NEW YORK – Measures of epigenetic aging can help predict health outcomes and mortality in older individuals, but they work no better than other predictors, according to a new study led by researchers at the University of Southern California and elsewhere.
Past studies have shown that DNA methylation patterns are associated with various aging phenotypes, and scientists have devised different "epigenetic clocks" to measure biological aging. The USC team wanted to find out if such epigenetic aging measures could accurately predict health outcomes in older persons, similar to other predictors such as demographics, education, mental health, age, sex, and health behaviors such as smoking and drinking.
"Utility of epigenetic measures of aging in predicting the most important set of age-related health outcomes in conjunction with socioeconomic factors in a large, representative sample of older persons is unknown," the authors wrote.
For their study, published in the Proceedings of the National Academy of Sciences on Tuesday, the researchers, led by Eileen Crimmins, a professor of gerontology at USC, analyzed DNA methylation data from blood samples of almost 3,600 participants in the Health and Retirement Study. The longitudinal study includes more than 43,000 people over the age of 50 from diverse backgrounds in the US and collected data such as income, education status, cholesterol levels, and hypertension. The study also had health outcomes and mortality rates available two to four years after participants' blood was analyzed.
Looking at different epigenetic clocks that were trained on various biological phenotypes, the researchers found that some were predictive of multimorbidity after two years, and others of four-year mortality.
However, epigenetic changes only explained about 5 percent of variability in mortality and morbidity between participants, according to Crimmins. "So, it is one piece of the puzzle, but it's not the whole thing," she said.
"There are people who say, 'go get your epigenetic data, and you'll know exactly what's in store for you.' We think it will give you one clue, but there's a whole lot of other things that also are going to go into that prediction of what's going to happen," she added.
Crimmins said the study was among the first few that looked at epigenetic changes in an older population. "Our findings move the field forward by saying, yes, epigenetic change is a contributor to understanding health outcomes in real populations with real population characteristics," she said. "But it also indicates that we have more than one way to really understand all the variability that exists."
According to the authors, more work is needed to replicate the results in other cohorts and to determine whether DNA methylation-based age acceleration measures are more informative in specific subgroups.
"While the usefulness of DNA [methylation]-based age acceleration as a predictor of later life health outcomes is quite clear, other factors such as demographics, [socioeconomic status], mental health, and health behaviors remain equally, if not more robust, predictors of later life outcomes." they wrote.