Menopause, and the insomnia that often goes along with it, can speed ageing in women, two new studies suggest.
Chicken or the egg?
"For decades, scientists have disagreed over whether menopause causes ageing or ageing causes menopause," said Steve Horvath, senior author of both papers.
"It's like the chicken or the egg: which came first? Our study is the first to demonstrate that menopause makes you age faster," said Horvath, a professor of human genetics and biostatistics at the David Geffen School of Medicine at the University of California, Los Angeles.
He and his colleagues said they found that menopause boosts cellular ageing by an average of 6 percent.
"That doesn't sound like much, but it adds up over a woman's life span," Horvath added in a UCLA news release.
Read: How menopause harms the body
For example, a woman who began early menopause at age 42 would be a full year older biologically at age 50 than a woman that same age who began menopause at age 50.
Repeated waking at night
Insomnia, which often accompanies menopause, can also lead to faster biological ageing, according to the second study.
"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," said Judith Carroll. She is an assistant professor of psychiatry at UCLA's Semel Institute for Neuroscience and Human Behaviour, and first author of the sleep study.
"In the women we studied, those reporting symptoms such as restless sleep, waking repeatedly at night, having difficulty falling asleep and waking too early in the morning tended to be older biologically than women of similar chronological age who reported no symptoms," she said.
The studies included more than 5,000 women and were published in the journals Proceedings of the National Academy of Sciences and Biological Psychiatry.
What is menopause?
Symptoms of menopause
Causes of menopause