Lack of sleep linked to Alzheimer’s: Study

The findings suggested that sleep loss increases the level of a protein--known as amyloid-beta--linked to forming plaques which accumulate in the brain of Alzheimer's patients. Amyloid-beta twists into a sticky form and clumps together, forming such plaques in the brain.

“This is the first experimental study that clearly shows that disrupted sleep may contribute to the disease process,” says Peter Meerlo, a neuroscientist at the University of Groningen in the Netherlands.

Experiment conducted on mice
A team led by David Holtzman conducted an experiment on mice to measure the level of amyloid-beta in the brain fluid using a method called micro dialysis -- a technique used to determine the chemical components of the fluid in the outer space of tissues.

David Holtzman is a neurologist and neuroscientist at Washington University in St. Louis.

The experiment was carried out for three weeks wherein some mice were allowed to sleep for four hours while others slept normally.

The team found that the levels of the protein released into brain fluid of mice kept rising and falling throughout the day. It increased during the night--when mice are mostly awake--and fell during daytime when mice sleep.

The researchers noted that more Alzheimer’s plaques were made in the sleep deprived mice than others.

The mice were also given a shot of a hormone called orexin, which promotes wakefulness. The team noted that the hormone also caused amyloid-beta levels to increase. However, blocking the orexin’s activity decreased the level of protein in the brain fluid of the mice.

Pattern similar to that observed in the mice was found when the researchers measured amyloid-beta levels in the cerebral spinal fluid of some healthy young people.

Adequate sleep essential for Alzheimer’s patients
The study laid huge emphasis on the fact that sufficient sleep is very important for Alzheimer's patients.

The researchers couldn’t exactly find a link between Alzheimer’s disease and chronic sleep loss among humans. However, lead researcher Holtzman contemplated that lack of sleep could accelerate the onset of the disease, particularly in the middle-aged people.

“Mechanistically we don’t understand why [sleep] is manipulating amyloid-beta rhythms,” said Sangram Sisodia, a molecular neurobiologist at the University of Chicago, “but we do know it’s doing something good for the brain.… There’s a clear message here about why it is so important to sleep.”

The study appears online in the journal Science.