Changes in the epidemiological profile of SARS-CoV-2-positive individuals in Mexico across pandemic waves as an explanation of fatality reduction: a retrospective observational study.

OBJECTIVES: We aim to quantify shifts in hospitalisation and mortality and how those were related to the first three phases of the epidemic and individuals' demographics and health profile among those with a positive test for SARS-CoV-2 treated at the Mexican Social Security Institute's facilities from March 2020 to October 2021. DESIGN: Retrospective observational study using interrupted time series analysis to identify changes in hospitalisation rate and case fatality rate (CFR) by epidemic wave. SETTING: Data from the Mexican Institute of Social Security's (IMSS) Online Influenza Epidemiological Surveillance System (SINOLAVE) that include all individuals that sought care at IMSS facilities all over Mexico. PARTICIPANTS: All individuals included in the SINOLAVE with a positive PCR or rapid test for SARS-CoV-2. PRIMARY AND SECONDARY OUTCOME MEASURES: Monthly test positivity rates, hospitalisation rates, CFRs and prevalence of relevant comorbidities by age group. RESULTS: From March 2020 to October 2021, the CFR declined between 1% and 3.5%; the declines were significant for those 0-9, 20-29, 30-39, 40-49 and 70 and older. The decline was steep during the first wave and was less steep or was temporarily reversed at the beginning of the second and third waves (changes in the trend of about 0.3% and 3.8%, and between 0.7% and 3.8%, respectively, for some age groups), but then continued to the end of the analytical period. Prevalence of diabetes, hypertension and obesity among patients testing positive also declined-two for most age groups (reductions of up to 10 percentage points for diabetes, 12 percentage points for hypertension and 19 percentage points for obesity). CONCLUSION: Data suggest that the decrease in COVID-19 fatality rate is at least partially explained by a change in the profile of those contracting the disease, that is, a falling proportion of individuals with comorbidities across all age groups.

Evolution of differences in clinical presentation across epidemic waves among patients with COVID-like-symptoms who received care at the Mexican Social Security Institute.

Background: Timely monitoring of SARS-CoV-2 variants is crucial to effectively managing both prevention and treatment efforts. In this paper, we aim to describe demographic and clinical patterns of individuals with COVID-19-like symptoms during the first three epidemic waves in Mexico to identify changes in those patterns that may reflect differences determined by virus variants. Methods: We conducted a descriptive analysis of a large database containing records for all individuals who sought care at the Mexican Social Security Institute (IMSS) due to COVID-19-like symptoms from March 2020 to October 2021 (4.48 million records). We described the clinical and demographic profile of individuals tested (3.38 million, 32% with PCR and 68% with rapid test) by test result (positives and negatives) and untested, and among those tested, and the changes in those profiles across the first three epidemic waves. Results: Individuals with COVID-19-like symptoms were older in the first wave and younger in the third one (the mean age for those positive was 46.6 in the first wave and 36.1 in the third wave; for negatives and not-tested, the mean age was 41 and 38.5 in the first wave and 34.3 and 33.5 in the third wave). As the pandemic progressed, an increasing number of individuals sought care for suspected COVID-19. The positivity rate decreased over time but remained well over the recommended 5%. The pattern of presenting symptoms changed over time, with some of those symptoms decreasing over time (dyspnea 40.6 to 14.0%, cough 80.4 to 76.2%, fever 77.5 to 65.2%, headache 80.3 to 78.5%), and some increasing (odynophagia 48.7 to 58.5%, rhinorrhea 28.6 to 47.5%, anosmia 11.8 to 23.2%, dysgeusia 11.2 to 23.2%). Conclusion: During epidemic surges, the general consensus was that any individual presenting with respiratory symptoms was a suspected COVID-19 case. However, symptoms and signs are dynamic, with clinical patterns changing not only with the evolution of the virus but also with demographic changes in the affected population. A better understanding of these changing patterns is needed to improve preparedness for future surges and pandemics.

How predictive of SARS-CoV-2 infection are clinical characteristics at presentation among individuals with COVID-like symptoms treated at the Mexican Institute of Social Security.

