Green tea may shield brain from sleep apnea effects

NEW YORK (Reuters Health) - Compounds found in green tea may help ward off the neurological damage that can come with the breathing disorder sleep apnea, a new animal study hints.

Researchers found that when they added green tea antioxidants to rats' drinking water, it appeared to protect the animals' brains during bouts of oxygen deprivation designed to mimic the effects of obstructive sleep apnea (OSA).

The findings suggest that green tea compounds should be further studied as a potential OSA therapy, the researchers report in the American Journal of Respiratory and Critical Care Medicine.

OSA is a common disorder in which soft tissues in the throat temporarily collapse and block the airway during sleep, causing repeated stops and starts in breathing throughout the night.

The immediate symptoms include chronic loud snoring and gasping, as well as daytime sleepiness. Left untreated, OSA can eventually have widespread effects in the body; it's linked to high blood pressure, and research suggests that the intermittent dips in oxygen to the brain may lead to memory and learning difficulties.

In the new study, Dr. David Gozal and colleagues at the University of Louisville School of Medicine in Kentucky looked at whether green tea compounds called catechin polyphenols could help shield the brain from this oxygen deprivation.

Catechin polyphenols act as antioxidants, which means they help neutralize cell-damaging particles called oxygen free radicals. Free radicals are normal byproducts of metabolism, but in excess they lead to a state known as oxidative stress.

It's thought that the oxygen deprivation of OSA leads to oxidative stress, and that this, at least in part, explains the cognitive problems seen in some people with the sleep disorder.

Gozal and his colleagues found that when rats were exposed to periodic bouts of oxygen deprivation over 14 days, it did boost signs of oxidative stress in the brain. This didn't happen, however, if rats had been given water containing green tea polyphenols.

What's more, compared with rats given plain water, these animals performed better on a standard test of learning and memory -- a water "maze" designed to encourage the animals to remember the location of an escape platform.

In theory, Gozal told Reuters Health, a regular cup of green tea could be beneficial, used alongside standard OSA treatment.

"However," he said, "definitive proof that green tea would help will have to await a trial in human patients."

SOURCE: American Journal of Respiratory and Critical Care Medicine, May 15, 2008