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Andrew Smith
Dietary patterns in the ALSPAC cohort: Cluster analysisEUCCONET International Workshop 18th October 2011
Andrew Smith
Dietary patterns in the ALSPAC cohort: Cluster analysis
Pauline Emmett
P. K. Newby
Kate Northstone
World Cancer Research Fund
Dietary patterns
• Examine diet as a whole
• Start with many variables
(e.g. FFQ, diet diary)
• Express as a small number of
variables
Image: Paul / FreeDigitalPhotos.net
Principal components analysis (PCA)
• Examine diet as a whole
• Start with many variables
(e.g. FFQ, diet diary)
• Use correlations between foods
• Express as a small number of
components
Image: Paul / FreeDigitalPhotos.net
Cluster analysis
• Examine diet as a whole
• Start with many variables
(e.g. FFQ, diet diary)
• Use similarities between people
• Express as a small number of
clusters
Image: Paul / FreeDigitalPhotos.net
Dietary patterns studies in ALSPAC
Source PCA Cluster
Mothers’ FFQ Northstone and Emmett, 2008a
Partners’ FFQ Northstone and Emmett, 2010
FFQ age 3 North, Emmett et al. 2000
FFQ age 4½ Northstone, Emmett et al. 2005
FFQ age 7 Northstone, Emmett et al. 2005 Smith et al. 2011
FFQ age 9 Northstone and Emmett, 2008b
Diet diary age 10 in submission
FFQs age 13 in submission
Case study: PCA of FFQ age 7
Northstone and Emmett, 2005
Image: Suat Eman, winnond / FreeDigitalPhotos.net
Junk
Traditional
Health conscious
Dietary patterns studies in ALSPAC
Source PCA Cluster
Mothers’ FFQ Northstone and Emmett, 2008a
Partners’ FFQ Northstone and Emmett, 2010
FFQ age 3 North, Emmett et al. 2000
FFQ age 4½ Northstone, Emmett et al. 2005
FFQ age 7 Northstone, Emmett et al. 2005 Smith et al. 2011
FFQ age 9 Northstone and Emmett, 2008b
Diet diary age 10 in submission
FFQs age 13 in submission
Cluster analysis
• k-means is most
widely-used method
• Must avoid pitfalls– Standardization– Algorithm– Reliability
Image: Boaz Yiftach / FreeDigitalPhotos.net
Dietary patterns studies in ALSPAC
Source PCA Cluster
Mothers’ FFQ Northstone and Emmett, 2008a
Partners’ FFQ Northstone and Emmett, 2010
FFQ age 3 North, Emmett et al. 2000
FFQ age 4½ Northstone, Emmett et al. 2005
FFQ age 7 Northstone, Emmett et al. 2005 Smith et al. 2011
FFQ age 9 Northstone and Emmett, 2008b
Diet diary age 10 in submission
FFQs age 13 in submission
Case study: cluster analysis of FFQ age 7
• FFQ administered to ALSPAC children at 81 months of
age
• Input variables are the same as PCA
(Northstone, Emmett et al. 2005)
• 8,279 children
• 3 clusters
• Smith et al. 2011
Case study: cluster analysis of FFQ age 7
Processed 4177 children
White breadProcessed meatFizzy drinksIce cream
CrispsChipsSquashBiscuits and sweets
Plant-based
2065 children
Brown/wholemeal breadFruit and vegetablesVegetarian foods
PastaRiceCereals
Traditional British
2037 children
MeatPotatoes
Full-fat milk
Similarities with PCA
Cluster analysis of diet diary data
• 7473 children aged 10
• Advantages– Similar 3-cluster solution
(Processed, Plant-based, Traditional British)– Good separation between clusters
• Disadvantages– Not robust to under-reporting– PCA shows better associations with fat mass
Dietary patterns studies in ALSPAC
Source PCA Cluster
Mothers’ FFQ Northstone and Emmett, 2008a
Partners’ FFQ Northstone and Emmett, 2010
FFQ age 3 North, Emmett et al. 2000
FFQ age 4½ Northstone, Emmett et al. 2005
FFQ age 7 Northstone, Emmett et al. 2005 Smith et al. 2011
FFQ age 9 Northstone and Emmett, 2008b
Diet diary age 10 in submission
FFQs age 13 in submission
Dietary patterns studies in ALSPAC
Source PCA ClusterMothers’ FFQ Northstone and Emmett, 2008a. Br J Nutr.
99 p.1099-106
Partners’ FFQ Northstone and Emmett, 2010. EJCN 64 p.978-86
FFQ age 3 North, Emmett and the ALSPAC Study Team, 2000. EJCN 54 p.73-80
FFQ age 7 Northstone, Emmett and the ALSPAC Study team, 2005. EJCN 59 p.751-60
Smith, Emmett, Newby, Northstone 2011. EJCN 65 p.1102-9
FFQ age 9 Northstone and Emmett, 2008b. Br J Nutr 100 p.1069-76
Diet diary age 10 in submission
FFQs age 13 in submission