Methods for pooling results of epidemiologic studies: the Pooling Project of Prospective Studies of Diet and Cancer.
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.
Smith-Warner
Stephanie A
SA
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
Spiegelman
Donna
D
Ritz
John
J
Albanes
Demetrius
D
Beeson
W Lawrence
WL
Bernstein
Leslie
L
Berrino
Franco
F
van den Brandt
Piet A
PA
Buring
Julie E
JE
Cho
Eunyoung
E
Colditz
Graham A
GA
Folsom
Aaron R
AR
Freudenheim
Jo L
JL
Giovannucci
Edward
E
Goldbohm
R Alexandra
RA
Graham
Saxon
S
Harnack
Lisa
L
Horn-Ross
Pamela L
PL
Krogh
Vittorio
V
Leitzmann
Michael F
MF
McCullough
Marjorie L
ML
Miller
Anthony B
AB
Rodriguez
Carmen
C
Rohan
Thomas E
TE
Schatzkin
Arthur
A
Shore
Roy
R
Virtanen
Mikko
M
Willett
Walter C
WC
Wolk
Alicja
A
Zeleniuch-Jacquotte
Anne
A
Zhang
Shumin M
SM
Hunter
David J
DJ
D004032:Diet; D004812:Epidemiologic Methods; D006801:Humans; D009369:Neoplasms / Q000453:epidemiology*; D011446:Prospective Studies; D012307:Risk Factors; D013223:Statistics as Topic