"Our study is the first to demonstrate that menopause makes you age faster."
Women who enter menopause early may age faster than women in whom menopause arrives later, said a study Monday that could help pinpoint women at highest risk of age-related diseases.
The findings could settle a long-standing debate, said Steve Horvath, a professor of human genetics and biostatistics at the David Geffen School of Medicine at the University of California, Los Angeles.
"For decades, scientists have disagreed over whether menopause causes aging or aging causes menopause," said Horvath, senior author of the study in the Proceedings of the National Academy of Sciences.
"It's like the chicken or the egg: which came first? Our study is the first to demonstrate that menopause makes you age faster."
Horvath and colleagues analyzed DNA samples of more than 3,100 women in a 15-year study of post-menopausal women, known as the Women's Health Initiative.
Measuring the biological age of cells from blood, saliva and inside the cheek, they were able to pin down the relationship between each woman's chronological age and her body's biological age.
"We discovered that menopause speeds up cellular aging by an average of six percent," said Horvath.
"That doesn't sound like much but it adds up over a woman's lifespan."
For example, a woman who enters early menopause at age 42 would age more rapidly over the next eight years than a woman who entered menopause at age 50.
By the time the 42-year-old reached age 50, her body would be biologically a year older than a woman who began menopause at 50, said the report.
Since blood appears to age faster once menopause kicks in, the rest of the body is likely deteriorating faster too, with possible implications for disease.
But Horvath said the news isn't all bad for women. Someday, doctors may use women's epigenetic clock -- tracking changes to DNA over time -- to help decide on treatments such as hormone therapy.
"No longer will researchers need to follow patients for years to track their health and occurrence of diseases," he said.
"Instead we can use the epigenetic clock to monitor their cells' aging rate and to evaluate which therapies slow the biological aging process," he added.
"This could greatly reduce the length and costs of clinical trials and speed benefits to women."