Biomedical subjects

Margarita Taracido

Publications and source records attributed to Margarita Taracido.

3 recordsLinked to original sources

PubMed2005

Analysis of case-crossover designs using longitudinal approaches: a simulation study.

BACKGROUND: Application of case-crossover designs provides an alternative to time-series analysis for analyzing the health-related effects of air pollution. Although some case-crossover studies can control for trend and seasonality by design, to date they have been analyzed as matched case-control studies. Such analyses may exhibit biases and a lower statistical efficiency than traditional time series analyzed with Poisson. METHODS: In this article, case-crossover studies are treated as cohort studies in which each subject is observed for a short period of time before and/or after the event, thus making possible analyzing with Andersen-Gill and generalized linear mixed models. We conducted a simulation study to compare the behavior of these models applied to case-crossover designs with time series analyzed with Poisson and with case-crossover analyzed by conditional logistic regression. To this end, we created a random variable that follows a Poisson distribution of low (2/day) and high mean events (22/day). This variable is a function of an unobserved confounding variable (that introduces trend and seasonality) and data on small particulate matter (PM10) from Barcelona. In addition, scenarios were created to assess the effect on exposure exerted by autocorrelation and the magnitude of the pollutant coefficient. RESULTS: The full semisymmetric design analyzed with generalized linear mixed models yields good coverage and a high statistical power for air-pollution effect magnitudes close to the real values but shows bias for high effect magnitudes. This bias seems to be attributable to autocorrelation in the exposure variable. CONCLUSIONS: Longitudinal approaches applied to case-crossover designs may prove useful for analyzing the acute effects of environmental exposures.

Air Pollutants↗

PubMed2003

[Short-term relationship between air pollution and mortality in 13 Spanish cities].

BACKGROUND AND OBJECTIVE: EMECAM is a collaborative project that seeks to evaluate the short-term effects of air pollution on mortality in Spain. MATERIAL AND METHOD: We collected data for air pollutants (particles and gases), daily mortality (total except external, cardiovascular and respiratory causes) and co-variables (temperature, humidity, influenza and calendar variables) in 13 Spanish cities. The magnitude of the association in every city was estimated using GAM under a Poisson distribution. Combined estimates for each cause and pollutant were obtained under 'fixed effects' and 'random effects'models. RESULTS: An increase of 10 (g/m3 in the levels of the average of the concurrent and one day lag for black smoke was associated with a 0.8% (CI: 0.4-1.1) increase in mortality. The same increase in the concentration of SO2 was associated with a 0.5% (CI: 0.1-1.0) increase in daily deaths, and a 0.6% (CI: 0.3-0.8) increase in the case of NO2. An increase of 1 mg/m3 in the levels of CO was associated with an increase of 1.5% (CI: 0.5-2.6) in daily deaths. CONCLUSIONS: There is a short-term association between increases of daily levels of air pollutants and the number of daily deaths in Spanish cities.

Air Pollution↗

PubMedDate not supplied

[The EMECAS Project: Spanish multicentre study on short-term health effects of air pollution].

UNLABELLED: The EMECAM Project demonstrated the short-term effect of air pollution on the death rate in 14 cities in Spain throughout the 1990-1995 period. The Spanish Multicentre Study on Health Effects of Air Pollution (EMECAS) is broadening these objectives by incorporating more recent data, information on hospital disease admissions and totaling 16 Spanish cities. This is an ecological time series study in which the response variables are the daily deaths and the emergency hospitalizations due to circulatory system diseases and respiratory diseases among the residents in each city. Pollutants analyses: suspended particles, SO2, NO2, CO and O3. Control variables: meteorological, calendar, seasonality and influenza trend and incidence. STATISTICAL ANALYSIS: estimate of the association in each city by means of the construction of generalized additive Poisson regression models and metanalysis for obtaining combined estimators. The EMECAS Project began with the creation of three working groups (Exposure, Epidemiology and Analysis Methodology) which defined the protocol. The average levels of pollutants were below those established under the current regulations for sulfur dioxide, carbon monoxide and ozone. The NO2 and PM10 values were around those established under the regulations (40 mg/m3). This is the first study of the relationship between air pollution and disease rate among one group of Spanish cities. The pollution levels studied are moderate for some pollutants, although for others, especially NO2 and particles, these levels could entail a problem with regard to complying with the regulations in force.

Air Pollution↗