Bad sleep makes people feel as if they'd aged a decade.
Poor sleep makes people feel older
Experts carried out two studies to discover if a lack of sleep could determine how old somebody feels.
429 participants were asked to record their self-perceived age over a period of 30 days and how many nights they had had insufficient rest.
Analysis revealed that for each additional day of insufficient sleep, subjective age increased by 0.23 years.
Then, 182 individuals were enrolled in a sleep restriction study where they were only allowed four hours in bed over two nights.
This made people feel 4.44 years older compared to those who got nine hours of shuteye.
Scientists at the Karolinska Institute in Sweden said: "Many people feel younger than their calendar age.
"While this phenomenon is less prevalent among younger individuals, as we venture into our thirties and beyond the discrepancy between how old we are and how old we feel becomes more pronounced.
"Emerging research suggests that our sleep habits may play a role in shaping how old we feel."