Menopause could hasten aging among women, two new studies found.
"For decades, scientists have disagreed over whether menopause causes aging or aging causes menopause," Steve Horvath, professor of human genetics and biostatistics at the David Geffen School of Medicine at the University of California, Los Angeles (UCLA) and senior author of both studies, said in a press release.
"It's like the chicken or the egg: which came first? Our study is the first to demonstrate that menopause makes you age faster."
According to the researchers, insomnia that often accompanies menopause also triggers age-related changes in women, and that these factors could contribute to an increase risk for aging-related diseases and earlier death.
"Not getting restorative sleep may do more than just affect our functioning the next day; it might also influence the rate at which our biological clock ticks," Judith Carroll, assistant professor of psychiatry at the UCLA Semel Institute for Neuroscience and Human Behavior and the first author of the insomnia study, said in the same statement.
In both studies, which were respectively published in the Proceedings of the National Academy of Sciences and Biological Psychiatry, the researchers used a "biological clock," which has become a widely used method for tracking the epigenetic shift in the genome.
For the first study, the researchers analyzed the DNA of over 3,100 women and explored the relationship between each participant's chronological age (person's age measured by years) and the body's biological age using DNA samples taken from blood, saliva and cheek tissue.
Using Horvath's "biological clock," the researchers analyzed changes in the DNA called epigenetic alterations. The researchers found that menopause speeds up the aging of cells by 6 percent.
"On average, the younger a woman is when she enters menopause, the faster her blood ages," Morgan Levine, co-author of the study, said in the same statement.
"This is significant because a person's blood may mirror what's happening in other parts of the body, which could have implications for death and disease risk."
In the other study, Carroll and another group of UCLA researchers gathered data from over 2,000 women. Using the biological clock, the researchers found that postmenopausal women with insomnia symptoms were nearly two years older than their biological age compared with women of the same chronological age without insomnia symptoms.
The research teams suggest using the epigenetic clock in diagnosing hormone therapies for menopausal women, adding that this could reduce the length and costs of clinical trials for women.