Living conditions during childhood may have a long-term effect on DNA, according to new research by British and Canadian scientists. The findings, published in the International Journal of Epidemiology, may explain why some people who grow up in socioeconomic deprivation have health disadvantages later in life, despite improvements in their living conditions in adulthood.
Although your genes cannot be altered, the way in which they are turned on and off during your lifetime can be modified by epigenetic mechanisms. This study, carried out by scientists from McGill University and the University of British Columbia, Canada, and the UCL Institute of Child Health, UK, looked at one of these mechanisms, DNA methylation. Broadly speaking, methylation of a gene at a significant point in its DNA sequence reduces the gene's activity.
'We found a surprising amount of variation in DNA methylation – over 6,000 gene control regions showed clear differences between the 40 research participants', said co-author Professor Marcus Pembrey, from the UCL Institute of Child Health.
The researchers compared the methylation status of roughly 20,000 genes in 45-year-old adults who had very deprived living conditions during their childhood with those in adults who had very wealthy and well provided for upbringings. They found 1252 differences between the two groups. This was significantly more than the 545 differences they observed when they compared groups with different socioeconomic circumstances in adulthood.
The study did not look at links between specific diseases and DNA methylation, nor did it assess whether methylation status was associated with protective or damaging effects on health. However, the methylation differences identified between socioeconomic groups were clustered in particular areas of DNA, indicating a pattern that might be linked to health in later life.
Professor Chris Power, a member of the research term at the UCL Institute of Child Health, explained: 'The adult diseases already known to be associated with early life disadvantage include coronary heart disease, type 2 diabetes and respiratory disorders… it is hoped that future research will define which network of genes showing methylation differences are in turn associated with particular diseases'.
Forty men were invited to take part in the study, selected from a group of more than 17,000 people born during the same week in March 1958, and were enrolled in a life-long health study. The men were selected based on extreme (either poor or wealthy) standards of living in childhood, which was assessed by looking at the wealth, housing conditions and occupation of their parents.
'The current research represents just a beginning because it cannot tell us precisely when in early life these [methylation] patterns arose or what the long-term health effects will be', said Professor Power: 'This knowledge will be needed before useful interventions can be considered, but that must be the long term aim'.