Mario Fernández Fraga
Research Professor at the CINN-CSIC and head of the Cancer Epigenetics and Nanomedicine group at the Institute for Health Research of the Principality of Asturias (ISPA)
From a methodological point of view, the study is correct. It uses a good cohort and uses appropriate techniques to calculate methylation age. Methylation age can reflect biological age, and the deviation between actual chronological age - the age marked by your date of birth - and biological age is linked to lifestyle, whether you take care of yourself or not. With many nuances, biological age is also associated with health status.
Steve Horvath is an American mathematician who, using DNA methylation data, discovered a number of sites in DNA whose methylation status correlates very well with an individual's chronological age. Horvath's work had a huge impact on our field [about 10 years ago]; until then, telomere shortening was used [to measure biological age].
In this study, the team uses people's DNA methylation data [from a UK database] to calculate their methylation clocks. Looking for associations between different variables, they conclude that living in rented accommodation is associated with higher biological age than living in a home of one's own. Although I do not know enough about the situation in the UK and I am not a specialist in social sciences, I do not think it is realistic to extrapolate the results to Spain because each country has different socio-economic circumstances.
I think this study is an interesting example of how our genes interact with the environment and chance to determine who we are at each moment of our lives. However, it should be noted that this is an observational study and therefore does not demonstrate a cause-effect relationship. Moreover, although the authors have taken into account other variables (such as socio-economic status), we cannot rule out that there are others involved that have not been taken into account.