News — UCLA geneticist led a team of 65 scientists in seven countries to record age-related changes to human DNA, calculate biological age and estimate a person鈥檚 lifespan. A higher biological age鈥攔egardless of chronological age鈥攃onsistently predicted an earlier death.
The findings are published in today鈥檚 edition of the journal Aging.
鈥淥ur research reveals valuable clues into what causes human aging, marking a first step toward developing targeted methods to slow the process,鈥� said principal investigator Horvath, a professor of human genetics and biostatistics at UCLA鈥檚 and .
Drawing on 13 sets of data, including the landmark Framingham Heart Study and Women鈥檚 Health Initiative, a consortium of 25 institutions analyzed the DNA in blood samples collected from more than 13,000 people in the United States and Europe.
Applying a variety of molecular methods, including an developed by Horvath in 2013, the scientists measured the aging rates of each individual. The clock calculates the aging of blood and other tissues by tracking methylation, a natural process that chemically alters DNA over time. By comparing chronological age to the blood鈥檚 biological age, the scientists used the clock to predict each person鈥檚 life expectancy.
鈥淲e were stunned to see that the epigenetic clock was able to predict the lifespans of Caucasians, Hispanics and African-Americans,鈥� said first author , a postdoctoral fellow at the National Institute on Aging. 鈥淭his rang true even after adjusting for traditional risk factors like age, gender, smoking, body-mass index, disease history and blood cell counts.鈥�
The group鈥檚 findings, however, don鈥檛 bode well for everyone.
鈥淲e discovered that 5 percent of the population ages at a faster biological rate, resulting in a shorter life expectancy,鈥� Horvath said. 鈥淎ccelerated aging increases these adults鈥� risk of death by 50 percent at any age.鈥�
For example, two 60-year-old men, Peter and Joe, both smoke to deal with high stress. Peter鈥檚 epigenetic aging rate ranks in the top 5 percent, while Joe鈥檚 aging rate is average. The likelihood of Peter dying within the next 10 years is 75 percent compared to 60 percent for Joe.
The preliminary finding may explain why some individuals die young 鈥� even when they follow a nutritious diet, exercise regularly, drink in moderation and don鈥檛 smoke. 鈥淲hile a healthful lifestyle may help extend life expectancy, our innate aging process prevents us from cheating death forever,鈥� Horvath emphasized. 鈥淵et risk factors like smoking, diabetes and high blood pressure still predict mortality more strongly than one鈥檚 epigenetic aging rate.鈥�
Scientists have long searched to identify biomarkers for biological age, according to coauthor , a professor at Harvard Medical School and a senior scientist for the Institute of Aging Research at Hebrew SeniorLife.
鈥淚n geriatric medicine, we are always struck by the difference between our patients鈥� chronological age and how old they appear physiologically,鈥� said Kiel. 鈥淭his study validates the use of DNA methylation as a biomarker for biological age. And if we can prove that DNA methylation accelerates aging, we can devise strategies to slow the rate and maximize a person鈥檚 years of good health.鈥�
The precise role of epigenetic changes in aging and death, however, remains unknown, said coauthor , an assistant professor of cardiovascular medicine at Stanford University School of Medicine.
鈥淒o the epigenetic changes associated with chronological aging directly cause death in older people?鈥� said Assimes. 鈥淧erhaps they merely enhance the development of certain diseases--or cripple one鈥檚 ability to resist the progression of disease after it has taken root. Future research is needed to address these questions.鈥�
Larger studies focused only on cases with well-documented causes of death will help scientists tease out the relationship between epigenetic age and specific diseases, he added.
By 2017, according to the , the number of people worldwide over age 65 will outnumber those under age 5 for the first time in recorded history. By 2050, the proportion of the global population over 60 will double from 11 to 22 percent. Many countries will be ill-prepared to keep pace with the high costs associated with disease and disability as more people live longer, said Horvath.
鈥淲e must find interventions that prolong healthy living by five to 20 years. We don鈥檛 have time, however, to follow a person for decades to test whether a new drug works.鈥� said Horvath. 鈥淭he epigenetic clock would allow scientists to quickly evaluate the effect of anti-aging therapies in only three years.鈥�
The University of California has applied for a provisional patent on the epigenetic clock.
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