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A Tobías Garcés

Publications and source records attributed to A Tobías Garcés.

4 recordsLinked to original sources
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[Application of tobit regression models in modelling censored epidemiological variables].

Many variables in epidemiological studies are continuous measures obtained by means of measurement equipments with detection limits, generating censored distributions. The censorship, opposite to the trucation, takes place for a defect of the data of the sample. The distribution of a censored variable is a mixture between a continuous and a categorical distributions. In this case, results from lineal regression models, by means of ordinary least squares, will provide biased estimates. With one only censorhip point the tobit model must be used, while with several censorship points this model's generalization should also be used. The illustration of these models is presented through the analysis of the levels of mercury measured in urine in the study about health effects of a municipal solid-waste incinerator in the county of Mataró (Spain).

Adult↗
PubMedDate not supplied

[Impact of air pollution on the mortality and emergencies of chronic obstructive pulmonary disease and asthma in Barcelona].

OBJECTIVES: Air pollution has been associated with increased mortality according to studies carried out in the US. The APHEA project (Air Pollution on Health: a European Approach) analyzes the short-term effects in 15 european cities. We evaluated the acute relation between air pollution, mortality, and hospital emergency-room visits in Barcelona, one of the cities participating in the APHEA project. METHODS: Daily variations in total mortality, cardiovascular mortality, respiratory mortality, and emergency-room visits for chronic obstructive pulmonary disease (COPD), and asthma were studied in relation to daily variations in air pollution levels in 1985-1991. Poisson regression was done and temperature, relative humidity, and epidemics of asthma and flu were controlled. Temporal trends and auto-regressive terms were examined. RESULTS: A reduction of about 50 micrograms/m3 in particles and sulfur dioxide was accompanied by a reduction of about 4% and 6% (p < 0.05), respectively, in daily deaths from respiratory and cardiovascular causes and emergency-room visits for COPD. Oxidant pollutants (nitrogen dioxide and ozone) were related positively with cardiovascular mortality and emergency visits for COPD and asthma. The role of ozone was notable, with a reduction in ozone levels of 50 micrograms/m3 originating a 4% reduction in emergency-room visits for COPD and asthma (p < 0.05). CONCLUSIONS: Current levels of air pollutants had an epidemiologically measurable impact on mortality and emergency-room visits in Barcelona. These results were consistent with the findings of similar studies in other european and american cities and with previous studies of emergency-room admissions in Barcelona. These studies suggest the possible toxicity of air pollution.

Air Pollutants↗