title: [Meta-analysis or pooled analysis? A comparison based on time-series used for the analysis of short-term effects of air pollution on human health].
abstract: OBJECTIVE
  to compare the meta-analysis and the pooled analysis approach to study short-term effects of air pollution on human health in Emilia-Romagna Region (Central Italy) cities, characterised by strong homogeneity of environmental and sociodemographic features.
  
  
  METHODS
  application of fixed-effects meta-analysis and fixed-effects pooled analysis on time-series data of seven cities in Emilia-Romagna in the period 2006-2010. The relationship among adverse health events (deaths due to natural causes, cardiovascular disease, cerebrovascular disease and respiratory disease) and concentrations of PM10, PM2.5 and NO2 was investigated by means of GAM models, using the EpiAir protocol.
  
  
  RESULTS
  the pooled analysis application entailed a gain in terms of precision of effect estimates in respect to meta-analysis approach. The interval widths of pooled analysis are lower than those of meta-analytic estimates, with percentage reductions between 7% and 43%. This power increase led to a major number of statistically significant pooled analysis estimates. It has been a generally good correspondence between the two methods in terms of direction and strength of the association among health outcomes and the various pollutants. An exception is the PM10 effect estimate on respiratory mortality, where the meta-analytic estimate was significantly higher and not in line with literature data.
  
  
  CONCLUSIONS
  the study highlighted the increase in accuracy and stability of effect estimates obtained from a pooled analysis compared to a meta-analysis in a regional context such as the Emilia-Romagna Region, characterised by the absence of heterogeneity in exposure to pollutants and other confounders. In this context, the pooled approach is to be considered preferable to meta-analysis.
authors.affiliation: Centro tematico ambiente e salute, Direzione tecnica, Agenzia regionale prevenzione e ambiente Emilia-Romagna, Modena. bianca.gherardi2@unibo.it.|Dipartimento di scienze statistiche, Università di Bologna.
authors.forename: Bianca
authors.initials: B
authors.lastname: Gherardi
authors.affiliation: Dipartimento di scienze statistiche, Università di Bologna.|Centro tematico ambiente e salute, Direzione tecnica, Agenzia regionale prevenzione e ambiente Emilia-Romagna, Modena. giulia.tommaso2@unibo.it.
authors.forename: Giulia
authors.initials: G
authors.lastname: Tommaso
authors.affiliation: Centro tematico ambiente e salute, Direzione tecnica, Agenzia regionale prevenzione e ambiente Emilia-Romagna, Modena.
authors.forename: Andrea
authors.initials: A
authors.lastname: Ranzi
authors.affiliation: Centro tematico ambiente e salute, Direzione tecnica, Agenzia regionale prevenzione e ambiente Emilia-Romagna, Modena.
authors.forename: Stefano
authors.initials: S
authors.lastname: Zauli Sajani
authors.affiliation: Dipartimento di sanità pubblica, AUSL Ferrara.
authors.forename: Aldo
authors.initials: A
authors.lastname: De Togni
authors.affiliation: UOC epidemiologia, promozione della salute e comunicazione del rischio, UOS rischio ambientale, Dipartimento di sanità pubblica, Azienda USL di Bologna.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Pizzi
authors.affiliation: Centro tematico ambiente e salute, Direzione tecnica, Agenzia regionale prevenzione e ambiente Emilia-Romagna, Modena.
authors.forename: Paolo
authors.initials: P
authors.lastname: Lauriola
mesh_terms: D000393:Air Pollutants / Q000032:analysis; D000397:Air Pollution / Q000009:adverse effects*; D002318:Cardiovascular Diseases / Q000401:mortality; D002423:Cause of Death; D002561:Cerebrovascular Disorders / Q000401:mortality; D066264:Datasets as Topic; D004782:Environmental Health; D006801:Humans; D007558:Italy / Q000453:epidemiology; D015201:Meta-Analysis as Topic; D008962:Models, Theoretical; D010316:Particle Size; D052638:Particulate Matter / Q000032:analysis; D012140:Respiratory Tract Diseases / Q000401:mortality; D012621:Seasons; D014504:Urban Health
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter