Abstract
Causes of the association between cognitive ability and health remain unknown, but may reflect a shared genetic aetiology. This study examines the causal genetic associations between cognitive ability and physical health. We carried out two-sample Mendelian randomization analyses using the inverse-variance weighted method to test for causality between later life cognitive ability, educational attainment (as a proxy for cognitive ability in youth), BMI, height, systolic blood pressure, coronary artery disease, and type 2 diabetes using data from six independent GWAS consortia and the UK Biobank sample (N = 112 151). BMI, systolic blood pressure, coronary artery disease and type 2 diabetes showed negative associations with cognitive ability; height was positively associated with cognitive ability. The analyses provided no evidence for casual associations from health to cognitive ability. In the other direction, higher educational attainment predicted lower BMI, systolic blood pressure, coronary artery disease, type 2 diabetes, and taller stature. The analyses indicated no causal association from educational attainment to physical health. The lack of evidence for causal associations between cognitive ability, educational attainment, and physical health could be explained by weak instrumental variables, poorly measured outcomes, or the small number of disease cases.
Highlights
IntroductionLower educational attainment and greater cognitive decline are all associated with poorer health outcomes[1,2,3]
Lower cognitive ability, lower educational attainment and greater cognitive decline are all associated with poorer health outcomes[1,2,3]
A 1 SD higher Body mass index (BMI) was associated with a 0.05 SD lower score for cognitive ability (β = −0.05, 95% CI = −0.06, −0.04)
Summary
Lower educational attainment and greater cognitive decline are all associated with poorer health outcomes[1,2,3]. A negative genetic correlation has been identified between BMI, but not blood pressure, and educational attainment and cognitive ability in mid to late life[4, 5], and a polygenic score for higher BMI is associated with lower cognitive ability in mid to late life and lower educational attainment[4]; www.nature.com/scientificreports/. A polygenic score for higher systolic blood pressure is associated with lower educational attainment, but higher cognitive ability in mid to late life[4]. A polygenic risk score for coronary artery disease is associated with lower educational attainment and lower mid to late life cognitive ability[4], and a negative genetic correlation was identified between coronary artery disease and educational attainment[4, 5], but not cognitive ability in mid to late life[4]
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