BACKGROUND: The COVID-19 pandemic has progressed rapidly, with the emergence of new virus variants that pose challenges in treating infected individuals. In Mexico, four epidemic waves have been recorded with varying disease severity. To understand the heterogeneity in clinical presentation over time and the sensitivity and specificity of signs and symptoms in identifying COVID-19 cases, an analysis of the changes in the clinical presentation of the disease was conducted. AIM: To analyze the changes in the clinical presentation of COVID-19 among 3.38 million individuals tested for SARS-CoV-2 at the Mexican Social Security Institute (IMSS) from March 2020 to October 2021 and evaluate the predictivity of signs and symptoms in identifying COVID-19 cases. METHODS: A retrospective analysis of clinical presentation patterns of COVID-19 among individuals treated at IMSS was performed, contrasting the signs and symptoms among SARS-CoV-2-positive individuals with those who tested negative for the virus but had respiratory infection symptoms. The sensitivity and specificity of each sign and symptom in identifying SARS-CoV-2 infection were estimated. RESULTS: The set of signs and symptoms reported for COVID-19-suspected patients treated at IMSS were not highly specific for SARS-CoV-2 positivity. The signs and symptoms exhibited variability based on age and epidemic wave. The area under the receiver operating characteristic (ROC) curve was 0.62 when grouping the five main symptoms (headache, dyspnea, fever, arthralgia, and cough). Most of the individual symptoms had ROC values close to 0.5 (16 out of 22 between 0.48 and 0.52), indicating non-specificity. CONCLUSIONS: The results highlight the difficulty in making a clinical diagnosis of COVID-19 due to the lack of specificity of signs and symptoms. The variability of clinical presentation over time and among age groups highlights the need for further research to differentiate whether the changes are due to changes in the virus, who is becoming infected, or the population, particularly with respect to prior infection and vaccination status.

Improvement of child survival in Mexico: the diagonal approach.

Public health interventions aimed at children in Mexico have placed the country among the seven countries on track to achieve the goal of child mortality reduction by 2015. We analysed census data, mortality registries, the nominal registry of children, national nutrition surveys, and explored temporal association and biological plausibility to explain the reduction of child, infant, and neonatal mortality rates. During the past 25 years, child mortality rates declined from 64 to 23 per 1000 livebirths. A dramatic decline in diarrhoea mortality rates was recorded. Polio, diphtheria, and measles were eliminated. Nutritional status of children improved significantly for wasting, stunting, and underweight. A selection of highly cost-effective interventions bridging clinics and homes, what we called the diagonal approach, were central to this progress. Although a causal link to the reduction of child mortality was not possible to establish, we saw evidence of temporal association and biological plausibility to the high level of coverage of public health interventions, as well as significant association to the investments in women education, social protection, water, and sanitation. Leadership and continuity of public health policies, along with investments on institutions and human resources strengthening, were also among the reasons for these achievements.

Design and validation of a population-based definition of the metabolic syndrome.

OBJECTIVE: The National Cholesterol Education Program (NCEP) definition of the metabolic syndrome was modified to be described as a continuous variable and adapted to the characteristics of a Hispanic population. RESEARCH DESIGN AND METHODS: Age/sex population percentiles for every component of the NCEP criteria were included in this approach using population-based data from a Mexican nationwide survey (2,158 subjects). One point was given per decile for every component. The total number of points accumulated was used to classify subjects. The predictive power for incident diabetes was evaluated using the 7-year follow-up results of the Mexico City Diabetes Study. RESULTS: Our population-based method had a significantly better prognostic power compared with the original and the updated NCEP definitions (area under the receiver operating characteristic curve 0.746 vs. 0.697 and 0.723, respectively, P < 0.05). Using individuals with /=39 points) (12.71 [95% CI 5.67-28.49]) compared with that calculated for the original (9.52 [4.69-19.31]) and the updated (11.14 [5.33-23.30]) NCEP criteria. The major advantage of our approach is the detection of subjects at the extremes of the range of diabetes risk and the ability to estimate this risk as a continuum. CONCLUSIONS: Our method adapts the NCEP criteria to the characteristics of a Hispanic population. It improves the predictive power of the NCEP criteria for future diabetes.

The Past, Present, and Future of Mexico's National Bioethics Commission.

