.5 mmHg higher, respectively, compared with adolescents with a normal body mass index, while obese subjects had 11.3 and 6.2 mmHg higher levels, respectively. Cox proportional hazards models indicated high risk of elevated blood pressure among overweight (RR, 3.6; 95%CI, 1.5-8.5) and obese subjects (RR, 14.2; 95%CI, 7.2-27.75) compared with adolescents with a normal body mass index. CONCLUSION: Our results suggest that a higher body mass index is associated with elevated systolic and diastolic blood pressure levels, indicating the importance of incorporating strategies for ongoing screening and for promoting educational programs on healthy lifestyles to prevent hypertension in adolescents.

[The alternative medicine used as complementary in patients positive for HIV]. / Uso de terapia alternativa/complementaria en pacientes seropositivos a VIH.

OBJECTIVE: To evaluate the use of complementary alternative medicine (CAM) in patients infected with the human immunodeficiency virus (HIV), and to identify the type and factors associated to its use. METHODS: Cross-sectional study made in HIV clinics of three majors institutions from Morelos State, Mexico; the sample was 293 subjects; a specific questionnaire looking for demographic information and CAM use was applied. RESULTS: The use of CAM was 73.4%; 71% informed to the physician of their use. 51% of the patients reported using nutritional complements, 29.7% herbal products and 19% used physical agents like exercise, Chinese medicine, and therapy by contact. A total of 96.6 % of the users reported some perception of benefit with its use. The patients with low income, IMSS beneficiaries and on antirretroviral treatment were the greatest CAM users. CONCLUSIONS: CAM use is a common practice among HIV (+) patients. The multivitamins and herbal products were the most used. The majority was prescribed by health personnel and the users showed some benefit. Other longitudinal studies are required to establish the CAM impact on the disease evolution and the quality of life of HIV (+) patients.