PARIS (AFP) -- Swedish scientists say they had found further evidence that sleep helps to promote the health of brain cells.

The clues come in two so-called biomarkers -- tell-tales of biological activity -- found in the blood of sleep-deprived young men.

A team at Uppsala University recruited 15 healthy volunteers, and deprived them of sleep for a night or let them sleep for eight hours.

Among those who went without sleep, blood tests showed a roughly 20-per-cent increase in signature molecules called neuron-specific enolase, or NSE, and S-100 calcium-binding protein B, or S-100B.

"These brain molecules typically rise in blood under conditions of brain damage," said neuroscientist Christian Benedict.

"A lack of sleep may promote neurodegenerative processes... (while) a good night's sleep may be critical for maintaining brain health."

The paper, published Tuesday in the specialist journal Sleep, follows an investigation published in the U.S. journal Science in October that found sleep accelerated the cleansing of cellular waste from the brain.

The detritus includes amyloid beta, a protein that, when accumulated is a driver of Alzheimer's disease, according to the probe, which was conducted on mice.