The establishment of Mexico's National Bioethics Commission (Comisión Nacional de Bioética), in 1992, was conceived within the context of a global movement aimed at raising awareness of the ethical implications of technological and scientific development, especially in biomedicine. In 2005, a new decree put the commission under the scope of the Secretariat of Health and granted it technical and operational autonomy, allowing it to become a regulatory agency aimed at promoting a culture of bioethics, encouraging reflection on human health, and developing guidelines for health care, research, and education, through a global, secular, and democratic perspective. The commission became the leading actor in the strategy for institutionalizing bioethics in Mexico after reforms to the country's General Health Act in 2011, which required that public, social assistance, or private health care facilities establish a hospital bioethics committee to address bioethical dilemmas or issues and, when relevant, a research ethics committee to address research with human subjects. This assignment has shifted the focus of the activities and goals of the National Bioethics Commission toward establishing these committees in line with current regulations and developing mechanisms to ensure that they operate with the highest standards of ethical conduct, performance, and accountability.

Obesity among children residing in Mexico City and its impact on lung function: a comparison with Mexican-Americans.

BACKGROUND: The objective of the study was to describe the prevalence of obesity among Mexican children and its impact on ventilatory lung function. METHODS: We studied cross-sectionally 6784 students between 8 and 20 years of age attending schools located <2 km away from ten air pollution monitors located throughout metropolitan Mexico City. The comparison group was made up of 1924 Mexican-Americans of the same age, studied during the NHANES-III examination, which included information on spirometry and body mass index (BMI). RESULTS: Of all our subjects, 9.7% had a BMI >95(th) percentile of CDC growth charts (compared to 15.1% in Mexican-Americans) and 6.6% fulfilled the obesity criteria of the International Obesity Task Force (vs. 12.2%). Obesity was related to male gender, asthma and passive smoking. At the same height and gender, lung function was higher in Mexicans than in Mexican-Americans, perhaps due to altitude. In children 8-11 years of age, lung function increased in heavier subjects but, in older children and youths, function reached a plateau and decreased among children with highest BMI (inverted U pattern, seen in adults). CONCLUSIONS: Obesity is higher in Mexican-American children and youths than in Mexicans. Spirometric function is affected adversely by obesity, especially in young people.

Epidemiology of type 2 diabetes in Mexico.

The epidemiology of diabetes in Mexico is reviewed. In less than four decades, diabetes has become the main health problem in Mexico. It is the principal cause of death in women and the second among men since the year 2000. It is the primary cause of premature retirement, blindness, and kidney failure. By the year 2025, close to 11.7 million Mexicans are expected to be diagnosed with diabetes. In the year 2000, diabetes was the 11th most frequent cause of hospitalization but the second most common cause of hospital mortality. The number of cases reported in children has also increased since 1995. The results of population-based, nationwide surveys have detected a 25% increment over a 7-year period. Fourteen percent of people with diabetes are <40 years of age, and a large proportion of patients have other conditions that determine the appearance of macrovascular complications and kidney failure. In addition, many cases do not reach treatment goals. In conclusion, the growing number of cases and the significant health burden imposed on affected subjects makes diabetes a disease that needs to be prevented. Well-planned strategies are urgently needed to modify the lifestyle of the population and to increase their physical activity. In addition, an enormous effort will be required to educate the population and physicians to improve the diagnosis and treatment of patients with diabetes.

The metabolic syndrome: a concept hard to define.

The metabolic syndrome integrates, in a single diagnosis, the manifestations of insulin resistance that may lead to increased cardiovascular morbidity and precedes type 2 diabetes. Here we discuss the strengths and limitations of the definitions of the metabolic syndrome and the epidemiology of the syndrome including information from non-Caucasian populations. The definitions proposed by the World Health Organization (WHO) and the National Cholesterol Education Program (NCEP) are the most frequently used. The relative risk of having long-term complications is greater for the WHO definition; this is explained by the inclusion of the insulin resistance criteria. The cut-off points used in these definitions should be, but are not, adjusted for ethnicity; as a result, in non-Caucasian subjects, there is lack of agreement among these criteria. In a Mexican population-based survey the prevalence was 13.61% using the WHO definition and 26.6% using the NCEP-III criteria. Cases identified by the WHO criteria had a more severe form of the disease. We propose that the metabolic syndrome should be viewed as a progressive long-term process that leads to major complications. Its definition should reflect the continuous nature of the disease; the categorical approach of the current criteria oversimplifies the complexity of the syndrome. The threshold for defining abnormality should be based on the associated risk of the identified phenotype. Refinement of the definition of both affected and nonaffected subjects is required. The available definitions include, in each of these categories, heterogeneous groups with a broad range of risk of future complications.

