Menopause and insomnia may increase a woman's risk of ageing-related diseases and early death, new research has claimed.
Researchers found that menopause accelerates biological ageing and that insomnia, which often accompanies menopause, also has a clear association with age acceleration.
The findings, which suggest that both factors could increase women's risk for ageing-related diseases and earlier death, contribute to increasing evidence of the biological clock's variability, researchers said.
"Our study is the first to demonstrate that menopause makes you age faster," said Steve Horvath from University of California Los Angeles (UCLA) in the US.
Not getting restorative sleep may do more than just affect our functioning the next day, said Judith Carroll from UCLA.
"It might also influence the rate at which our biological clock ticks," said Carroll.
"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.
Both studies used a genetic "biological clock" developed by Horvath, which has become a widely used method for tracking the epigenetic shift in the genome.
Epigenetics is the study of changes to DNA packaging that influence which genes are expressed but do not affect the DNA sequence itself, researchers said.
In the menopause study, researchers tracked methylation, a chemical biomarker linked to ageing, to analyse DNA samples from more than 3,100 women enrolled in four large studies.
Researchers measured the biological age of cells from blood, saliva and inside the cheek, from 3,100 women to explore the relationship between each woman's chronological age and her body's biological age.
"We discovered that menopause speeds up cellular ageing by an average of six per cent. That does not sound like much but it adds up over a woman's lifespan," said Horvath.
"Take, for example, a woman who enters early menopause at age 42. Eight years later, her body would be a full year older biologically than another 50-year-old woman who entered menopause naturally at age 50," he said.
In the sleep study, researchers drew their data from more than 2,000 women.
Using the epigenetic clock, they found that postmenopausal women with five insomnia symptoms were nearly two years older biologically than women the same chronological age with no insomnia symptoms.
"We cannot conclude definitively from our study that the insomnia symptoms lead to the increased epigenetic age, but these are powerful findings," said Carroll.
The findings were published in the journals PNAS and Biological Psychiatry.
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