Education protects against coronary heart disease and stroke independently of cognitive function: evidence from Mendelian randomization

BACKGROUND: There is evidence that education protects against cardiovascular disease. However, it is not known whether such an effect is independent of cognition. METHODS: We performed two-sample Mendelian randomization (MR) analyses to investigate the effect of education and cognition, respectively, on risk of CHD and ischaemic stroke. Additionally, we used multivariable MR to adjust for the effects of cognition and education in the respective analyses to measure the effects of these traits independently of each other. RESULTS: In unadjusted MR, there was evidence that education is causally associated with both CHD and stroke risk [CHD: odds ratio (OR) 0.65 per 1-standard deviation (SD; 3.6 years) increase in education; 95% confidence interval (CI) 0.61-0.70, stroke: OR 0.77; 95% CI 0.69-0.86]. This effect persisted after adjusting for cognition in multivariable MR (CHD: OR 0.76; 95% CI 0.65-0.89, stroke OR 0.74; 95% CI 0.59-0.92). Cognition had an apparent effect on CHD risk in unadjusted MR (OR per 1-SD increase 0.80; 95% CI 0.74-0.85), however after adjusting for education this was no longer observed (OR 1.03; 95% CI 0.86-1.25). Cognition did not have any notable effect on the risk of developing ischaemic stroke, with (OR 0.97; 95% CI 0.87-1.08) or without adjustment for education (OR 1.04; 95% CI 0.79-1.36). CONCLUSIONS: This study provides evidence to support that education protects against CHD and ischaemic stroke risk independently of cognition, but does not provide evidence to support that cognition protects against CHD and stroke risk independently of education. These findings could have implications for education and health policy.