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Education, intelligence and Alzheimer’s disease: evidence from a multivariable two-sample Mendelian randomization study

Research output: Contribution to journalArticle

Original languageEnglish
Article numberdyz280
Number of pages10
JournalInternational Journal of Epidemiology
DOIs
DateAccepted/In press - 3 Jan 2020
DatePublished (current) - 31 Jan 2020

Abstract

Objectives
To examine whether educational attainment and intelligence have causal effects on risk of Alzheimer’s disease (AD), independently of each other.

Design
Two-sample univariable and multivariable Mendelian randomization (MR) to estimate the causal effects of education on intelligence and vice versa, and the total and independent causal effects of both education and intelligence on AD risk.

Participants
17 008 AD cases and 37 154 controls from the International Genomics of Alzheimer’s Project (IGAP) consortium.

Main outcome measure
Odds ratio (OR) of AD per standardized deviation increase in years of schooling (SD = 3.6 years) and intelligence (SD = 15 points on intelligence test).

Results
There was strong evidence of a causal, bidirectional relationship between intelligence and educational attainment, with the magnitude of effect being similar in both directions [OR for intelligence on education = 0.51 SD units, 95% confidence interval (CI): 0.49, 0.54; OR for education on intelligence = 0.57 SD units, 95% CI: 0.48, 0.66]. Similar overall effects were observed for both educational attainment and intelligence on AD risk in the univariable MR analysis; with each SD increase in years of schooling and intelligence, odds of AD were, on average, 37% (95% CI: 23–49%) and 35% (95% CI: 25–43%) lower, respectively. There was little evidence from the multivariable MR analysis that educational attainment affected AD risk once intelligence was taken into account (OR = 1.15, 95% CI: 0.68–1.93), but intelligence affected AD risk independently of educational attainment to a similar magnitude observed in the univariate analysis (OR = 0.69, 95% CI: 0.44–0.88).

Conclusions
There is robust evidence for an independent, causal effect of intelligence in lowering AD risk. The causal effect of educational attainment on AD risk is likely to be mediated by intelligence.

    Research areas

  • alzheimer's disease, educational status, intelligence, mendelian randomization analysis, Education, dementia, Alzheimer’s disease, Mendelian randomization

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    Rights statement: This is the final published version of the article (version of record). It first appeared online via Oxford University Press at https://academic.oup.com/ije/advance-article/doi/10.1093/ije/dyz280/5719343. Please refer to any applicable terms of use of the publisher.

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