Eating well, exercising and attending regular doctor appointments can support a long healthy life, but a new study identified one possible factor beyond our control: whether you had a grandparent who went to college. The study, from researchers at Drexel University and colleagues from the University of California and the University of North Carolina, was recently published in the journal Social Science and Medicine.
Studying data across three generations – education of parents and grandparents, and health data from parents and their children – the group found a statistically significant association between grandparents' education level and their grandchildren's epigenetic-based "real" age (short definition of what is meant by "real" (how old an individual is based on their health profile and cells).
The study's finding that grandchildren of college-educated grandparents showed slower biological aging (i.e., younger biological age relative to chronological age) than those whose grandparents did not graduate from college is based on five different epigenetic-based aging clocks. These clocks use a saliva swab to examine a biological process known as DNA methylation – which changes as the body ages – to predict an individual's age based on their health profile at the cellular level.
"The research community has established a link between how social factors, socioeconomic factors, and childhood adversity can contribute to health trajectories," said lead author Agus Surachman, PhD, an assistant professor in the Dornsife School of Public Health, who completed his research for the study during his time as a postdoctoral scholar at University of California, San Francisco. "We know from animal studies that health is transmitted across several generations, from grandparents to grandchildren. But we now have robust human data that shows that not only do parents' socioeconomic factors play a role in their children's health, but that influence goes back an extra generation as well."
Previous human studies in this area found that exposure to traumatic experiences, such as the Holocaust and Tutsi genocide, can influence the methylation of genes among survivors and their children. The data in this study fills an important gap by examining a general population, and a common crude index of social stress exposures -- level of education. The authors say parents' education level is a useful metric for children's early life socioeconomic status and exposure to social stressors.
"Parental early life socioeconomic advantages may be associated with better health profile of their offspring through epigenetic mechanisms, especially through the maternal line," said Surachman. "This understanding about the intergenerational nature of transmission of social advantages and health should make us re-think our values. I'd like to see more resources invested in education and health, a factor which shapes offspring health before we are even born."
Epigenetic clocks are promising tools for estimating length of life, and can offer insights about the risk for chronic disease and other health outcomes. Tests can cost consumers hundreds of dollars, but experts say the cost may go down as the technology improves.
Mothers were recruited to the NHLBI Growth and Health Study (NGHS 1) when they were 9-10 years old, and then re-recruited three decades later for the National Growth and Health Study (NGHS 2), to gather health and education information and the health information to determine their youngest child's (ages 2-17) epigenetic aging, or biological age.
The researchers controlled for other factors that may influence child health, such as age of the grandchildren, sex, children's body-mass index (BMI), and characteristics of the mother – the mother's childhood family structure, mother's health profile and the mother's marital status.
The team also wanted to understand what could help explain the intergenerational transmission -- if the health of the mother might help explain the transmission effect between grandparent education and grandchild biological age. They used mother's childhood and adult health data, measuring factors like BMI, cardiovascular health and adult c-reactive protein to measure body inflammation and found that the health of the mother explained a small amount of the link between grandparents' education and epigenetic age of their grandchildren (14.5% to be exact).
"The link between a grandparent's socioeconomic status and a grandchild's epigenetic age is a remarkable finding, across generations," said senior author Elissa Epel, PhD, a professor at the University of California, San Francisco. "This opens up a myriad of possible explanations and will need to be replicated. For now, we know that the mother's poorer metabolic health is a partial mediator of this relationship."
The authors are following this cohort to examine grandparent and parent predictors of the offspring as they reach adulthood. They are also looking at social and psychological factors of accelerated epigenetic aging in samples with chronic conditions, including breast cancer survivors and chronic kidney disease. However, more research is needed to examine the myriad of factors that influence health trajectories of youth, the authors caution.
"In the United States, we tend to over-emphasize individual responsibility when it comes to health —and there's a lot of blaming people for their poor health," said Surachman. "But the reality is that health is much more complex than that. Some factors are simply beyond our control, such as the genetics and the inherited epigenetics we are born with. I hope this helps us give more grace and compassion to ourselves and our communities."
In addition to Surachman and Epel, other authors on the paper include Elissa Hamlat of the University of California San Francisco, Anthony S. Zannas of the University of North Carolina Chapel Hill, Steve Horvath of University of California Los Angeles and Barbara Laraia of the University of California Berkeley.
Support for the study came from the Drexel FIRST (Faculty Institutional Recruitment for Sustainable Transformation) Program, National Institutes of Health grant U54CA267735-02, the Eunice Kennedy Shriver National Institute of Child Health and Human Development grant [R01HD073568], a National Heart, Lung, and Blood Institute grant [R56HL141878], grants from the National Institute on Aging [R56AG059677 & R01AG059677], and by the LSP Family Foundation.
The paper, Grandparents' educational attainment is associated with grandchildren's epigenetic-based age acceleration in the National Growth and Health Study, is available online here.
