The impact of altitude on mortality from tuberculosis and pneumonia.

OBJECTIVE: To examine the association between altitude and mortality from tuberculosis (TB) and pneumonia-influenza in Mexico. DESIGN: We analysed specific causes of death in Mexico according to death certificates for the period 1993-1997, totalling over 2,700,000 deaths and including nearly 23,000 attributed to TB and 115,000 to pneumonia and influenza. Thirty population subgroups were formed based on altitude of residence (six categories) and level of poverty (five categories). The effect of altitude on mortality was estimated through Poisson regression models, with adjustment for age, gender and socioeconomic status. RESULTS: Adjusted death rates for TB decreased with altitude and increased for pneumonia-influenza. Compared to people living below 500 m above sea level, those living between 2000 and 2499 m had a 58% mortality rate for TB and a three-fold increase in mortality due to pneumonia-influenza, despite adjustment for poverty, age and gender. CONCLUSION: The mortality rate for TB based on death certificates decreases with altitude of residence, whereas the opposite is observed for pneumonia and influenza.

[Epidemiologic panorama of cancer mortality in the Mexican Institute of Social Security: 1991-1995]. / Panorama epidemiológico de la mortalidad por cáncer en el Instituto Mexicano del Seguro Social: 1991-1995.

OBJECTIVE: This paper describes the global cancer mortality and the specific mortality patterns for the main neoplasms among adult members of the Mexican Institute of Social Security (IMSS). MATERIAL AND METHODS: Using official death certificates and information about the population of the IMSS members during 1991-1995, national and regional annual global cancer mortality as well as specific mortality rates for the 10 most important malignant neoplasms by sex were estimated among people older than 20 years of age. The trends for these neoplasms during the study period were estimated by means of Poisson regression. The rate differences in specific cancer mortality by region and sex, for the two major neoplasms, were calculated subtracting specific regional rates from the respective national rate in 1995. RESULTS: The global mortality rate for cancer among men increased from 76.2 in 1991 to 94.8 x 100000 IMSS' members in 1995; and among women from 85.6 to 105.8 x 100000 IMSS' members, representing an increment of 24.4 and 24% men and women, respectively, during the study period. Among men, neoplasm of kidney, leukemia, pancreas, prostate and lung showed the major increment; among women, neoplasm of colon, breast, pancreas, leukemia and liver showed the most significant increment. CONCLUSIONS: In the IMSS it is necessary the integration of a population based cancer registry. The registry will play a main role in disease surveillance and control; will give basic information over incidence and temporal variation, and could be the main source of information for epidemiologic research, as well as planning and evaluation of the quality of medical attention services such as prevention and early diagnosis and treatment.

Bias from nondifferential misclassification in case-control studies with three exposure levels.

In case-control studies with three exposure levels where disease risk is associated with exposure, the direction of bias in the odds ratios (ORs) from nondifferential misclassification depends on the risk level, misclassification rates, and exposure distributions. To extend these generalizations, we present a graphical analysis of bias from nondifferential misclassification assuming linear and nonlinear monotonic increasing exposure-risk patterns. In both middle and upper exposure levels, bias is usually toward the null, increasing in magnitude as the misclassification rates increase and as the skewness of the exposure distribution increases. In the middle exposure level, bias away from the null may occur when the misclassification rate is low in the reference level and moderate to high in the upper exposure level, and risk increases with exposure. Bias away from the null does not occur in the upper exposure level. In both excess risk levels, crossover bias (that is, a reversal of the OR) may occur when exposure classification is worse than chance. The magnitude of bias away from the null is constrained by the unbiased OR of the upper exposure level, whereas that of crossover bias is constrained by the inverse of the unbiased OR of the upper exposure level.

[Strategy for controlling poliomyelitis in Mexico: greater vaccination coverage of children less than 1 year of age]. / Una estrategia para el control de la poliomielitis en México: mayor cobertura de vacunación en menores de un año.

In spite of the widespread use of oral poliovirus vaccine, some countries have not achieved an optimal control of poliomyelitis. According to Sabin, this fact is due to a lack of immunization coverage of children under one year of age. In this study, the relationship between the general morbidity rate for polio and vaccination coverage of children under one year of age, in people protected by the Mexican Institute of Social Security, is analyzed. There is a negative correlation between these two variables: the lesser the coverage, the greater the rates. There is also a correlation between the rate of polio and the rate of polio for the year prior to each of the years of the study period. In a multiple regression model, both the coverage and the rate for the previous year were significantly correlated with the rate of polio. In order to get an optimum control of this disease, it is advantageous to consider that it is not enough to increase the coverage but that this coverage must be opportune, i.e., in the first year of life.

[Evaluation of epidemiological articles published in 2 journals in the area of public health]. / Una evaluación de los artículos epidemiológicos publicados en dos revistas del área de la salud pública.

The main aim of this study was to assess the quality and quantity of the Mexican epidemiologic production published in two journals: Salud Pública de México (SPM) and Boletín de la Oficina Sanitaria Panamericana (BOSP). A previously accepted criterion was used to qualify a paper as an epidemiologic work. The period of study was eleven years (1975-1985) with 89 classified paper as "epidemiologic reports" (36 of BOSP and 53 of SPM). The variables included: original or revision's report; epidemiologic design; measures employed (frequency, association or potential impact); condition (contagious diseases, chronic-degenerative diseases or physiologic status); use of prevalent cases, incident cases or deaths; internal and external validity; bias' recognition; and number of references. Among the results that stand out are the proportion of cross-sectional designs (51.75), the weight for communicable diseases (36%), the detection of potential bias (65.7%) and the reports without references (30%). The discussion is centered in the main implications of these results when they are used to make decisions in the planning, operation and assessment of health services and in the generation of new epidemiologic knowledge.

[Differential mortality by sex. Causes and behavior of respiratory and gastroenteric infections in Mexico]. / Mortalidad diferencial por sexo. Causas y comportamiento de las infecciones respiratorias y gastroenterales en México.

The differential in mortality by sex has not been broadly studied in Mexico. In this work mortality by sex in under one year old children and infants by federal entity for the main infectious diseases during 1980-1982 was analyzed. The results showed that the rate of mortality by sex (RMS) for under one year old children was higher than one, which means that there is a male over-mortality for that group of age. In the one to four year old children group, there were three entities that showed over-mortality among women. The analysis of the proportional mortality revealed that 40 to 50 percent of deaths in under one year old children were due to gastroenteral and respiratory infections. The probable causes of the male over-mortality observed and the need to determine the regional patterns of mortality are also discussed.