How Sleep Nurtures Your Brain

By Michael Lasalandra
BIDMC Correspondent

Getting the proper amount of sleep each night doesn’t just help us operate at peak efficiency the next day…it also nurtures the brain itself.

A study this year by researchers in England found that sleep is important to maintaining the health or our brain’s neurons, in that it allows them to independently rest and repair themselves. Neurons can’t rest while we are awake, they noted. If they try to, brain performance is affected negatively.

“It is similar to a complex machine with multiple interactive components,” says Dr. Robert Thomas, a sleep medicine physician and co-director of the Sleep Disorders Clinic at Beth Israel Deaconess Medical Center. “If a machine keeps running and running, it gets damaged.

“All the nerve cells in the brain are highly connected,” he says. “When you are awake you form connections between neurons. But you can’t keep doing it.”

The connections change in shape and size as the cells serve their purpose, he says. But all that activity during wakefulness leaves debris – byproducts of normal activity. ”As the cells expend energy and perform, they show evidence of stress, energy deficits and accumulate biological junk,” he says. “That junk has to be cleaned out. Sleep serves that vital housekeeping function. The less important new connections also need to be removed.”

“Sleep allows large numbers of neurons to go off line,” says Dr. Thomas. “They shut down and come back on line again, fluctuating between ‘on’ and ‘off’ periods lasting a little less than a second, during sleep.”

While at rest, the brain also grows new neurons, says Dr. Thomas, who is also an associate professor of medicine at Harvard Medical School.

“Sleep restores and resets numerous systems, such as metabolic, autonomic, endocrine and metabolic,” he adds. “Sleep prepares you for your next bout of wakefulness.”

The body and the brain are highly interconnected,” he notes. “Sleep is essential for health. Without proper sleep, everything starts falling apart.”
 
If one stays awake for 24 hours, “different parts of the brain will slow down and go intermittently off-line even when we are technically ‘awake,’ ” he says.

Studies show that sleep-deprived people perform as poorly on driving simulators or hand-eye coordination tests as those who are under the influence of alcohol.

It is not known if brain cells will die with sleep deprivation, but formation of new nerve cells is affected, he says. “If you mess with sleep, you may not regenerate your brain as well.”

Studies on rats show they will die if deprived of sufficient sleep, he says. “The immune system weakens,” he explains.

Another new study, in the Journal of Neuroscience, was conducted in mice that were either allowed to sleep or forced to stay awake. The study, done at the University of Wisconsin, found that sleep or the lack of it affected gene activity of cells called oligodendrocytes, which are involved in the production of myelin. Myelin covers brain and spinal cord nerve cells as a kind of insulation; it is considered essential to the movement of electrical signals from cell to cell.

The study shows sleep seems to turn on genes that play a role in the formation of myelin. At the same time, lack of sleep was linked to genes associated with cell stress and death.

Dr. Thomas says most people need seven or eight hours of sleep per night to function efficiently. Children need more. While most people wake up — biologically speaking — several times per night, usually these are for very brief periods and may not even be noticed. “There is a need for undisturbed sleep,” he says.

“It is like the difference between highway driving and city driving,” he says. “Highway driving is more efficient. City driving, with all its starts and stops, is less efficient and wears you out. If sleep is excessively interrupted, it cannot perform its function.”
 
Above content provided by Beth Israel Deaconess Medical Center. For advice about your medical care, consult your doctor.