Western diet is associated with a smaller hippocampus: a longitudinal investigation.
BACKGROUND
Recent meta-analyses confirm a relationship between diet quality and both depression and cognitive health in adults. While the biological pathways that underpin these relationships are likely multitudinous, extensive evidence from animal studies points to the involvement of the hippocampus. The aim of this study was to examine the association between dietary patterns and hippocampal volume in humans, and to assess whether diet was associated with differential rates of hippocampal atrophy over time.


METHODS
Data were drawn from the Personality and Total Health Through Life Study and focused on a subsample of the cohort (n = 255) who were aged 60-64 years at baseline in 2001, completed a food frequency questionnaire, and underwent two magnetic resonance imaging scans approximately 4 years apart. Longitudinal generalized estimating equation linear regression models were used to assess the association between dietary factors and left and right hippocampal volumes over time.


RESULTS
Every one standard deviation increase in healthy "prudent" dietary pattern was associated with a 45.7 mm(3) (standard error 22.9 mm(3)) larger left hippocampal volume, while higher consumption of an unhealthy "Western" dietary pattern was (independently) associated with a 52.6 mm(3) (SE 26.6 mm(3)) smaller left hippocampal volume. These relationships were independent of covariates including age, gender, education, labour-force status, depressive symptoms and medication, physical activity, smoking, hypertension and diabetes. While hippocampal volume declined over time, there was no evidence that dietary patterns influenced this decline. No relationships were observed between dietary patterns and right hippocampal volume.


CONCLUSIONS
Lower intakes of nutrient-dense foods and higher intakes of unhealthy foods are each independently associated with smaller left hippocampal volume. To our knowledge, this is the first human study to demonstrate associations between diet and hippocampal volume concordant with data previously observed in animal models.
Division of Nutritional Psychiatry Research, IMPACT Strategic Research Centre, Deakin University, Geelong, Australia. f.jacka@deakin.edu.au.|Department of Psychiatry, The University of Melbourne, Melbourne, Australia. f.jacka@deakin.edu.au.|Centre for Adolescent Health, Murdoch Children's Research Institute, Melbourne, Australia. f.jacka@deakin.edu.au.|Black Dog Institute, Sydney, Australia. f.jacka@deakin.edu.au.
Felice N
FN
Jacka
Centre for Research on Ageing, Health and Wellbeing, Research School of Population Health, The Australian National University, Canberra, Australia. nicolas.cherbuin@anu.edu.au.
Nicolas
N
Cherbuin
Centre for Research on Ageing, Health and Wellbeing, Research School of Population Health, The Australian National University, Canberra, Australia. kaarin.anstey@anu.edu.au.
Kaarin J
KJ
Anstey
Centre for Healthy Brain Ageing (CHeBA), School of Psychiatry, Faculty of Medicine, University of New South Wales, Sydney, Australia. p.sachdev@unsw.edu.au.
Perminder
P
Sachdev
Centre for Research on Ageing, Health and Wellbeing, Research School of Population Health, The Australian National University, Canberra, Australia. peter.butterworth@anu.edu.au.
Peter
P
Butterworth
D015331:Cohort Studies; D066273:Diet, Western / Q000009:adverse effects*; D005260:Female; D006624:Hippocampus / Q000473:pathology*; D006801:Humans; D016014:Linear Models; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged