Epigenetics stands among many sets of biological mechanisms that may be useful to researchers working in public health. It may be specifically interesting because:
- It is a set of upstream intracellular biological mechanisms that may be environmentally driven
- It affects gene expression
- It potentially affects many downstream biological systems
- It may offer plausible explanations about why genetics appears to explain so little about health & disease
- It may be heritable (‘environmental’ intergenerational transmissions)
- It may be reversible (interventions?)
What is epigenetics?
Epigenetics is fashionable in epidemiology, and the vocabulary surrounding it is now passing into popular culture. I have seen it mentioned in self-help pamphlets and advice on general health to the public.
Here is a definition of epigenetics we used in a paper:
Epigenetics refers to any information heritable during cell division other than the DNA sequence itself (Feinberg 2007). McGowan and Szyf (2010) have used the following definition ‘‘the combination of mechanisms that confer long-term programming to genes and could bring about a change in gene function without changing gene sequence’’ (McGowan and Szyf 2010). The most well-established epigenetic methylation modification has been observed whereby a methyl group is added to DNA. Methylation of critical regulatory regions affects gene expression, hypermethylation is usually associated with the silencing of genes whereas hypomethylation with gene activation. This alteration can be stable, and long-term but also reversible due to the existence of DNA demethylases. Epigenetic processes are therefore essential for understanding gene function and expression (Hochberg et al. 2011).
Epigenetics is interesting to me as a social epidemiologist if it is socially-driven. This provides evidence that the social and psychosocial environments affect our biological processes.
Here are some examples of papers where socially-driven epigenetics are being explored:
- McGuinness et al 2012 Int J Epi Global DNA hypomethylation observed in socio-economically deprived subjects & manual worker status. Global DNA methylation associated with biomarkers of cardiovascular disease and inflammation, after adjusting for socio-economic factors
- Tehranifar 2013 Epigenetics Low family income at birth was associated with higher Sat2 methylation and single parent family was associated with higher Alu methylation
- Borghol et al 2012 Int J Epi Adult blood DNA methylation associated with childhood socioeconomic position. “Organization of these associations across the genome suggests a well-defined epigenetic pattern linked to early socio-economic environment”
- Suderman et al 2014 BMC Med Genomics Observed genome-wide methylation profiles in adult DNA associated with childhood abuse
“Observations for child abuse showed little overlap with methylation patterns associated with socioeconomic position”
Usually the hypothesised mechanism being explored or used to explain the observation is ‘early life or in utero programming’, which is a sensitive period mechanism in terms of lifecourse epidemiology.
Epigenetics and public health: the good, the bad & the ugly
Research in social epidemiology using epigenetics has its uses and also its downsides. Here are a few I can think of
Epigenetics may facilitate the identification of environmental factors that can be modified to improve population health – and reduce health inequalities. Epigenetic mechanisms may provide steps forward in:
- Understanding which elements within our environment are implicated in epigenetic modifications
- Understanding the ‘causal chains’ between these environmental factors
- Understanding how the environmental factors affect epigenetic mechanisms differently across the lifecourse
The (somewhat cynical) good
Socially driven epigenetics acts as compelling evidence that our environments affect our health which might be helpful for:
- Convincing research institutions to fund research on health inequalities
- Convincing other researchers of the value of working on health inequalities
- Convincing policy makers to fund initiatives to improve environments for population wellbeing
So this is a rather cynical use of epigenetics or many other biological processes in social epidemiology. To be blunt, biological mechanisms & “hard scientific facts” convince people better than “wishy washy social science”. This is not the ‘fault’ of biologists or other scientists, but rather the way that the sciences are used, funded and perceived by wider society.
Using any biological mechanisms within public health research can backfire. In my experience biology is often equated with genetics. Epigenetics is therefore conflated with genetics. Many people, even within science, attribute biological processes to being genetic, and then the assumption is that nothing can be done to change the health outcome. For example, the rise in the prevalence of obesity is often discussed in terms of biological processes, epigenetics and even genetics. The conclusion is often fatalistic – we are getting fatter because of our genes – so there is nothing to be done.
Another downside is that public health messages can become diluted when the ‘hard sciences’ get involved. I notice when presenting work that refers to, or uses biological processes that I spend a large amount of time explaining the process, the methods and the interpretation of the biological result. This usually takes us away from the original point of the work. With epigenetics, a focus is put on the details of the epigenetic methods, techniques and mechanisms and not so much on the environmental factors. This can lead to the flawed conclusion that modifications should be made to biology not to the environment: “Can we develop a pill for that?”
Above are some examples of headlines that made it into the mainstream media based on research using social epigenetics. The popular media’s taste for a good headline results in the stigmatisation of population subgroups. Could epigenetic research in public health sometimes exacerbate inequalities?
I would say that epigenetics is a useful tool with interesting properties for studying socially-driven mechanisms. However, caution is needed for researchers. Through some of its uses there is a risk of further marginalising the social sciences, and most importantly a risk of sending out stigmatising messages to policy makers & the public.
This piece stems from a workshop that took place in Toulouse last spring. I was asked to provide a “social epidemiologist’s view of epigenetics”. So here, I have given my own view of epigenetics and how it relates to the type of research I am involved in.