Applicability of the National Cholesterol Education Program III (NCEP-III) guidelines for treatment of dyslipidemia in a non-Caucasian population: a Mexican nation-wide survey.

We assessed the impact of the NCEP-III recommendations in a population-based, nation-wide Mexican survey. Information was obtained from 15,607 subjects aged 20 to 69 years. In this report, only samples obtained after a 9 to 12 hours fast are included (2,201 cases). A cardiovascular risk equivalent was found in 10.5% and > or = 2 risk factors were present in 41.7% of the population. In 10% of cases, the LDL-C concentration was high enough to be an indication for a lipid-lowering drug (> 160 mg/dL), independent of the presence of risk factors. A quarter of the population was eligible for some form of treatment (lifestyle modifications in 15.9%, drug therapy in an additional 11.7%). Among cases with > or = 2 risk factors, a small percentage (1.8%) were identified as having a 10 year-risk > 20% and 86.3% were considered as having a 10 year-risk < 10%. The majority of the metabolic syndrome cases (84%) were identified as low-risk subjects. As a result, only 17.6% of them qualified for drug-based LDL-C lowering. Our data helps to estimate of the magnitude of the burden imposed on the Mexican health system, of lowering LDL-C for cardiovascular prevention. If we apply our results to the 2,000 Mexican population census more than 5.8 million cases nationwide may require LDL lowering drug therapy following the NCEP-III criteria.

Prevalence and characteristics of early-onset type 2 diabetes in Mexico.

OBJECTIVE: To investigate the prevalence and characteristics of patients with type 2 diabetes diagnosed before the age of 40 years (early-onset disease) in a nationwide, population-based study. METHODS: Using a multistage sampling procedure, we enrolled a representative sample of Mexican urban adults aged 20 to 69 years. Weight, height, blood pressure, and plasma levels of glucose, insulin, and other metabolic parameters were measured in all subjects. RESULTS: We identified 993 subjects with type 2 diabetes, including 143 subjects aged 20 to 39 years (14% of those with diabetes). Subjects with early-onset diabetes had a greater prevalence of obesity and higher plasma insulin and lipid levels than did age-matched controls, and a greater prevalence of high-density lipoprotein cholesterol levels <35 mg/dL and severe hypertriglyceridemia than did older subjects with diabetes. Those (n = 32) with a normal body mass index (20 to 25 kg/m(2)) tended to have insulin deficiency as the main abnormality, whereas the "metabolic syndrome" characterized the remaining 111 subjects with early-onset diabetes. CONCLUSION: Most patients with early-onset type 2 diabetes in Mexico are obese or overweight, suggesting that obesity treatment and prevention programs may be effective in reducing the prevalence of this disease.

Spirometric variability in a longitudinal study of school-age children.

OBJECTIVES: To describe spirometric reproducibility in a longitudinal study of students from Mexico City, and also the frequency of subjects fulfilling quality criteria proposed for children. SUBJECTS AND METHODS: Three thousand three hundred forty-seven participants from the third through sixth grades of elementary school were recruited to perform biannual spirometry, yielding a maximum of seven evaluations and a total of 15,563 tests. Standard recommendations of the American Thoracic Society (ATS) were followed, using dry rolling-seal volume spirometers. RESULTS: During their first spirometric test, > 95% of the subjects fulfilled each of the quality criteria proposed by ATS for adults, though not all of them did so simultaneously. For example, only 72.4% obtained three acceptable maneuvers, reproducibility for FEV(1) and FVC to < 200 mL, and a small back-extrapolated volume that increased to 92.3% by the second test. Between phase 1 and phase 7 of the study, spirometry quality increased significantly, as a result of subject and technician training. Intratest and intertest (with a 6-month difference) spirometric variability was less in boys than in girls. Intratest variability was also lower in younger and taller subjects. Technicians contributed significantly to intratest and intertest variability, the latter decreasing if the same technician performed both evaluations. CONCLUSION: Children > 7 years old can fulfill ATS criteria of quality after the first spirometric evaluation. To maintain quality of spirometric tests in longitudinal studies of children, a strict control is required, especially of technician performance.

