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Alzheimers Dement. 2015 Dec;11(12):1439-1451. doi: 10.1016/j.jalz.2015.05.015. Epub 2015 Jun 12.

Genetically predicted body mass index and Alzheimer's disease-related phenotypes in three large samples: Mendelian randomization analyses.

Author information

1
Department of Medicine, University of Washington, Seattle, WA, USA.
2
Department of Epidemiology and Biostatistics, University of California at San Francisco, San Francisco, CA, USA.
3
Department of Biology, Brigham Young University, Provo, UT, USA.
4
Department of Radiology, Indiana University, Indianapolis, IN, USA.
5
Department of Neurology, Rush University, Chicago, IL, USA.
6
Group Health Research Institute, Seattle, WA, USA.
7
Department of Epidemiology and Biostatistics, University of California at San Francisco, San Francisco, CA, USA. Electronic address: mglymour@epi.ucsf.edu.

Abstract

Observational research shows that higher body mass index (BMI) increases Alzheimer's disease (AD) risk, but it is unclear whether this association is causal. We applied genetic variants that predict BMI in Mendelian randomization analyses, an approach that is not biased by reverse causation or confounding, to evaluate whether higher BMI increases AD risk. We evaluated individual-level data from the AD Genetics Consortium (ADGC: 10,079 AD cases and 9613 controls), the Health and Retirement Study (HRS: 8403 participants with algorithm-predicted dementia status), and published associations from the Genetic and Environmental Risk for AD consortium (GERAD1: 3177 AD cases and 7277 controls). No evidence from individual single-nucleotide polymorphisms or polygenic scores indicated BMI increased AD risk. Mendelian randomization effect estimates per BMI point (95% confidence intervals) were as follows: ADGC, odds ratio (OR) = 0.95 (0.90-1.01); HRS, OR = 1.00 (0.75-1.32); GERAD1, OR = 0.96 (0.87-1.07). One subscore (cellular processes not otherwise specified) unexpectedly predicted lower AD risk.

KEYWORDS:

Alzheimer's disease; Dementia; Mendelian randomization; Obesity

PMID:
26079416
PMCID:
PMC4676945
DOI:
10.1016/j.jalz.2015.05.015
[Indexed for MEDLINE]
Free PMC Article

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