Comparing meta-analysis and ecological-longitudinal analysis in time-series studies : a case study of the effects of air pollution on mortality in three Spanish cities

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dc.contributor.author Sáez Zafra, Marc
dc.contributor.author Figueiras, Adolfo
dc.contributor.author Ballester, Ferran
dc.contributor.author Pérez Hoyos, Santiago
dc.contributor.author Ocaña, Ricardo
dc.contributor.author Tobías, Aurelio
dc.date.issued 2001
dc.identifier.citation Saez, M., Figueiras, A., Ballester,F., Perez-Hoyos,S., Ocaña, R., i Tobias, A. (2001). Comparing meta-analysis and ecological-longitudinal analysis in time-series studies : a case study of the effects of air pollution on mortality in three Spanish cities. Journal of Epidemiology and Community Health, 55 (6), 423–432. Recuperat 12 setembre 2011, a http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1731914/
dc.identifier.issn 0143-005X (versió paper)
dc.identifier.issn 1470-2738 (versió electrònica)
dc.identifier.uri http://hdl.handle.net/10256/3541
dc.description.abstract The objective of this paper is to introduce a diVerent approach, called the ecological-longitudinal, to carrying out pooled analysis in time series ecological studies. Because it gives a larger number of data points and, hence, increases the statistical power of the analysis, this approach, unlike conventional ones, allows the complementation of aspects such as accommodation of random effect models, of lags, of interaction between pollutants and between pollutants and meteorological variables, that are hardly implemented in conventional approaches. Design—The approach is illustrated by providing quantitative estimates of the short-termeVects of air pollution on mortality in three Spanish cities, Barcelona,Valencia and Vigo, for the period 1992–1994. Because the dependent variable was a count, a Poisson generalised linear model was first specified. Several modelling issues are worth mentioning. Firstly, because the relations between mortality and explanatory variables were nonlinear, cubic splines were used for covariate control, leading to a generalised additive model, GAM. Secondly, the effects of the predictors on the response were allowed to occur with some lag. Thirdly, the residual autocorrelation, because of imperfect control, was controlled for by means of an autoregressive Poisson GAM. Finally, the longitudinal design demanded the consideration of the existence of individual heterogeneity, requiring the consideration of mixed models. Main results—The estimates of the relative risks obtained from the individual analyses varied across cities, particularly those associated with sulphur dioxide. The highest relative risks corresponded to black smoke in Valencia. These estimates were higher than those obtained from the ecological-longitudinal analysis. Relative risks estimated from this latter analysis were practically identical across cities, 1.00638 (95% confidence intervals 1.0002, 1.0011) for a black smoke increase of 10 μg/m3 and 1.00415 (95% CI 1.0001, 1.0007) for a increase of 10 μg/m3 of sulphur dioxide. Because the statistical power is higher than in the individual analysis more interactions were statistically significant,especially those among air pollutants and meteorological variables. Conclusions—Air pollutant levels were related to mortality in the three cities of the study, Barcelona, Valencia and Vigo. These results were consistent with similar studies in other cities, with other multicentric studies and coherent with both, previous individual, for each city, and multicentric studies for all three cities
dc.format.mimetype application/pdf
dc.language.iso eng
dc.publisher BMJ Publishing Group
dc.relation.ispartof Journal of Epidemiology and Community Health, 2001, vol. 55, núm. 6, p.423-432
dc.relation.ispartofseries Articles publicats (D-EC)
dc.rights Aquest document està subjecte a una llicència Creative Commons: Reconeixement – No comercial (by-nc)
dc.rights.uri http://creativecommons.org/licenses/by-nc/3.0/es/deed.ca
dc.subject Aire -- Contaminació
dc.subject Contaminants
dc.subject Mortalitat
dc.subject Air -- Pollution
dc.subject Mortality
dc.subject Pollutants
dc.title Comparing meta-analysis and ecological-longitudinal analysis in time-series studies : a case study of the effects of air pollution on mortality in three Spanish cities
dc.type info:eu-repo/semantics/article


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