title: Methods for pooling results of epidemiologic studies: the Pooling Project of Prospective Studies of Diet and Cancer.
abstract: With the growing number of epidemiologic publications on the relation between dietary factors and cancer risk, pooled analyses that summarize results from multiple studies are becoming more common. Here, the authors describe the methods being used to summarize data on diet-cancer associations within the ongoing Pooling Project of Prospective Studies of Diet and Cancer, begun in 1991. In the Pooling Project, the primary data from prospective cohort studies meeting prespecified inclusion criteria are analyzed using standardized criteria for modeling of exposure, confounding, and outcome variables. In addition to evaluating main exposure-disease associations, analyses are also conducted to evaluate whether exposure-disease associations are modified by other dietary and nondietary factors or vary among population subgroups or particular cancer subtypes. Study-specific relative risks are calculated using the Cox proportional hazards model and then pooled using a random- or mixed-effects model. The study-specific estimates are weighted by the inverse of their variances in forming summary estimates. Most of the methods used in the Pooling Project may be adapted for examining associations with dietary and nondietary factors in pooled analyses of case-control studies or case-control and cohort studies combined.
authors.affiliation: Department of Medicine, Brigham and Women's Hospital and Department of Nutrition, Harvard School of Public Health, Boston, MA 02115, USA. pooling@hsphsun2.harvard.edu
authors.forename: Stephanie A
authors.initials: SA
authors.lastname: Smith-Warner
authors.forename: Donna
authors.initials: D
authors.lastname: Spiegelman
authors.forename: John
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authors.lastname: Ritz
authors.forename: Demetrius
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authors.lastname: Albanes
authors.forename: W Lawrence
authors.initials: WL
authors.lastname: Beeson
authors.forename: Leslie
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authors.lastname: Bernstein
authors.forename: Franco
authors.initials: F
authors.lastname: Berrino
authors.forename: Piet A
authors.initials: PA
authors.lastname: van den Brandt
authors.forename: Julie E
authors.initials: JE
authors.lastname: Buring
authors.forename: Eunyoung
authors.initials: E
authors.lastname: Cho
authors.forename: Graham A
authors.initials: GA
authors.lastname: Colditz
authors.forename: Aaron R
authors.initials: AR
authors.lastname: Folsom
authors.forename: Jo L
authors.initials: JL
authors.lastname: Freudenheim
authors.forename: Edward
authors.initials: E
authors.lastname: Giovannucci
authors.forename: R Alexandra
authors.initials: RA
authors.lastname: Goldbohm
authors.forename: Saxon
authors.initials: S
authors.lastname: Graham
authors.forename: Lisa
authors.initials: L
authors.lastname: Harnack
authors.forename: Pamela L
authors.initials: PL
authors.lastname: Horn-Ross
authors.forename: Vittorio
authors.initials: V
authors.lastname: Krogh
authors.forename: Michael F
authors.initials: MF
authors.lastname: Leitzmann
authors.forename: Marjorie L
authors.initials: ML
authors.lastname: McCullough
authors.forename: Anthony B
authors.initials: AB
authors.lastname: Miller
authors.forename: Carmen
authors.initials: C
authors.lastname: Rodriguez
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Rohan
authors.forename: Arthur
authors.initials: A
authors.lastname: Schatzkin
authors.forename: Roy
authors.initials: R
authors.lastname: Shore
authors.forename: Mikko
authors.initials: M
authors.lastname: Virtanen
authors.forename: Walter C
authors.initials: WC
authors.lastname: Willett
authors.forename: Alicja
authors.initials: A
authors.lastname: Wolk
authors.forename: Anne
authors.initials: A
authors.lastname: Zeleniuch-Jacquotte
authors.forename: Shumin M
authors.initials: SM
authors.lastname: Zhang
authors.forename: David J
authors.initials: DJ
authors.lastname: Hunter
mesh_terms: D004032:Diet; D004812:Epidemiologic Methods; D006801:Humans; D009369:Neoplasms / Q000453:epidemiology*; D011446:Prospective Studies; D012307:Risk Factors; D013223:Statistics as Topic