Nutrition transition in Mexico and in other Latin American countries.

Mexico and other Latin American countries are currently undergoing important demographic, epidemiologic and nutrition transitions. Noncommunicable chronic diseases such as obesity, type 2 diabetes mellitus, and high blood pressure are becoming public health problems as the population experiences an important reduction in physical activity and an increase in energy-dense diets. In contrast, the prevalence of undernutrition is declining in most countries, although several decades will be needed before the prevalence drops to acceptable values. The objective of this article is to discuss the characteristics of the nutrition transition with emphasis in data from Mexico, Brazil, and Chile.

Apolipoprotein B and A-I distribution in Mexican urban adults: results of a nationwide survey.

The apolipoprotein (apo) B and A-I distribution found in a survey performed in 417 Mexican cities is described. Information was obtained from 15,607 subjects aged 20 to 69 years. In this report, only samples obtained after a 9- to 12-hour fast were included (1,674 cases, 652 men and 1,022 women). The population is representative of the Mexican urban adults. Mean lipid concentrations were: cholesterol,182.7 mg/dL; triglycerides, 213 mg/dL; high-density lipoprotein (HDL) cholesterol, 38.3 mg/dL; and low-density lipoprotein (LDL) cholesterol, 116 mg/dL. The mean concentration of apo B was 77.8 +/- 25.9 mg/dL and 71 +/- 22.8 in men and women, respectively. A continuous increase of apo B was observed as subjects got older. A tendency to decrease after age 60 was observed in men, but not in women. The body mass index (BMI) is a major determinant for the apo B concentrations. The 90th percentile of the apo B concentration identifies a similar proportion of abnormal subjects than the LDL cholesterol concentration of 160 mg/dL. The 120 mg/dL concentration, upper normal limit level used in other populations, identified as abnormal only 3.8% of the cases. Regardless of the lipid abnormality, an apo B above the 90th percentile was associated with higher levels of glucose, cholesterol, triglycerides, and non-HDL cholesterol, despite a similar age and BMI. The overall mean concentration of apo A-I was 122.3 +/- 31 mg/dL and 129 +/- 34 in men and women, respectively. In conclusion, our data show that the apo B and apo A-I concentrations in Mexican urban adults are lower compared with the levels reported in other ethnic groups. Previously used reference ranges are not useful in the population report herein. These observations strengthen the need for obtaining data in population-based studies worldwide.

High prevalence of metabolic syndrome in Mexico.

BACKGROUND: Our objective was to describe the prevalence of the metabolic syndrome using World Health Organization (WHO) and National Cholesterol Education Program (NCEP-III) definitions in a population-based survey. METHODS: We performed an analysis of data from a Mexican nationwide, population-based study. The population was composed of 2,158 men and women aged 20-69 years sampled after a 9-12 h fasting period. Prevalence of the metabolic syndrome as defined by the NCEP-III definition and WHO criteria was estimated and case characteristics were assessed. RESULTS: Age-adjusted prevalence was 13.61% for WHO criteria and 26.6% for the NCEP-III definition. Prevalence was 9.2 and 21.4%, respectively, in subjects without diabetes. Thirty five percent of affected cases were <40 years of age. In addition to criteria used for diagnosis, ca. 90% were either overweight or obese. In cases detected using WHO criteria, antihypertensive treatment or blood pressure reading >140/90 was found in 61.8%. The proportion of subjects who qualified for hypolipemiant treatment was lower: lifestyle modifications were needed in 42.1% and drug therapy was required in 18.9%. The same trends were found for cases detected using the NCEP definition. CONCLUSIONS: Prevalence of the metabolic syndrome in Mexico is high. A large proportion of affected cases qualify for preventive actions for complications of the metabolic syndrome (i.e., weight loss, antihypertensive or hypolipemiant treatment). These results provide data for planning therapeutic programs for Mexican patients with the metabolic syndrome.

