Epigenetic footprints of educational attainment

New research shows that there are differences between higher- and lower-educated Dutch people in how white blood cells use the genetic code. The differences are not in the letters of the DNA code, but in information surrounding the DNA - the so-called epigenome. This is the result of research by scientists of the Netherlands Twin Register from the Vrije Universiteit Amsterdam (VU) in collaboration with researchers from the BBMRI-NL BIOS (Biobank-based Integrative Omics Studies) consortium.

03/27/2018 | 5:03 PM

The relationship between education and health
Even though the Netherlands currently is one of the wealthiest and most highly educated countries in the world, significant health differences exist between higher and lower educated Dutch people, with lower educated people having a lower life expectancy in the order of 6 to 7 years. The researchers discovered associations between educational attainment - the highest completed level of education of an adult person - and DNA modifications, by analyzing epigenome data in blood samples from over 4000 Dutch individuals from four Dutch cohorts (Lifelines, The Leiden Longevity Study, The Rotterdam Study and the Netherlands Twin Register). These findings bring us one step closer to understanding the causes of health differences between higher and lower educated people that exist even in the Netherlands, because the epigenome is responsible for controlling which parts of the DNA-code (genes) are switched off and which ones are switched on (and how much). The results have been published today in NPJ Science of learning.

The environment can influence the functioning of genes
There are switches in our DNA that control the expression of the DNA sequence (the epigenome). An important component of these switches is DNA methylation. Several studies have already suggested that some environmental exposures can influence the degree of methylation of certain genes, which can make these genes more or less active. VU-researcher and first author Jenny van Dongen: “In contrast to the DNA-code, which is fixed, the epigenome of a person can change. By studying the epigenome, we can learn how the functioning of genes is influenced by the environment, and which factors in the environment are important”.

Traces of cigarette smoke
The researchers performed a so-called epigenome-wide association study, in which hundreds of thousands of positions in the DNA are screened to find locations where the pattern of DNA methylation differs between people with different levels of education. The new research found 58 of such locations, at genes that often had multiple functions in neuronal, immune and developmental processes. All of these locations had been reported by previous studies to differ between smokers and non-smokers. Jenny van Dongen: “We found that the epigenome of lower educated Dutch people shows more traces of cigarette smoke exposure than the epigenome of higher educated people. This pattern remained after accounting for the individual’s own smoking habits. We also found that the epigenome of lower-educated people contains more traces of second-hand smoking”.

The new research illustrates that education-associated exposures leave their traces in the  epigenome of white blood cells, with cigarette smoke being suspect number one but not the only one. The study also revealed greater traces of fine matter air pollution in the epigenome of higher educated people, but this relationship was weaker than the relationship between lower education and smoking. Senior author Dorret Boomsma: “The next challenges now are to distinguish between differential methylation as a cause or consequence of educational level and smoking. The important next  step that the researchers also should investigate is: What are the consequences of these epigenetic changes for cognitive and physical health?”

The results of the study published today are also available in an online catalogue from BBMRI-NL, a large collaboration between biobanks in the Netherlands.