Reacción a "Reactions: exposure to urban green spaces is associated with slower epigenetic ageing "

The CARDIA study, on which these data are based, is a very high quality cardiovascular study. It is one of the few studies where we can follow people over a long period of time with information about their place of residence, greenery and parks, etc. It seems that the methods and measures are adequate. These kinds of observational studies always have a number of underlying limitations that are difficult to cover, but I think the authors have done a good job with these limitations and, more importantly, they have a very unique data set (20-year residential history and epigenetics). I think it is a very novel study.  

The work is very consistent with the existing evidence that green space is important for our health. It is also consistent with the idea that green space is even more important for low-income people, a phenomenon we call the 'equigenetic hypothesis', the main idea being that parks are especially beneficial for low-income people.  

We can't assign causality [based] on these results, but they point us to some important ideas about how green space might influence our health. It continues to confirm something we have been observing for a long time: green spaces are important for health. This study is more methodologically refined, measuring a much more proximal outcome variable (epigenetic affect).  

I don't see why the results could not be extrapolated to Spain. The important thing is that these studies on greenness are usually quite sensitive to the climate of each area (because the basal greenness varies a lot based on the climate of each area, of course: Asturias is different from Almeria. In this case they use four very different cities: Oakland in California as a more temperate area with a climate similar to the Mediterranean, Chicago and Minneapolis as areas with cold winters, and Birmingham, Alabama as a much warmer and more humid subtropical area.