The new study, published in the Proceedings of the National Academy of Sciences, suggests that stressful events in childhood significantly predicted chromosomal differences in adulthood associated with aging. In other words, when certain bad things happened to people as children, their adult bodies showed structural damage.
Telomeres are DNA protein caps found on the end of chromosomes that protect genetic materials. As people age, their telomeres get shorter. Generally speaking, longer telomeres are associated with health and youth, while shorter ones are associated with stress, disease, and old age.
A kinesiologist from the University of British Columbia teamed up with psychologists, epidemiologists, and demographers to analyze data from a 16-year US health and retirement study. Using the study’s responses, they quantified cumulative childhood and adulthood adversity ranging from financial to social experiences and compared those to the telomere length taken from respondents’ saliva samples. The results suggested “that the shadow of childhood adversity may reach far into later adulthood in part through cellular aging,” the authors said.
The team examined responses to questions and saliva samples of nearly 4,600 retired American adults, categorizing their life experiences into seven adulthood and childhood categories. The adult difficulties ranged from losing a job, a spouse, or a child to being wounded in combat or surviving a natural disaster. Childhood struggles included having a parent with alcohol or substance abuse problems, growing up in a family needing financial assistance from relatives, physical abuse, or getting into trouble at school or with the police.
The researchers isolated which life stresses were linked to telomere length by comparing respondents’ reports to each other and the salivary samples and running a statistical analysis.
They found that a single adverse event didn’t tend to have a significant relationship with telomere length, but cumulative adversity over a lifetime predicted 6% higher odds of shorter telomere length, mainly due to childhood adversity. Four adverse events in childhood appeared to impact telomere length in the adult respondents: having parents with alcohol and substance abuse problems, being physically abused, repeating a year of school, and getting in trouble with the police.
Respondents who experienced certain childhood difficulties revealed shorter telomeres in their saliva samples than respondents who didn’t report having these difficult experiences. Each additional childhood event predicted 11% higher odds of having short telomeres, the researchers noted, and this was linked mainly to social and traumatic events rather than financial ones. (Other evidence has suggested that childhood poverty has a negative impact on DNA.) “Childhood social adversity—beyond socioeconomic position (parental income, employment, and education)—are especially salient to adulthood health and should be targets for intervention,” the researchers wrote.
Though scientists have linked telomere length with youth and strength, how precisely adversity impacts the protein caps isn’t yet understood. The researchers said they believe that adversity tinkers with the epigenome, the genome’s control system, and alters “gene expression almost permanently.”
Still, the effects of a difficult childhood are not necessarily set in stone. For instance, other data has shown that exercising after age 40 is linked to longer telomeres.