Spirometric function in children of Mexico City compared to Mexican-American children.

We set out to describe the pattern of lung function growth in Mexican students from 8-20 years of age, using internationally accepted equipment and methodology, and to compare it to values reported for Mexican-American children. Out of a total of 6,803 students from primary school to high school studied cross-sectionally in the Mexico City metropolitan area, we selected 4,009 asymptomatic, nonobese, nonsmoker subjects to generate spirometric prediction equations. We describe regression equations for the main spirometric variables (log transformed) based on age, height, and weight, and separated for males and females. Spirometric function in the population studied was above that predicted for European (Quanjer et al. [1987] Pediatr Pulmonol 19:135-142) or Mexican-American children, for the same age, height, and gender. On average, forced expiratory volume in 1 sec (FEV(1)) in Mexican children was 9.5% above that of Europeans (Quanjer et al. [1987] Pediatr Pulmonol 19:135-142), 14% and 5% above Hispanics reported by (Coultas et al. [1988] Am Rev Respir Dis 138:1386-1392) and (Hsu et al. [1979] J Pediatr 95:14-23), respectively, and 5% above Mexican-Americans from the third National Health and Nutrition Examination Survey study. Similarly, FVC was 8%, 14%, 8%, and 5.6% above the figures predicted by the same authors. The largest errors of prediction of foreign equations occurred in extremely tall or short subjects, and therefore a single proportional adjustment is unfeasible.

[Characteristics of mixed hyperlipidemia cases in a population-based study: results from the Mexican National Survey of Chronic Diseases]. / Características de los casos con dislipidemias mixtas en un estudio de población: resultados de la Encuesta Nacional de Enfermedades Crónicas.

OBJECTIVE: To describe the characteristics of mixed hyperlipidemia cases, using data derived from the Encuesta Nacional de Enfermedades Crónicas (Mexican National Survey of Chronic Diseases, ENEC). MATERIAL AND METHODS: The ENEC was conducted in 1993, in 417 Mexican cities. Blood measurements of lipids, glucose, and insulin were obtained from 2206 cases. Differences between dyslipidemia patients and non cases were obtained using analysis of variance or the chi-squared test. RESULTS: Mixed hyperlipidemia was diagnosed in 282 subjects (12.8%). Cases were 42.7+/-12.6 years old. Fifty six percent were males and 46.4% had HDL cholesterol levels < 0.9 mmol/l. Other cardiovascular risk factors were also present. The prevalence of mixed hyperlipidemia was high even among young adults. A logistic regression model showed that obesity, age, male gender, residence in some regions of Mexico, diabetes, arterial hypertension, and fasting insulin levels >21 mU/ml, were factors associated with mixed hyperlipidemia. CONCLUSIONS: Mixed hyperlipidemia is a very common condition in Mexican adults. It is more common in males older than 30 years, with additional cardiovascular risk factors. Study findings suggest that the metabolic syndrome plays a role in the pathogenesis of this disorder.

[The metabolic syndrome: a concept in evolution]. / El síndrome metabólico: un concepto en evolución.

The concept metabolic syndrome intends to incorporate in a single disorder all biologic consequences of insulin resistance and associated conditions. The objective of this paper was to discuss strengths and limitations of current definitions of the metabolic syndrome, its epidemiology, and its association with non-alcoholic steatohepatitis (NASH). Definitions proposed by the World Health Organization (WHO) and the National Cholesterol Education Program (NCEP) are specific but possess low sensitivity for detecting insulin resistance. Cut-off points used in these definitions should be "but are not" adjusted for ethnicity; as a result, in non-Caucasian subjects there is lack of agreement among these. For example, in a Mexican population-based survey prevalence was 13.61% using the WHO definition and 26.6% employing NCEP-III criteria. Cases identified with WHO criteria have a more severe form of the disease. NASH is the most common cause of abnormal levels of serum aminotransferases. It shares some aspects of its pathophysiology with the metabolic syndrome and its prevalence is higher among cases with metabolic syndrome compared to with general population. NASH appears to be the hepatic manifestation of the metabolic syndrome.