Sept. 24 (Bloomberg) -- Sleepless nights may lead to the development of Alzheimer’s disease over time, a study of mice suggests.

Rodents forced to stay awake showed a buildup in their brains of a protein associated with the development of Alzheimer’s in humans, said lead study author Jae-Eun Kang. The research was published today in the journal Science.

Kang said additional research in humans may explore whether chronic sleep loss in young and middle-age adults increases the risk of Alzheimer’s disease later in life. About 5.3 million Americans have Alzheimer’s, according to the Chicago-based Alzheimer’s Association advocacy group. There is no cure. Drugs sold in the U.S. can ease symptoms for about a year.

“The hope would be to show that treating sleep problems in humans is important not just for the immediate effect of having a normal life, but also for the long-term effect of having a healthier brain,” said Kang, a post-doctoral researcher at Washington University in St. Louis, in a telephone interview.

Proteins called beta amyloid accumulating in brain fluids is “a critical event” in the progression of Alzheimer’s, the study said. In a healthy brain, the protein is produced by the neurons and secreted into brain fluid. As Alzheimer’s develops over time, clumps of the protein stick together, forming plaques that erode brain function.

Forced to Stay Awake

The study tested two groups of mice for levels of the protein and found that it increased during waking hours and decreased when they slept. Protein levels also rose when the animals were forced to stay awake or when they were given injections of orexin, a molecule implicated in many sleep disorders, according to the study.

When the mice were allowed to follow their normal sleep patterns, protein levels declined.

Over 24 hours, mice typically sleep about 70 percent of the time, spread over several short spurts. In the three-week study, mice were forced out of this pattern and required to stay awake for six consecutive hours.

The number of people worldwide with the disease could reach 115.4 million by 2050, according to a report released Sept. 21 by Alzheimer’s Disease International, an advocacy group based in London.

The first symptom of Alzheimer’s may be mild forgetfulness. As the condition progresses, it begins to interfere with patients’ lives as they forget how to brush their teeth, change their clothes, or recognize once-familiar people. Eventually they require constant care, according to the National Institute on Aging in Bethesda, Maryland.

Alzheimer’s destroys brain cells progressively, making it difficult for patients to think, remember and function. The condition is still only definitively diagnosed at autopsy, when amyloid protein plaques in the brain can be seen.

The study was paid for in part by the U.S. National Institutes of Health in Bethesda, and Eli Lilly & Co., based in Indianapolis.

To contact the reporter on this story: Pat Wechsler in New York at pwechsler@bloomberg.net.

Last Updated: September 24, 2009 14:00 EDT