CVD risk lessens with more years in school

Body mass index, systolic blood pressure and smoking behaviors mediate the effects of education on cardiovascular health, according to a recent study in The BMJ.

We know education seems to have a protective effect on heart health, first author Alice R. Carter, a PhD candidate at the University of Bristol, and co-authors said—lower levels of education are causally related to a higher risk of CVD, and a 2017 study found an extra three and a half years of schooling could cut a person’s risk of coronary heart disease by as much as one-third. But researchers worry those studies might suffer from some bias, and unlike a lot of other cardiovascular risk factors, education is inherently difficult to intervene on.

Rather than rely on observational mediation analyses and risk bias, Carter and her team took a Mendelian randomization approach to their study of the relationship between education inequality and CVD. Mendelian randomization uses genetic variants to estimate the effect of a certain exposure on an outcome of interest, exploiting the random allocation of variants to infer causal effects that are robust to measurement error and confounding. Using data from the UK Biobank, the authors examined three exposures—BMI, systolic BP and smoking status—on patients’ CV health and level of education.

They found each additional standard deviation of education of 3.6 years corresponded with a 13% lower risk of coronary heart disease in observational analysis and a 37% lower risk in Mendelian randomization analysis. BMI was estimated to mediate 15% and 18% of total risk reduction in observational and Mendelian analyses, respectively, while systolic BP mediated 11% and 19% and smoking behavior mediated 19% and 34%.

As a whole, the trio of risk factors were estimated to mediate 42% and 36% of the effect of education on coronary heart disease in observational and Mendelian analyses, respectively. Carter et al. said similar results were found when estimating risk for stroke, MI and CVD.

“Our observational and genetic analyses support that the effect of education on the risk of cardiovascular disease is mediated by approximately up to one-third through any of BMI, systolic blood pressure or smoking behavior,” the authors wrote. “By using distinct analytical methods, including genetic approaches that can draw causal inference, our results suggest that interventions aimed at reducing BMI, systolic blood pressure and smoking behavior in European populations would lead to reductions in cases of cardiovascular disease attributable to lower levels of education.”

Carter and colleagues said it’s important to note, however, that their study still fails to explain more than half of the effect of education has on CVD risk. Their work didn’t consider a host of other factors that likely also contribute to risk, including exercise, diet, health system factors, lipid profiles and glycemic traits.

“The findings of this study have notable implications for policymakers as they identify potential strategies for reducing education inequalities in health,” the authors said. “Further research identifying the other related factors and the interplay between them will be key to reducing social inequalities in cardiovascular disease. Furthermore, work investigating more diverse populations will be necessary to support the extrapolation of these findings outside of the considered contexts.”